Accessory Dwelling Units
Accessory Dwelling Units
October 1995 - Report No. 33
Copyright © 1995 by the Municipal Research & Services Center of Washington.
All rights reserved. Except as permitted under the Copyright Act of 1976, no
part of this publication may be reproduced or distributed in any form or by
any means or stored in a data base or retrieval system without the prior permission
of the publisher, however, government entities in the State of Washington are
granted permission to reproduce and distribute this publication for official
In the 1940s and '50s, many American families rented out an extra apartment
over their garages or in the basement of their homes as a way to earn some extra
income to help with the mortgage payment or with other household expenses. In
fact, backyard cottages and attic and basement apartments were a common feature
in many communities across the country. Since then, as more communities have
adopted restrictive residential zoning regulations, such apartments, technically
known as accessory dwelling units (ADUs), have been either severely limited
or banned altogether, usually in the name of protecting single-family neighborhoods.
Recently, however, perceptions and attitudes toward accessory dwelling units
are once again beginning to change. Much of this transformation can be attributed
to the effects of the affordable housing crisis. Demographic trends that have
resulted in growing numbers of smaller households have also contributed to the
increased interest in accessory dwelling units. In addition, new growth management
laws are requiring many communities to plan for and accommodate higher housing
densities. Against this backdrop, many communities in Washington have begun
to reexamine the appropriateness of zoning regulations that severely limit or
prohibit accessory dwelling units. For cities over 20,000 in population, the
Washington Legislature has now mandated that accessory dwelling units be encouraged
and allowed in single-family zones.
What are accessory dwelling units? How can they benefit your community? How
can your community encourage accessory dwelling units in ways that protect existing
neighborhood character? This publication is intended to help local policy-makers
answer these and other questions as they consider accessory dwelling units in
Allowing accessory dwelling units in single-family neighborhoods is not a panacea
for all of a community's housing problems. They should also be considered with
a variety of other possible approaches for achieving your community's housing
goals. For more information on the many other techniques available to promote
affordable housing, see Affordable Housing Techniques - A Primer for Local
Government Officials, Municipal Research and Services Center of Washington,
Special acknowledgment is given to Byron Katsuyama, MRSC Public Policy Consultant,
who prepared this report. Thanks also to Bob Meinig, MRSC LegalConsultant, Sue
Enger, MRSC Planning Consultant, for their review and comments, and to Holly
Martin, MRSC Word Processing Specialist, for her assistance in format design
and copy preparation.
Richard Yukubousky, Executive Director
Municipal Research and Services Center of Washington
Allowing the development of accessory dwelling units, or ADUs, in single-family
homes is becoming an increasingly popular technique for creating low- and moderate-income
housing for both homeowners and renters. Homeowners benefit from the additional
rental income that they can use to pay part of their mortgage payment or to
help with the upkeep on their homes. Renters benefit from the availability of
moderately priced rental housing in single-family neighborhoods. The community
benefits from the addition of affordable housing for little or no public expense.
ADUs are most commonly understood to be a separate additional living unit,
including separate kitchen, sleeping, and bathroom facilities, attached or detached
from the primary residential unit, on a single-family lot. ADUs are usually
subordinate in size, location, and appearance to the primary unit.
Attached units, contained within a single-family home, known variously as "mother-in-law
apartments," "accessory apartments," or "second units,"
are the most common types of accessory dwelling units. Accessory apartments
usually involve the renovation of a garage, basement, attached shed, or similar
space in a single-family home.
Less common are detached "accessory cottages" or "echo homes"
(an acronym for "elder cottage housing opportunities"), which are
structurally independent from the primary residence. These units are often constructed
or installed to provide housing for elderly parents being cared for by their
adult children. Accessory cottages are permanent structures, while echo homes
are temporary and movable. [Accessory Units: An Increasing Source
of Affordable Housing, p. 5]
To reduce housing costs and meet changing market demands, pressures have increased
in recent years to allow higher densities in urban areas, make more efficient
use of existing housing stocks, and to eliminate regulatory barriers that unnecessarily
limit affordable housing opportunities. Recent state legislation has underscored
the need to review local housing needs and to plan for and take action to encourage
the development of more affordable housing. Accessory dwelling units have emerged
as an important component of the affordable housing strategies being carried
out in many Washington cities.
The purpose of this report is to help local officials as they begin to consider
proposals to allow ADUs in their communities. It is intended as a primer for
city council and planning commission members on the potential of ADUs as a source
of affordable housing and on the various regulatory issues and options that
are likely to arise as ADUs are discussed. The report begins with a discussion
of the reasons for the current interest in ADUs. It also reviews some benefits
that ADUs can provide for homeowners, renters, and the community. The remaining
sections focus on ADU policy issues and options, including a discussion of common
zoning regulations. The report also includes sample ordinance language where
Appendix A contains the text of a model accessory dwelling unit ordinance developed
by the state Department of Community, Trade, and Economic Development in consultation
with the Affordable Housing Advisory Board (created by the 1993 Housing Policy
Act). Appendix B contains a table summarizing selected ADU ordinance provisions
from 10 Washington cities. Finally, Appendix C contains some sample ADU permits
Why the Interest in ADUs?
Three factors have spurred the recent interest in accessory dwelling unitsthe
growing affordable housing crisis, changing demographics and recently adopted
state growth management and housing policies.
The Affordable Housing Crisis
The need for more affordable housing is probably the single most important
reason for the growing interest in accessory dwelling units. Several studies
by both public and private housing groups have amply documented the nature and
extent of the affordable housing crisis in Washington. Many see ADUs, which
use existing housing resources, as a simple and inexpensive way for communities
to respond to the affordable housing crisis. ADUs typically cost 25 to 40 percent
less to build than new, comparably-sized housing units since they do not require
development of new land, and because construction costs are lower. Consequently,
ADUs are usually much less expensive to rent.
There is a growing need for smaller housing. In Washington, the average household
size in 1960 was 3.09 persons. In 1990, it had declined to 2.53 persons. The
decline in average household size has resulted from several factors, including
a growing elderly population, increasing numbers of single-person households,
decreasing family size preferences, and high divorce rates.
A growing elderly population has led to an increase in the proportion of households
having only one or two persons. According to data from the 1990 census, households
with one or more persons 65 and older, make up more than 21 percent of the households
in Washington. Persons over 65 and living alone (mostly women) make up almost
9 percent of all households in the state. Many of the elderly live in homes
that have surplus space, and, while most want to stay in their homes, they often
do not need and, in some cases, can no longer take care of a large home. Adding
an ADU to their homes may allow many of these homeowners to remain in their
homes for a longer time. [Housing Affordability and Density: Regulatory Reform
and Design Recommendations, p.48]
These statistics indicate that much of our single-family housing is no
longer being used primarily by families with children in residence.
These trends call into question the emphasis that exclusive single-family
zoning has traditionally placed on promoting a life-style built
around female domesticity and childrearing. This emphasis may
have made some sense sixty years ago, when almost two-thirds of
the households living in single-family houses had children present.
But today, when less than half of them do, it is questionable
whether promoting homogeneous, family-oriented neighborhoods will
produce better residential environments, or even whether is will
bolster the family as an institution in contemporary society.
Growing numbers of single-person households have also increased the demand
for smaller housing. Households with single persons under 65 now make up almost
17% of the households in the state.
The number of single-parent households has also increased. A large part of
the growth in the numbers of these households is due to continuing high divorce
rates. Mothers with one or more children head the majority of single-parent
households. This group of single-parent households now represents almost 7 percent
of the total number of households in the state. For many single-parent households
the only options available for housing may be apartments in large complexes
that offer few amenities for families with children. [Housing Affordability
and Density: Regulatory Reform and Design Recommendations, p.47]
A decrease in family-size preferences has also contributed to the trend toward
smaller household size. Many young married couples today are waiting longer
to have children and, when they do, are usually deciding to have fewer children
than their parents. Many of these families do not need or cannot afford homes
as large as the ones that they grew up in.
One consequence of these demographic changes has been a growing need and demand
for smaller housing. Many single-parents, single-persons, and young families
either cannot afford, or do not need, a large home for themselves or their families.
At the same time, many parents of baby boomers are now empty-nesters who live
in homes that were originally built to hold families of five or six. The decline
in household size has left many of these empty-nesters and other homeowners
with unused, surplus housing space.The coincidental increase in the demand for
smaller homes and the presence of surplus housing space has led many communities
to consider ADUs as an efficient and low cost strategy for increasing affordable
While many cities in Washington have considered ordinances to allow ADUs in
the past, the Washington Growth Management Act and, more recently, the Washington
Housing Policy Act are now requiring cities to plan for and provide more affordable
housing opportunities, including ADUs, in their communities.
State Growth Management Act. The state Growth Management Act (GMA),
passed by the legislature in 1990, establishes an extensive planning and land
use regulatory framework and requires the counties (and cities within those
counties) with the greatest population growth to formulate, under guidelines
in the Act, both a comprehensive plan and development regulations in conformance
with the plan. Counties that are not required to plan under the GMA may elect
to do so.
The GMA provides that communities in developing comprehensive plans should
strive to "encourage the availability of affordable housing to all economic
segments of the population" and to "promote a variety of residential
densities and housing types, and encourage the preservation of existing housing
stock." The Act also discourages the conversion of undeveloped land "into
sprawling, low-density development." [RCW 36.70A.020]
Comprehensive plans developed under the GMA are required to have a separate
housing element that includes:
- An inventory and analysis of existing and projected housing needs;
- A statement of goals and policies for housing preservation, improvement
- Identification of sufficient land for housing, including government-assisted
housing, housing for low-income families, mobile/manufactured housing, multifamily
housing, and special needs housing; and
- A plan for meeting the housing needs of all economic segments of the community
A 1991 amendment to the GMA adds a requirement for county-wide planning policies
that must include, among other things,"policies that consider the need
for affordable housing for all economic segments of the population and parameters
for its distribution." [RCW 36.70A.210(3)(e)]
Finally, the GMA specifically encourages the use of innovative land use management
techniques to enhance affordable housing opportunities, including, "density
bonuses, cluster housing, planned unit developments, and the transfer of development
rights." [RCW 36.70A.090]
1993 Housing Policy Act. The Washington Housing Policy Act, passed by
the legislature in 1993, establishes the goals of reducing housing costs and
improving housing quality for people in all income groups. Encouraging the development
and placement of ADUs in single-family homes was recognized as an important
part of these goals.
The Act directs the state Department of Community, Trade, and Economic Development
(CTED (Dept. of Commerce)), in consultation with the affordable housing advisory board created
by the Act, to report to the legislature on the development and placement of
accessory apartments. The Act also directs CTED (Dept. of Commerce) to make recommendations to
the legislature "designed to encourage the development and placement of
accessory apartments in areas zoned for single-family residential use."
[RCW 43.63A.215(1)(b)] In response, CTED (Dept. of Commerce), along with the affordable housing
advisory board, developed a model accessory dwelling unit ordinance (see Appendix
The Act further requires that counties planning under the Growth Management
Act and cities with populations of over 20,000 adopt ordinances by the end of
1994 that incorporate the accessory apartment recommendations developed by CTED (Dept. of Commerce)
into their "development regulations, zoning regulations, or official controls."
To allow some local flexibility, the recommendations are "subject to such
regulations, conditions, procedures, and limitations as determined by the local
legislative authority." [RCW 43.63A.215(3)]
Although the cities and counties subject to the Act's requirements probably
must adopt ordinances to allow ADUs within single-family zones, the "local
flexibility" provision appears to give legislative authorities some latitude
to adapt CTED (Dept. of Commerce)'s model ordinance recommendations to the needs and preferences
of the local community. For example, while the model ordinance recommends that
ADUs be allowed in either existing or new homes, some cities have decided to
limit them to homes that are over a certain age so as to prohibit ADUs in new
construction. Similarly, while the model ordinance recommends that ADUs be allowed
as both attached and detached units, some communities have, due to local preferences
or conditions, decided to limit ADUs to units that are attached to the primary
residence. However, it is still unclear how far cities may depart from CTED (Dept. of Commerce)s
recommendations and remain in compliance with the intent of the Act
Many cities have already adopted ADU ordinances to comply with the Act, while
others are currently in the process of doing so.
ADUs can provide a surprising number of benefits to communities, homeowners
and renters. Although much of the attention given to ADUs revolves around their
potential for increasing the supply of affordable housing opportunities, ADUs
may also help to address other social issues, particularly those relating to
housing options for our growing elderly population.
ADUs Can Help to Increase the Supply of Affordable Housing Without Government
Subsidies. Allowing ADUs is one way that communities can provide more affordable
housing opportunities without the necessity of local government expenditures
or subsidies. This is a particularly good feature in view of the recent declines
in federal support for the construction of new affordable housing units. When
compared to the costs of constructing new government-subsidized apartments,
the lower cost of converting existing units, which are paid for by the homeowner,
will be an attractive option for most communities.
If 1 in every 10 of America's owner-occupied single-family homes built
before 1975 were to devote space to an accessory unit, 3.8 million
rental units would be generated, increasing the supply of rental
housing by about 10 percent.
"Not In My Backyard": Removing Barriers to Affordable Housing
Advisory Commission on Regulatory Barriers to Affordable
Housing, U.S. Department of Housing & Urban Development
ADUs also tend to be better integrated into the community, unlike other forms
of affordable housing that may be concentrated in a few areas. In most communities
this dispersion occurs without the necessity for government intervention. A
few communities, however, have adopted provisions that limit concentrations
of ADUs by controlling the number of conversions that may occur within a particular
ADUs add to affordability both from the perspective of potential tenants, for
whom rents are usually cheaper than for market units, and from the perspective
ofhomeowners, who can use the rental income from an ADU to ease the burden of
home mortgage and maintenance expenses.
ADUs Encourage Efficient Use of Existing Housing Stocks and Infrastructure.
Many homes built during the 40's, 50's, and 60's were designed to hold large
(by today's standards) households. Demographic trends since those times have
resulted in lower fertility rates, a reduction in family size preferences, and
smaller average household sizes. One consequence of these trends has been a
widespread increase in the number of homes with surplus living space. [Accessory
Apartments in Single-Family Housing, pp. 60-61]
Survey findings from the federal Housing and Urban Development Department's
American Housing Survey show that 32 percent of all homes with five or more
rooms are occupied by one- or two-person households. ["Not In My Backyard":
Removing Barriers to Affordable Housing, p. 7-13] By using surplus
space in single-family homes, ADUs promote more efficient use of the community's
existing housing stock and supporting infrastructure.
ADUs Encourage Better Housing Maintenance and Neighborhood Stability.
By allowing ADUs, communities can encourage better upkeep of the existing housing
stock since homeowners can apply a portion of the income from their rental unit
to maintaining their property. Homeowners can also exchange rent reductions
for maintenance services by tenants.
ADUs also help to enhance neighborhood stability since they can provide homeowners
(e.g., elderly homeowners on fixed incomes and single parents with low incomes)
with the extra income they may need to remain in their homes for longer periods.
ADUs Can Help to Meet Growth Management Goals by Creating More Housing Opportunities
Within Existing Urban Areas. A fundamental principle of the state Growth
Management Act is to steer new growth to areas that are already urban or urbanizing.
Using surplus space in existing housing is one way that communities can take
action to meet regional growth management goals to conserve land, house more
people within urban growth areas, and prevent more sprawl.
ADUs Make it Possible for Adult Children to Provide Care and Support to
a Parent in a Semi-Independent Living Arrangement. Many baby boomers
are now facing the prospect of having to arrange for the care and housing of
their aging parents or other close relatives. By allowing ADUs, the community
can give these families the option of providing for either live-in care in their
parents house or of having their parents move in with them. With an ADU
in their home, adult children can care for an aging parent while retaining a
semi-independent living arrangement both for themselves and their parents.
ADUs Can Provide Homeowners with Extra Income to Help Meet Rising Homeownership
Costs. ADUs can provide many homeowners with needed additional income to
meet high mortgage and maintenance costs. For a young family in their first
home or for a single parent after a divorce, the additional income froman ADU
may spell the difference between being able and not being able to stay in their
The additional income from an ADU may be particularly helpful for many elderly
homeowners who are living on fixed incomes. Contrary to popular notions, most
elderly people do not move to retirement homes or senior citizen communities
as they age. The vast majority actually age in place in single-family homes.
Housing studies show that the single-family home is not only the most common
form of housing for senior citizens, but it is also the type of housing most
often preferred by them. [Planning for and Aging Society, p. 15] However,
many elderly people on fixed incomes may find it difficult to stay in their
homes in the face of rising costs for utilities, maintenance and property taxes.
ADUs may allow some of these elderly homeowners to stay in their homes, even
on fixed incomes, where the extra income from an ADU helps them to offset some
of their living expenses.
ADUs Provide Homeowners with the Ability to Trade Rent Reductions for Needed
Services. Homeowners may also offer lower rents to tenants in exchange for
assistance in performing various household services. For some elderly homeowners,
being able to exchange rent reductions for needed services could be a deciding
factor enabling them to stay in their homes.
The ability to exchange reduced rents for services will also benefit many other
groups of homeowners, including young families, single parents, and handicapped
persons. For example, a mother with young children may rent an ADU to an elderly
couple and make an arrangement for reduced rent in exchange for regular babysitting.
Tenants, of course, would also benefit from service exchange arrangements by
having their rents reduced in return for performing various services.
For owner-occupiers who live alone, for the widowed, retired, or infirm,
or for young families with small children, the opportunity to
exchange services with tenants next door offers substitutes for
social supports that were provided by the extended family in earlier
Accessory Apartments in Single-Family Housing
ADUs Provide Increased Security and Companionship. Besides the financial
benefits, many homeowners will also benefit from the security and companionship
provided by having a tenant who lives close by. For an elderly person, concerns
about injuries while they are home alone and fears about rising neighborhood
crime rates may be greatly reduced just by the fact of having someone else living
under the sameroof. The presence of a tenant may also enhance security while
homeowners are out of town.
ADUs Can Help First-Time Buyers Qualify for Loans and Help Offset Mortgage
Payments. For a single individual or a young family buying their
first home, the presence of an ADU and its potential rental income may help
them to qualify for a larger mortgage loan than they otherwise might get. After
purchasing a home, the rental income from an ADU could help reduce the financial
burden of a high mortgage payment. Young families could rent out an ADU until
a time when their incomes have risen and they need more room. In this way ADUs
allow families the flexibility to adjust the way they use their homes to suit
changing life-cycle needs.
Moderately-Priced Rental Housing. Studies have shown that ADUs rent
for less than average market rent levels. Lower rents are possible primarily
because ADUs do not require the development of new land and are cheaper to build
than conventional rental units. [Accessory Units: An Increasing Source of
Affordable Housing, p. 5] Homeowners are also less likely to charge
market rents because of their interest in getting and keeping good tenants.
Lower rents for ADUs may make it easier for some tenants to save for a downpayment
on a home of their own. Rising rents for multifamily housing have been cited
as a major barrier to many prospective homebuyers who are having a more difficult
time saving enough to make the required down payment on a new home.
ADUs Provide Affordable Rental Housing in Single-Family Neighborhoods.
ADUs also offer housing opportunities in more desirable single-family neighborhoods
for some who might not otherwise be able to afford to live there. For many single
individuals, single parents, or others with modest incomes, the only other housing
option available may be apartment complexes. Living in an ADU would give these
households the opportunity to enjoy the amenities typically found in many single-family
neighborhoods, including more privacy, a quieter environment, and less traffic
ADUs Increase Housing Opportunities for Handicapped People. Handicapped
people often face limited opportunities for housing that can meet their special
needs. ADUs can provide many handicapped individuals with the opportunity to
live independently in their own home but close enough to others to provide needed
Regulatory Issues and Options
Accessory dwelling units do represent a controversial housing alternative in
many communities. Therefore, it is important to carefully assess the local issues
and options presented by ADUs. Ultimately, most communities will address ADUs
through the adoption of zoning ordinances designed to regulate the conditions
under which they will be allowed. However, there are several preliminary issues
that policy-makers may want to consider before deciding what zoning regulations
may be appropriate for ADUs. Among the more important questions to consider
- What are the community's housing goals and how will these affect the regulation
- What is the likely demand for ADUs in the community?
- What are the characteristics of the community's existing housing stock?
The answers to these questions will provide valuable information and insights
that can assist and guide policy-makers in deciding the best course for the
Community Goals: Balancing Neighborhood Concerns with the Need for Affordable
One of the first issues to consider is the community's housing goals. ADU regulations
are likely to vary depending on the goals the community chooses to implement.
The most common reasons cited for allowing ADUs are: (1) to expand the supply
of affordable housing for both owners and renters in the community; (2) to provide
a means for homeowners, particularly the elderly, to obtain extra income, security,
companionship, and services; (3) to make more efficient use of existing housing
stocks and infrastructure; and (4) to provide a mix of housing that responds
to changing family needs.
From the perspective of some homeowners, however, ADUs may be viewed as a potential
threat to the stability of single-family neighborhoods that should either not
be allowed or, at least, closely controlled to avoid any potential negative
impacts. For these homeowners, the most important goals may be to protect property
values,neighborhood stability, and to preserve the single-family character of
The challenge for policy-makers is to find the right balance between the community's
need for more affordable housing and the desire to preserve the quality of residential
neighborhoods. There are many opportunities for communities to be creative in
meeting this challenge.
The purpose of allowing ADUs is to:
- Provide homeowners with a means of obtaining, through tenants in either
the ADU or the principal unit, rental income, companionship, security, and
- Add affordable units to the existing housing.
- Make housing units available to moderate-income people who might otherwise
have difficulty finding homes within the (city/county).
- Develop housing units in single-family neighborhoods that are appropriate
for people at a variety of stages in the life cycle.
- Protect neighborhood stability, property values, and the single-family
residential appearance of the neighborhood by ensuring that ADUs
are installed under the conditions of this Ordinance.
Model Accessory Dwelling Unit Ordinance
Washington State Department of Community, Trade, and Economic Development
Opposition to accessory units usually arises from neighborhood concerns about
the perceived impacts of ADUs with respect to such issues as property values,
density, changes in neighborhood appearance, and increased parking and traffic
congestion. In response to these concerns, many communities have adopted regulations
designed to deal with such issues as the size of units, their exterior appearance,
off-street parking, and their concentration in neighborhoods. The general intent
of these types of regulations is to calm neighborhood fears by controlling the
number of conversions, minimizing neighborhood change, and upholding prevailing
ADU proponents point out the importance of reducing regulatory obstacles and
argue that, if controls are too restrictive, some homeowners will be unwilling
or unable to add an ADU. Such regulations might include undue cost-generating
requirements,overly-burdensome parking regulations, or restrictions on who will
be allowed to live in ADUs. Supporters also argue against cumbersome review
procedures, particularly those that may involve public hearings. They point
out that many homeowners,particularly the elderly, may be intimidated by and
unwilling to go through a lengthy public review process.
Need and Demand for ADUs - How Many Units Will be Built?
Another issue that bears some consideration before zoning regulations can be
adopted is the current need and demand for rental units in general and ADUs
in particular. As part of their growth management planning, many communities
in Washington are already required to conduct a housing needs assessment that
includes an inventory of existing housing stocks and an analysis of housing
needs. This type of information can also help policy-makers in evaluating zoning
alternatives for ADUs. For example, the existence of low rental vacancy rates
may suggest that there is a high potential demand for additional rental units,
including ADUs. High vacancy rates also serve to reduce the risk for homeowners
who want to install an ADU.
Although this information may be more difficult to collect, some estimate of
the number of existing accessory apartments in the community will also be useful
to policy-makers. The presence of many illegal units would be one indication
of the demand for this housing option. [Accessory Apartments in Single-Family
Another question that usually comes up in discussions of ADUs concerns the
number of units that are likely to be built. The answer to this question will
vary for each community and is related to such factors as current vacancy rates,
housing characteristics, and the restrictiveness of the community's zoning regulations.
Opponents often worry that legalizing ADUs will lead to a flood of applications
and conversions resulting in too many units. In response to these concerns,
some communities have adopted regulations that attempt to limit, either directly
or indirectly, the number of ADUs that can be installed in the community. By
all accounts, however, the experience of other communities that have legalized
ADUs seems to indicate that the actual number of conversions is likely to be
relatively low. One national survey involving 47 communities suggests that communities
with "favorable" zoning can expect to get approximately one ADU per
1,000 single family homes per year. [Accessory Units: An Increasing Source
of Affordable Housing, pp. 5-6]
Know Your Housing Stock
Policy-makers should also have some familiarity with the makeup and composition
of the community's existing housing stock, including any evidence of current
orprojected surplus space in single-family housing. Information on home and
household size will be available from census data on housing. Current census
statistics reveal that many people are living in homes that have surplus space.
A high percentage of homes with extra habitable space may be another indicator
of the potential for ADU conversions in the community.
Keys to Success
Achievable standards, fast track processing for units meeting standards,
and sensitivity to compatibility within existing neighborhoods
are all techniques to encourage second unit development.
Develop specific performance standards dealing with such issues as
minimum lot size, maximum unit size, parking standards, setback and
Limits on the maximum number of units within a neighborhood, requirements
for owner occupancy, and high parking requirements may be necessary
to ameliorate community concerns, but they may deter construction
of second units.
If second unit approvals can be made without a conditional use permit
or other action requiring public hearing, property owners will
find it less burdensome to add second units.
Financial or technical assistance can encourage second unit development
and improve their affordability.
Allow for the legalizing and upgrading of existing units so as to conform
with health and safety requirements. This can be encouraged
by establishing building code requirements to achieve minimum
health and safety requirements and by streamlining the conformance
Blueprint for Bay Area Housing
Association of Bay Area Governments, et al.
Also, are existing homes in the community of a type that are easily converted?
Split level, Cape Cod, and ranch style houses may be good candidates for conversion,
while many smaller bungalow style homes may not. Other home features that may
lendthemselves to adding an ADU include: detached garages, daylight basements,
two-story homes, larger homes, and alley access. The relative ease of conversion
of the predominant housing types in the community will also have an impact on
the potential for ADU conversions.
Again, information of this type can help policy-makers in evaluating the appropriateness
of proposed regulatory options.
The remaining sections contain a review of zoning provisions that have been
proposed and in many cases adopted to regulate ADU conversions in single-family
districts. Each section contains a discussion of the rationale for the regulation
together with sample ordinance provisions. For a comparison of ADU zoning regulations
adopted by a sample of 10 Washington cities, see Appendix II.
Zoning Regulations for ADUs - Issues and Options
Most zoning ordinances contain some definition of the term "accessory
dwelling unit," which may also be called an "accessory apartment,"
"accessory living unit," "accessory cottage," or a similar
term. A good definition is important to provide a common understanding of the
term and may also be useful to establish basic requirements and limitations.
ADUs are most commonly defined as a self-contained living unit created within
or detached from a single-family dwelling. Many ordinances also highlight the
existence of separate cooking, sleeping, and sanitation facilities as distinguishing
An accessory dwelling unit (ADU) is a habitable living unit added to, created
within, or detached from a single-family dwelling that provides basic
requirements for living, sleeping, eating, cooking, and sanitation.
[Sec. 19.04.0607(B), Mercer Island Municipal Code]
Note that the above definition includes units that are either "added to,
created within, or detached from" a single-family dwelling, which indicates
that both attached and detached units are allowed. Some communities, however,
have decided to limit ADUs only to units attached to the main residence. ADUs
in these communities may be defined in a way that excludes detached units.
"Accessory dwelling unit" means a subordinate dwelling unit incorporated
within a single family structure. Accessory units may not be subdivided
or otherwise segregated in ownership from the primary residence structure.
[Sec. 20.20.120(A)(1), Bellevue City Code]
The term "accessory" in "accessory dwelling unit" denotes
a use that, under zoning regulations, is commonly understood to be one that
is subordinate in size, location, and function to the principal unit. Communities
that wish to underscore this point may also choose to highlight the subordinate
or secondary nature of ADUs in their definition.
Accessory Dwelling Unit: A second subordinate dwelling unit added to or created
within a single-family dwelling ... with a provision for independent cooking,
living, sanitation, and sleeping. [Sec. 13.06.010(1)(c), Tacoma Municipal
Review and Approval Procedures
ADUs are typically regulated either as a permitted use, with an administrative
review, or as a conditional use, subject to a public hearing requirement.
ADUs that are regulated as a permitted use are usually allowed "as-of-right,"
if all applicable zoning and building code requirements are met. The approval
process normally involves some type of administrative review and an inspection
of the premises to ensure compliance with ordinance requirements. Under an administrative
review process, the ADU permit is issued if the applicant meets the development
standards without the necessity of a public hearing. The permitted use approach
offers the advantage of administrative simplicity and is less intimidating for
homeowners who want to install an ADU but who may be reluctant to go through
a public hearing review.
The installation of an ADU in new and existing single-family dwellings (hereinafter
principal units) shall be allowed in single-family zones subject to specific
development, design, and owner-occupancy standards. [CTED (Dept. of Commerce) Model Accessory
Dwelling Unit Ordinance]
Conditional use procedures are usually more rigorous and often add a neighborhood
notice and public hearing requirement to the review process. Conditional use
permit procedures have the advantage of providing for a case-by-case review
of ADU applications, which may allow a more tailored response to problems.
ADU proponents argue that requirements for conditional use permits and public
hearings are too cumbersome and intimidating and will present too much of a
barrier to those who might otherwise benefit from this housing alternative.
They argue that requirement may actually encourage the installation of more
As an alternative procedure, some communities provide for an exemption from
the public hearing requirement if, after notification of the property owners
within a certain distance from the applicants property, the planning department
receives no requests for a hearing. This approach has the advantage of avoiding
unnecessary hearing expenses in cases where neighborhood residents are more
accepting of ADUs. It also spares homeowners from the burden of having to comply
with a significant regulatory hurdle. [Model Zoning, p. 4]
Even when no public hearing is required, some communities require that a notice
be sent to residents within a certain distance of the proposed ADU, either before
approval to allow residents an opportunity to comment on the permit, or after
the approval has been issued, to notify them about the ADU and the requirements
of the ordinance. A notice to neighborhood residents lets them know what to
expect and what their enforcement options are if problems arise. In some communities,
the inclusion of public notice provisions may be necessary to satisfy the concerns
After approval, the Director shall provide notice of the registration of
the accessory unit to owners of property within 200' of the registered
site. The notice shall state that the unit complies with the standards
of this section, shall describe the requirements for maintaining the
unit, and shall explain how to obtain general information and how to
request inspections. [Bellevue Ordinance No. 4498]
The current trend among Washington cities that have recently adopted ADU ordinances
has been toward a permitted use approach that allows ADUs in single-family zones
subject to various development standards designed to preserve neighborhood character
A common apprehension of opponents is that ADUs may harm neighborhood character
if they are not properly maintained by owners and/or renters. Opponents also
express concern that too many ADUs may be created if individual speculators
can purchase or develop multiple homes with ADUs. In response, many communities
require that the homeowner must occupy either the principal or the accessory
unit. The expectation is that homeowners will be more likely to maintain the
property if they also live there. Also, by limiting ADUs to owner-occupied homes,
individual speculators are effectively prevented from building multiple units.
The property owner, which shall include title holders and contract purchasers,
must occupy either the principal unit or the ADU as their permanent residence,
but not both, . . . and at no time receive rent for the owner-occupied
unit. [CTED (Dept. of Commerce) Model Accessory Dwelling Unit Ordinance]
'Owner occupancy' means a property owner, as reflected in title records,
makes his or her legal residence at the site, as evidenced by voter
registration, vehicle registration, or similar means .... [Ch.
20.20.120(A)(3), Bellevue Municipal Code]
Owner-occupancy requirements are also thought to have the added benefit of
ensuring better tenant management, since resident owners will be more likely
to enforce appropriate behavior standards.
Where the community does not intend to require that homeowners must occupy
the principal unit, it may be useful to clarify in the ordinance that the they
can live in either unit. Many homeowners, particular the elderly, who no longer
need the space or who wish to avoid the burden of caring for the larger unit,
may want the option of living in the smaller unit. [Accessory Apartments
- Using Surplus Space in Single-Family Houses, p. 6]
Communities that adopt owner-occupancy restrictions may also want to include
a provision that exempts temporary absences to allow some flexibility for homeowners
while still requiring that the home be maintained as their principal residence.
One (1) of the dwelling units in the structure shall be occupied by one or
more owners of the property as the owner's(s') permanent and principal
residence; provided that the Director may waive this requirement for
temporary absences of less than one (1) year, where the accessory unit
has been a permitted use for at least two (2) years and the owner submits
proof of absence from the Puget Sound region. [Sec. 23.44.025(A)(2),
Seattle Municipal Code]
To ensure compliance, some communities require that homeowners sign an affidavit
affirming that they will occupy either the primary or accessory residence.
Affidavit. The property owner shall sign an affidavit before a notary public
affirming that the owner occupies either the main building or the ADU
.... [Sec. 13.06.196(B)(3), Tacoma Municipal Code]
For added insurance that owner-occupancy requirements will continue to be met,
some communities provide for termination of an ADU permit upon the sale of the
property and require new owners to re-register.
Upon sale of the property, a new owner shall be required to sign a new affidavit
and to register the ADU, paying a reauthorization fee of $100 .... [Sec.13.06.196(B)(2),
Tacoma Municipal Code]
Some ordinances require that the owner occupancy requirement be recorded as
a deed restriction to put prospective buyers on notice of the prohibition against
renting out both units. Whenever there is a transfer of ownership of the property,
the title search turns up the document noting the regulation. See "Recording
Requirements" on page 49.
In addition to the requirement that homes with ADUs must be owner-occupied,
some communities also require that owners must have lived in their homes for
a certain number of years before they can install an ADU. See "Length of
Residence" on page 48.
ADU/Principal Residence Size Regulations
ADU ordinances often contain provisions regulating the size of ADUs
and/or the principal unit. Size limits for ADUs are expressed either in absolute
terms or some percentage of the principal unit (usually in the range of 20%
to 40%). Size regulations may specify minimum and/or maximum sizes for the ADU
or the primary residence. Some ordinances also regulate size by specifying a
maximum number of bedrooms (e.g., two bedrooms) allowed in an ADU.
In no case shall an ADU be more than 40 percent of the building's total floor
area, nor more than 800 square feet, nor less than 300 square feet, nor
have more than 2 bedrooms, unless in the opinion of the (building official),
a greater or lesser amount of floor area is warranted by the circumstances
of the particular building. [CTED (Dept. of Commerce) Model Accessory Dwelling Unit
Size limitations serve several purposes. Most often they are designed to ensure
that ADUs remain subordinate in size to the primary residence (percentage based
limits, in particular, are designed to ensure that an ADU remains subordinate
regardless of home size). They are also intended to control neighborhood density,
the assumption being that controls on the size of ADUs will also tend to limit
the number of tenants who can live in an ADU. Size limits are also aimed at
minimizing visual impacts of additions or alterations to the residence.
The ADU, excluding any garage area and other non-living areas such as workshops
or greenhouses, shall not exceed 33 percent of the total square footage
of the main building and the ADU combined after modification. The ADU
shall not contain less than 300 square feet or more than 800 square feet.
[Tacoma Ordinance No. 25624]
Note that the size limitations in the above provision, which are relatively
permissive, effectively require a minimum home size of 900 square feet in order
to install a minimum-sized 300 square foot ADU. ADU proponents caution that
a size limit based on a ratio between the primary unit and the ADU should be
small enough to keep ADUs subordinate to the primary unit, but not so small
as to require a large house to establish a viable ADU. Since house size and
income are often related, aminimum home size requirement that is too restrictive
could eliminate some homeowners who might benefit most from the opportunity
to install an ADU.
If minimum/maximum size requirements are adopted, it may be helpful to give
some discretion to the reviewing agency to modify requirements in cases where
strict adherence would be impractical or uneconomical. For example, many two-story
homes may be most economically converted by installing an ADU on the bottom
floor which may take up half or nearly half of the entire space available. Or
an ordinance may provide exemptions for the use of basement or attic space that
are more than the specified maximums.
The accessory dwelling unit shall contain not less than 300 square feet and
not more than 800 square feet, excluding any related garage area; provided,
if the accessory unit is completely located on a single floor, the Director
may allow increased size in order to efficiently use all floor area,
so long as all other standards set forth in this section are met.
[Bellevue Ordinance No. 4498]
Some ordinances do not contain specific size requirements but rely instead
on applicable zoning, health, housing and building codes that regulate general
height, set-back and lot coverage, and establish minimum space requirements
Attached Or Detached?
One question that the community must answer is whether to allow detached ADUs.
Some cities have limited ADUs to attached units to reduce the visual impact
and to preserve the single-family character of neighborhoods. When made a part
of the main house an attached unit is kept as a subordinate use and does not
give the impression of two separate houses on a single-family lot. Where average
lot sizes are very small throughout the community, this may be an appropriate
Location: Accessory dwelling units shall not be permitted in structures detached
from the primary residence, including but not limited to guest cottages, detached
garages, or workshops. [Bellevue Ordinance No. 4498]
Detached units are less frequently allowed in zoning codes and are generally
more expensive to build than an attached unit. While they are more visible as
detached units, where they are permitted, they are usually required to be located
in the rear yard area to minimize the visual impact of two separate residences.
[Accessory Units: An Increasing Sources of Affordable Housing,
p. 5] In many cases, a detached residence may provide a better living arrangement
for those who want an ADU but who do not wish to have someone else living in
the same physical structure. Even on relatively small lots, a unit may be successfully
installed in a previously existing detached garage or similar structure.
The ADU may be attached to, or detached from, the principal unit. [CTED (Dept. of Commerce)
Model Accessory Dwelling Unit Ordinance]
Some communities allow detached ADUs only on larger lots.
7.a. Accessory dwelling units: ...
(2)Only in the same building as the principal residence unless
the lot is at least 10,000 square feet in area and the allowable density
of the zone is not exceeded. [Sec. 21A.08.030(B), King County Zoning
ADU Occupant Restrictions
Some ordinances, particularly those adopted 10 or more years ago, contain restrictions
on who may live in an ADU. These ordinances typically provide that tenants must
be a certain minimum age, usually 60 or 65, and/or that tenants be related to
the owner. Ordinances may also specify that tenants be limited to employees
of the homeowner or have some other special relationship (e.g., providing in-home
care or assistance) to the homeowner. Typically, these types of restrictions
are intended to allow residents to install an ADU for the limited purpose of
providing in-home care to aging parents while maintaining separate living areas.
Ordinance restrictions that limit the age of tenants or that require that the
tenant be related to the homeowner are intended to preserve the "family
character" of neighborhoods and to keep the number of conversions low,
while still allowing them for the purpose of dealing with special family needs.
Occupancy of the accessory or principal unit is limited to family members
related by blood, marriage, or adoption, or persons providing nursing
or domiciliary care of assistance to the owner in exchange for lodging.
[Sec. 11.19.3210(B)(3), Spokane Municipal Code]
ADU proponents argue that restrictions based on the age or familial status
of tenants may discourage some homeowners from installing an ADU because of
the risk of losing their investment in the event that their tenant moves away
or dies. Because of the tenant restrictions, homeowners may have difficulty
finding another renter who meets the ordinance's requirements. [Accessory
Apartments - Using Surplus Space in Single-Family Houses, p. 13]
Restrictions on the age of tenants and their relationship to homeowners may
also be difficult to enforce. When relatives die or move away, homeowners will
be left with an empty and unusable apartment and may be tempted to fill the
vacancy in violation of the ordinance. Without adopting a cumbersome enforcement
procedure and in the absence of neighbor complaints, it may be difficult for
communities to keep tabs on the status of ADU tenants.
As more communities have come to view ADUs as an important means of providing
affordable housing alternatives, these types of restrictions, which limit opportunities
to install ADUs to relatively few homeowners, have become less common. Few of
the ordinances reviewed for this report contained restrictions of this type.
Number of Occupants
Limits on the numbers of occupants in homes with ADUs are designed to control
overcrowding in homes with ADUs and increased neighborhood density, as well
as related parking and traffic impacts.
Some communities limit the aggregate number of persons that may occupy both
the ADU and primary unit to the number allowed in the house without the rental
unit. [Accessory Apartments - Using Surplus Space in Single-Family Houses,
p. 8] In theory, under this restriction, the density, parking, and traffic impacts
resulting from ADU conversions should be no greater than those from a single-family
structure without an ADU. Ordinances may also refer to provisions in the zoning
code defining "family" that generally contain limitations on the numbers
of related and/or unrelated persons who can live in a single residence.
The total number of occupants in both the primary residence and the accessory
dwelling unit combined may not exceed the maximum number established
by the definition of family in Section 20.50.020. [Sec. 20.20.120(B)(2),
Bellevue Land Use Code]
Any number of related persons may occupy each unit in a single-family
residence with an accessory dwelling unit provided that if unrelated
persons occupy either unit, the total number of persons occupying both
units together may not exceed eight (8). [Sec. 23.44.025(A)(3),
Seattle Municipal Code]
Some ordinances place specific limitations on the occupancy of ADUs based on
the size of the unit. This type of occupancy limitation is more sensitive to
individual variations in the size of ADUs.
Occupancy. Occupancy shall be limited to the following: No more than two
persons in a unit of 300-400 square feet, no more than three persons
in a unit ranging from 401-600 square feet, and no more than four persons
in a unit ranging from 601-800 square feet. [Sec. 13.06.196(C)(2),
Tacoma Municipal Code]
The potential for parking problems generated by the installation of ADUs is
one of the most common concerns expressed by residents. Neighborhood groups
are generally opposed to any increases in on-street parking, particularly in
areas where competition for existing parking is already a problem, or in neighborhoods
where prevailing aesthetic standards make on-street parking less acceptable.
Many communities have addressed this issue by requiring a certain number of
off-street parking spaces for homes with ADUs. Off-street parking requirements
typically range from one to one and one-half off-street spaces per ADU. [Accessory
Apartments -Using Surplus Space in Single-Family Houses, p. 14].
Whether parking will become a problem depends to a great extent on current
neighborhood standards and the perceptions of residents about existing parking
problems. In some neighborhoods, on-street parking is a common practice and
may therefore be more acceptable, while in others, off-street parking in garages
is the more common rule. Varying neighborhood standards may suggest the need
for a response that is more tailored (e.g., based on performance standards rather
than specific parking requirements) to the particular needs of each neighborhood.
[Accessory Apartments in Single-Family Housing, p. 172]
Once the community decides to require off-street parking for ADUs, the next
question is where such spaces will be allowed. One concern expressed by neighborhood
groups is that additional off-street parking be provided in a way that will
not detract from the neighborhood's low-density, single-family character. Solutions
might include restrictions on parking in front yard areas or landscaping requirements
to limit visual impacts.
Parking. One off-street parking space shall be required for the ADU, in
addition to the off-street parking required for the main building....Such
parking must be provided in the rear of the lot where adequate access
is available. Adequate access shall be defined as a dedicated street
or alley with a minimum gravel surface. [Tacoma Ordinance No. 25624]
One off-street parking space, in addition to that which is required by the
Ordinance for the underlying zone, shall be provided or as many spaces
deemed necessary by the (building official) to accommodate the actual
number of vehicles used by occupants of both the primary dwelling and
the ADU. Parking spaces include garages, carports, or off-street areas
reserved for vehicles. [CTED (Dept. of Commerce) Model Accessory Dwelling Unit Ordinance]
Some communities allow homeowners to use tandem parking (one car behind the
other) as a less costly alternative for satisfying requirements for off-street
A minimum of two (2) off-street parking spaces shall be provided, which
spaces may be in tandem. The Director may waive the requirement for one
(1) or both of the spaces if topography or existing structures makes
provision of one (1) or both of the parking spaces unduly burdensome
and adequate parking capacity exists. [Sec. 23.44.025(A)(7), Seattle
Proponents point out that in many instances single-family homes without ADUs
could generate just as much traffic and demand for parking as a home with an
ADU, particularly in homes with teenage children. They point out that ADUs are
often in the homes of "empty nesters," single parents, and single
residents, who tend to have fewer cars. Meeting requirements for additional
parking spaces could be an expensive proposition for some homeowners and may
discourage them from installing an ADU.
Provisions that govern the design and appearance of homes with ADUs are intended
primarily to preserve the visual and single-family character of neighborhoods.
Many ordinances contain conditions limiting certain exterior modifications of
homes with ADUs. These may include limitations on additions that increase the
size of the home, restrictions on the location of entrances and exterior stairs,
and other design guidelines. [Accessory Apartments - Using Surplus Space
in Single-Family Houses, p. 16]
The creation of an accessory living unit is subject to the following requirements:
... (5) Any additions to an existing structure for the purpose of the
accessory unit do not increase the square footage of the structure by more
than ten percent. [Sec. 11.19.3210(B)(5), Spokane Municipal Code]
While some ordinances contain specific square foot limits on expansions, others
simply rely on existing setback and lot coverage requirements to control the
size of additions.
Any additions to an existing building shall not exceed the allowable lot
coverage or encroach into the existing setbacks. [CTED (Dept. of Commerce) Model Accessory
Dwelling Unit Ordinance]
Some communities prohibit any increase in home size to accommodate an ADU.
Restrictions of this type are intended to minimize any changes to the exterior
appearance of homes with ADUs.
Single-family conversions may only be installed within existing structures,
whether primary or accessory structures, subject to the following conditions:
4. No additions to the existing floor area are necessary as a part of
the conversion. [Sec. 18.42.010(D), Tumwater Municipal Code]
Proponents point out that restrictions on the size of additions may not be
either necessary or effective. The high cost of remodeling may be just as effective
at limiting large new additions to accommodate ADUs. Additionally, it may be
easy forhomeowners to avoid this type of restriction simply by adding space
at one time to be later converted into an ADU. [Model Zoning, p. 15]
In an attempt to discourage homeowners from circumventing size limitations,
some communities prohibit the installation of ADUs in homes that have recently
added on space. This type of restriction also seeks to encourage the use of
existing surplus space, rather than new additions that increase density, to
Single-family conversions may only be installed within existing structures,
whether primary or accessory structures, subject to the following conditions:
3. Where no additional floor area has been added in the preceding two
years; and [Sec. 18.42.010(D), Tumwater Municipal Code]
Many of the appearance and design standards applied to homes with ADUs are
concerned with those portions of the home that can be seen from the street.
One of the most common provisions prohibits the creation of additional front
entrances. Communities typically require that entrances to ADUs be located on
either the rear or side of the home.
Only one (1) entrance may be located on each front or street side of the
residence ... [Sec. 23.44.025(A)(6), Seattle Municipal Code]
The primary entrance to the ADU shall be located in such a manner as to
be unobtrusive from the same view of the building which encompasses
the entrance to the principal unit. [CTED (Dept. of Commerce) Model Accessory Dwelling
The installation and/or location of exterior stairs is also likely to be restricted
to rear or side yard locations or prohibited altogether.
Many communities also include a stipulation in their ordinance that any modifications
to the exterior of the home should conform to the original design characteristics
and style of the home.
When reviewing a conditional use request for an accessory apartment, the
hearing examiner shall consider the following guidelines: . . . 3. The
design of the accessory apartment is incorporated into the primary unit's
design with matching materials, colors, window style and roof design.
[Sec. 17.16.030(G)(3), Gig Harbor Municipal Code]
Design. An ADU shall be designed to maintain the architectural design,
style, appearance and character of the main building as a single-family
residence. If an ADU extends beyond the current footprint or existing
heightof the main building, such an addition must be consistent with
the existing facade, roof pitch, siding and windows. [Tacoma Ordinance
Some ordinances simply say that any changes to the exterior of the home should
not alter the "single-family character" of the neighborhood.
The ADU shall be designed so that, to the degree reasonably feasible, the
appearance of the building remains that of a single-family residence.
[CTED (Dept. of Commerce) Model Accessory Dwelling Unit Ordinance]
This type of provision allows the reviewing agency some discretion and flexibility
in applying design guidelines. However, unless "single-family appearance"
or "character" are defined in some way, it may be difficult for a
community to deny a permit application.
What to do with existing illegal ADUs? Illegal units may be common in communities
where there is excess demand for rental apartments, where zoning laws prohibit
or tightly restrict ADUs, and where enforcement procedures are slow and/or ineffective.
[Accessory Apartments in Single-Family Housing, p. 187]
So, depending on the circumstances, you may already have a substantial number
of ADUs in your community. Some may predate the adoption of your city's zoning
code and may therefore be classified as legal nonconforming units. Any ADUs
built after the adoption of zoning codes prohibiting them would, of course,
be classified as illegal units. Building and planning officials often have some
idea of the number of illegal units in the community.
Safety is usually the most important concern of communities with illegal ADUs.
When an ordinance allowing ADUs is adopted, many communities provide incentives
for the owners of illegal units to legalize them and to bring them up to minimum
fire and life safety requirements.
One option for encouraging legalization of existing illegal units is to waive
any applicable fines for homeowners who apply for a permit within a certain
period (e.g., six months) following adoption of the ordinance. Allowing a grace
period for homeowners to modify illegal units that do not meet minimum health
and safety standards may also be a useful incentive.
That portion of a single family residence which meets the definition of accessory
dwelling unit which was in existence prior to January 17, 1995, may continue
in existence provided the following requirements are met:
- An application for an accessory dwelling unit is submitted within eighteen
(18) months of January 17, 1995.
- The unit complies with the minimum requirements of the Uniform Building
Code, Section 1208....
[Sec. 19.04.0607(D), Mercer Island Municipal Code]
Owners of illegal units who apply for a permit within the grace period may
also be given some leeway on minor violations of ADU size, lot size, setback,
parking, andother requirements where full compliance would be impractical. [Model
Zoning, p. 29]
The Director may waive the one thousand (1,000) square feet limitation
where exceeded in an accessory dwelling unit existing on January 1,
1993, if an application to legalize the accessory dwelling unit is
filed within eighteen (18) months of the effective date of the ordinance
codified in this section and if the Director finds that reduction of
the floor area would be impractical. [Sec. 23.44.025(A)(5), Seattle
Imposing a stiff penalty on the owners of illegal units discovered after the
grace period has run out may also serve as an effective incentive for owners
to legalize their unauthorized units.
Legalization of Nonconforming ADUs. Nonconforming ADUs existing prior to
the enactment of these requirements may be found to be legal if the property
owner applies for an ADU permit prior to December 31, 1995, and brings
the unit up to Minimum Housing Code standards. After January 1, 1996,
owners of illegal ADUs shall be guilty of a misdemeanor and, upon conviction
thereof, subject to a fine not to exceed $1,000, including all statutory
costs, assessments, and fees, plus $75 per day after notice of the violation
has been made. All owners of illegal ADUs shall also be required to either
legalize the unit or remove it. [Sec. 13.06.196(C)(11), Tacoma Municipal
Experience in other jurisdictions indicates that cities may expect only
limited success in getting owners of illegal units to come forward
and register them even when offered amnesty. Owners of illegal
conversions may prefer to keep their accessory apartments secret
in order to avoid paying property taxes on them. A more significant
motivation may be the desire to avoid income taxes. Even when
zoning is not a constraint, property owners may choose to convert
without a valid building permit in order to avoid the costs of
compliance with building codes.
Accessory Apartments in Single-Family Housing
Minimum Lot Size
Some communities restrict ADUs to lots that are over a certain minimum size.
The purpose of this type of restriction is to control density and, indirectly,
to limit the number of conversions.
Proponents point out that minimum and maximum ADU size requirements along with
existing lot coverage, setbacks, and other regulations are sufficient to control
density. They argue that minimum lot size requirements may prevent many older
homeowners and others with homes on small lots from securing the benefits of
an ADU. (Hare, Model Zoning, p. 25)
None of the Washington State ordinances reviewed for this report contained
a minimum lot size requirement for homes with attached ADUs.
Some communities have adopted a minimum lot size requirement for detached ADUs.
7.a. Accessory dwelling units: ...
(2) Only in the same building as the principal residence unless the lot
is at least 10,000 square feet in area and the allowable density of
the zone is not exceeded.... [Sec. 21A.08.030(B), King County Zoning
Density controls place a limit on the total number of homes within a particular
area (e.g., city blocks, census tracts, etc.) that can have ADUs. They are intended
to prevent traffic, parking, and other density-related impacts that may result
from an overconcentration of homes with ADUs. They are also intended to ensure
an even distribution of ADUs throughout the community. Such requirements may
limit the number of homes with ADUs that may be located within a certain distance
of one another, or they may place a cap on the total number of ADUs that may
be installed on a particular block without regard to proximity to other ADUs.
Density controls may serve as a useful reassurance for residents who are concerned
about the possibility of numerous new conversions appearing in single-family
neighborhoods. Since typical conversion rates are usually quite low, such restrictions
may not actually prevent many conversions. Density controls can always be reviewed
and possibly lifted at a later date after the community has gained more experience
with actual conversion rates. [Model Zoning, p. 24]
If ... applications are filed for accessory dwelling units which would cause
the concentration of single-family structures with new accessory dwelling
units to exceed twenty percent (20%) of all single-family structures
in single-family zones in any one census tract or in an area formed by
a circle with a radius of one thousand feet (1,000') form the point at
which three (3) or more census tracts meet, no further applications may
be accepted for accessory dwelling units in such census tract or area.
The Master Use Permit process set forth in Chapter 23.76 shall be followed
to authorize these uses. [Sec. 23.44.025, Seattle Municipal Code]
On the downside, dispersion requirements may be vulnerable to charges of inequity
where homeowners who want to install an ADU are prevented from doing so simply
because one or two other homeowners on the same block or within a certain distance,
have already done so. This may be particularly troublesome in cases where the
existing units were formerly illegal units that have recently been legalized.
Dispersion requirements may also discourage the owners of illegal units from
legalizing them and encourage the creation of new illegal units in areas that
have already reached their limit.
Age of Home
Some communities have adopted restrictions on ADU conversions based on the
age of the home. Ordinances that restrict the ADU conversions to homes that
are over a certain age (e.g., three years) effectively prohibit ADUs in new
construction. Regulations of this type are intended to limit the number of conversions
and to prevent developers from constructing and marketing new homes with accessory
apartments in single-family zones. Such regulations are also intended to prevent
new construction designed specifically for conversion at a later time.
One accessory dwelling unit is permitted as subordinate to an existing single-family
"Existing single-family dwelling" means that permits for construction
of the principal dwelling were finaled (occupancy approved) at least
three years prior to application for accessory dwelling unit. [Secs.
20.20.120(B) and (A)(2), Bellevue Land Use Code]
Supporters of restrictions based on the age of homes assert that the goal should
be to promote the recycling and better use of existing housing rather than to
encourage the development of "duplexes" in single-family neighborhoods.
ADU proponents question the need for restrictions on ADUs in newly constructed
homes. They argue that this type of restriction denies homeowners flexibility
in the use of their homes to allow for changes in family size, economic status,
or other life cycle changes. They also point out that ADUs can be more easily
included in new construction with designs that more effectively address exterior
appearance and parking issues. Many communities do allow ADUs in new as well
as existing homes.
An ADU may be developed in either an existing or a new residence. [CTED (Dept. of Commerce)
Accessory Dwelling Unit Ordinance]
It is not clear that allowing ADUs in new construction will result in waves
of ADU installations. Where there is concern over the potential numbers of ADUs,
sunset provisions or reviews that are triggered after a certain number conversions
may also provide reassurance to neighborhood groups, without restricting the
ability of young homebuyers or others who may benefit from the opportunity to
install an ADU in a newly purchased home. [Accessory Units: State of the
Art - Summary of Experience, p. 23]
Length of Residence
Some ordinances limit ADU conversions to situations where the homeowner has
lived in the house for a certain number of years (e.g., three years). These
regulations are intended to prohibit conversions at the time of purchase and
for a period of time after the purchase of both new and existing homes. Restrictions
based on length of residence are also designed to prevent homebuyers from purchasing
a home with the specific intent of installing an ADU. Such restrictions are
usually based on concerns that legalization will result in large numbers of
new ADU conversions.
... no application shall be considered for an accessory dwelling unit, unless
the applicant has owned and resided at the subject site for a period
of not less than two years prior to the application. [Sec. 20.21.010
Edmonds Municipal Code]
ADU proponents argue that regulations of this type effectively remove the opportunity
for first-time buyers to use the rental income from an ADU to help in qualifying
for a mortgage loan and to offset a portion of their house payment.
Only one of the Washington ordinances reviewed for this report contained restrictions
based on the length of homeowner residence.
To ensure continued compliance with owner-occupancy and other ordinance requirements
by current, as well as by any subsequent owners, many communities require that
either a deed restriction, covenant, or similar instrument be filed and recorded
by the homeowner.
Deed restrictions run with the land and put prospective buyers on notice with
respect to the requirements and limitations of the ordinance and, in some cases,
inform them of the steps they must take to apply for ADU permits. Whenever there
is a transfer of ownership of the property, the title search turns up the document
noting the regulations.
The registration form or other forms as required by the (building official)
shall be filed as a deed restriction with the (county) Department of
Records and Elections to indicate the presence of the ADU, the requirement
of owner-occupancy, and other standards for maintaining the unit as described
above. [CTED (Dept. of Commerce) Model Accessory Dwelling Unit Ordinance]
Some ordinances require homeowners to sign and file an agreement binding them
to comply with all of the ADU ordinance provisions. The agreement may also provide
an additional avenue for enforcement of the ordinance's requirements.
The applicant shall provide a covenant in a form acceptable to the City Attorney
and suitable for recording with the County Auditor, providing notice
to future owners or long term lessors of the subject lot that the existence
of the accessory dwelling unit is predicated upon the occupancy of either
the accessory dwelling unit or the principal dwelling by the person to whom
the accessory dwelling unit permit has been issued. The covenant shall
also require any owner of the property to notify a prospective buyer of the
limitations of this Section and to provide for the removal of improvements added
to convert the premises to an accessory dwelling unit and the restoration
of the site to a single family dwelling in the event that any condition
of approval is violated. [Sec. 39.020(D)(13), Everett Zoning Code]
Utility Service Requirements
ADU ordinances sometimes require applicants to get a permit approval affirming
the adequacy of existing water and sewer service capacity. This may be important
in cases where the principal and accessory units combined have more bedrooms
than the original home or in rural areas where older septic systems may be near
capacity. In cases where the existing capacity is inadequate, the ordinance
may require proof that provisions will be made for adding capacity. [Accessory
Units: State of the Art - Model Zoning, p. 30]
Certification by the (city/county) Health Department that the water supply
and sewage disposal facilities are adequate for the projected number
of residents must be provided to the building official. [CTED (Dept. of Commerce) Model
Accessory Dwelling Unit Ordinance]
Proponents point out that ADUs in most cases will not increase the number of
people living in a house beyond the number for which it was originally designed
and should not therefore cause any problems with respect to increased burdens
on water and sewer systems. [Accessory Apartments - Using Surplus Space in
Single-Family Houses, p. 15] Instead of requiring new infrastructure,
ADUs may actually result in more efficient use of existing underutilized service
Some ordinances also prohibit the principal and accessory units from having
separate utility meters. Requiring service through single water and electrical
meters is intended to reinforce owner-occupancy requirements and to avoid the
"duplex look" of separate electrical meters.
An accessory apartment must be connected to the utilities (except telephone
and television) of the dwelling unit and may not have separate services.
[Sec. 23.70.030(10), Richland Municipal Code]
Provisions to Encourage Barrier-Free ADUs
ADUs increase housing opportunities for handicapped persons by allowing them
to live independently in a separate dwelling but close to any needed support.
The community may want to consider including provisions to encourage the installation
of barrier-free ADUs. One option would be to relax certain requirements where
doing so would facilitate the installation of a barrier-free unit. It may also
be helpful to add a statement in the ADU ordinance declaring the community's
intention to increase affordable housing opportunities for the handicapped.
[Accessory Apartments - Using Surplus Space in Single-Family Houses,
In order to encourage the development of housing units for disabled and handicapped
individuals, and persons with limited mobility, the director may allow
reasonable deviation from the prescribed conditions where necessary to
install features that facilitate access and mobility of disabled persons. Such
facilities are in conformance with Washington State regulations for barrier-free
facilities. [Sec. 11.19.3210(B)(13), Spokane Municipal Code]
In order to encourage the development of housing units for people with
disabilities, the (building official) may allow reasonable deviation
from the stated requirements to install features that facilitate accessibility.
Such facilities shall be in conformance with the UBC. [CTED (Dept. of Commerce) Model
Accessory Dwelling Unit Ordinance]
Maximum Number of ADUs per Lot
Most ordinances impose a limit of one ADU per single-family lot, particularly
in urban areas that may have smaller average lot sizes. This restriction is
intended to minimize increases in neighborhood density resulting from ADU conversions.
There shall be no more than one single-family conversion per lot. [Sec.
18.42.010(A), Tumwater Municipal Code]
Such limits may not be necessary or appropriate in some areas such as agricultural
zones where multiple accessory housing units may be provided on large lots (e.g.,
housing for farm workers).
Only one ADU may be created per residence in single-family zones. Multiple
detached ADUs may be created in (agricultural) zones, if one of the occupants
of each unit is employed by the property owner. [CTED (Dept. of Commerce) Model Accessory Dwelling
For most homeowners in single-family zones, the potential for adding more than
a single ADU is not great in any event, in view of space requirements and the
ADUs with Home Occupations
It may also be useful to consider what, if any, provisions there should be
to regulate home occupations (e.g., bed and breakfast, home businesses, day
care, etc.) in homes with ADUs. One option would be to prohibit all or certain
types of home occupations in homes with ADUs.
A property may not have both an accessory dwelling unit and a home occupation
as defined by this Ordinance. [Sec. 20.118.030(B)(8), Walla Walla Zoning
No home profession, family day care home, or mini day care facility may
be undertaken in either the principal or the accessory unit. [Sec.
11.19.3210(B)(8), Spokane Municipal Code]
Another option would be to allow home occupations in only one of the units,
either the primary unit or the ADU, but not both. Many communities have already
adopted regulations that are designed to control the impacts of home occupations.
These regulations may be sufficient to control any impacts from residences that
have both an ADU and a home business.
Home Occupations. Home occupations shall be allowed, subject to existing
regulations, in either the ADU of the main building, but not both.
[Sec. 13.06.196(C)(9), Tacoma Municipal Code]
As an additional safeguard, the ordinance could include a provision requiring
a review on a case-by-case basis of the cumulative impacts of a home occupation
with an ADU, particularly with respect to parking and traffic. The reviewing
agency may be provided with the discretion to modify ADU conditions or deny
a permit where the cumulative impacts are deemed to be excessive. [Accessory
Units: State of the Art -Model Zoning, p. 23]
Periodic Permit Renewal
Some ordinances require periodic renewal of ADU permits to allow closer monitoring
of ADUs over time and to ensure that any zoning requirements continue to be
met. This type of requirement can serve to allay the fears of neighborhood groups
concerned about enforcement of ordinance conditions for the period after the
permit has been issued. Periodic renewal of ADU permits also requires more planning
department resources for enforcement.
The owner of a single family dwelling with an accessory dwelling unit shall
file an Owner's Certificate of Occupancy in a form acceptable to the
City Attorney no later than April 1st of each year. [Sec. 39.020(D)(10),
Everett Zoning Code]
Proponents argue that, where they are adopted, reapproval procedures should
be routine unless conditions are no longer being met. A less onerous requirement
from the perspective of the homeowner would be to waive permit renewals unless
neighbors specifically complain and request a hearing. Another alternative would
be to require renewal at longer intervals (e.g., two years), coupled with a
survey of neighbors.
Of course, the community may decide not to include any requirement for permit
renewal at all. Many communities simply rely on neighbor complaints (particularly
those that require notice to neighbors at the time of installation) to ensure
continued compliance. This appears to be the most common approach followed in
the Washington ordinances reviewed for this report.
Using less restrictive requirements for permit renewals will allow the jurisdiction
to concentrate enforcement efforts where they are most needed while at the same
time reducing the regulatory burden on ADU homeowners. [Accessory Units:
State of the Art - Model Zoning, pp. 5-6].
A related requirement found in some ordinances provides for the automatic expiration
of the permit when changes occur causing the ADU to be out of compliance with
the required development standards.
In addition to the conditions which may be imposed by the Planning Director
... all accessory dwelling units shall also be subject to the condition
that such a permit shall automatically expire whenever:
a.The accessory dwelling unit is substantially altered and is thus
no longer in conformance with the plans approved by both the Planning
Director and the Building Official; or
b.The subject lot ceases to maintain at least three off-street
parking spaces; or
c.The applicant ceases to own or reside in either the principal
or the accessory dwelling unit. [Sec. 39.020(D)(12), Everett Zoning
Automatic ADU Ordinance Review
Some communities have adopted provisions that require an automatic review of
ADU ordinances after a certain number of ADU permits have been issued. An automatic
review based on the number of permits issued may be based on a certain number
issued community-wide or the number of permits issued within a single area (e.g.,
census tract), or a combination of these.
At least three (3) months prior to reaching the two thousand five hundred
(2,500) limit on applications or on September 1, 1999, whichever is earlier,
the Department of Construction and Land Use and the Planning Department
shall submit to the City Council a report regarding accessory dwelling
units established, and, if deemed necessary, recommendations for revisions
to the regulations and procedures related to accessory dwelling units.
Within six (6) months of receiving the report, the City Council shall
review the report and consider the recommendations proposed. If the
City has reached or is nearing the two thousand five hundred (2,500)
limit on applications, the City Council shall determine whether to
authorize further permits or otherwise revise the provisions.
If applications are filed for permits for accessory dwelling units which
would cause the concentration of new structures with accessory dwelling
units to exceed twenty percent (20%) of the number of single-family
residences in single-family zones in any one (1) census tract or in
an area bounded by a circle with a radius of one thousand feet (1,000')
from a point where three (3) or more census tracts meet, the Department
of Construction and Land Use shall notify the City Council. Within
three (3) months, that department shall submit a report to the City
Council containing an analysis of the number, location and character
of the single-family structures with accessory dwelling units in the
tract or area exceeding the twenty percent (20%) threshold. The City
Council shall request that the neighborhood planning organization for
the affected neighborhood submit a recommendation within three (3)
months of that request regarding action to be taken. Within six (6) months
of receiving the neighborhood planning organization's recommendation,
the City Council shall review the report and consider recommendations
proposed. The City Council shall determine whether toauthorize further
permits or otherwise revise the provisions. [Sec. 23.44.025(F), Seattle
Land Use Code]
Automatic review provisions may be useful to reassure neighborhood groups that
any problems related to ADUs will be reviewed and dealt with at some point.
If this type of provision is adopted, it may also be useful to include a provision
grandfathering any ADUs that have been constructed before the ordinance is amended
or repealed. This may help to remove any doubts or concerns that homeowners
who legally install ADUs may have about the legal status of their units in the
event that the ordinance is amended or repealed at a later date. [Accessory
Units: State of the Art -Summary of Experience, p. 21]
Most of the Washington ordinances reviewed for this report do not provide for
an automatic ordinance review.
Periodic Reports on ADU Applications
Periodic reporting by the planning department on permit applications may be
useful to monitor the impacts of ADUs in the community. Some communities have
included such requirements to address concerns expressed by neighborhood groups
that unanticipated large numbers of conversions could harm single-family neighborhoods
without some mechanism for periodic monitoring and review. If the number of
conversions is having disproportionate impacts on particular areas in the community,
then, presumably, the city council could step in to correct the situation by
amending the ordinance to either limit or even prohibit additional conversions.
Reports. The Building and Land Use Services Division of the Public Works
Department shall report annually to the City Council regarding ADU applications.
The report shall include: (a) the number of units established; (b) the
geographic distribution of the units; (c) the average size of the units; and
(d) the number and type of completed regulatory enforcement actions. The
ADU ordinance will be reassessed every five years, or sooner, if records show
that 20 percent of the single-family structures within any census tract or
city-wide have ADUs. [Sec. 13.06.196(B)(8), Tacoma Municipal Code]
Biennially (every two (2) years), DCLU [Department of Construction and
Land Use] shall prepare a report for the City Council stating the number
and location of permits issued for new accessory housing units.
[Sec.23.44.025(F), Seattle Land Use Code]
Periodic reporting and monitoring requirements may give reassurance to neighborhood
groups without hindering ADU installations, and may therefore be useful in communities
where neighborhood groups are particularly wary of ADUs. Although experience
around the country shows that actual installation rates will probably be lower
than those predicted by many opponents, adoption of this requirement may be
worthwhile to address neighborhood concerns.
Accessory Apartments in Single-Family Housing, by Martin Gellen, Center
for Urban Policy Research, New Brunswick, NJ, 1985
"Accessory Apartments - Using Surplus Space in Single-Family Houses,"
by Patrick H. Hare, with Susan Conner and Dwight Merriam, Planning Advisory
Service Report Number 365, American Planning Association, Chicago,
IL, December 1981
"Accessory Units: An Increasing Source of Affordable Housing," by
Patrick H. Hare and John Danbury, PM, September 1991
Accessory Units: State of the Art - Report I - Summary of Experience,
by Patrick H. Hare, Washington D.C., December 1989
Accessory Units: State of the Art - Report III - Model Zoning, by Patrick
H. Hare, Washington, D.C., September 1991
Blueprint for Bay Area Housing - A Handbook for Addressing the Critical
Housing Shortage in the Bay Area, Association of Bay Area Governments
and the Bay Area Council, the Local Housing Element Assistance Project, Oakland,
CA, May 1990
Housing Affordability and Density: Regulatory Reform and Design Recommendations,
by Douglas Kelbaugh, Mark Hinshaw and David Wright, prepared for the Washington
State Department of Community Development by the University of Washington College
of Architecture and Urban Planning Department of Architecture, 1992
"Not in My Backyard": Removing Barriers to Affordable Housing,
Advisory Commission on Regulatory Barriers to Affordable Housing, Report to
President Bush and Secretary Kemp, U.S. Department of Housing and Urban Development,
Washington, D.C., 1991
"Planning for An Aging Society," by Deborah A. Howe, Nancy J. Chapman,
and Sharon A. Bagget, Planning Advisory Service Report, Number 451, American
Planning Association, Chicago, IL, April 1994
Pages 4, 5, 10, 11, 16, 17, 32, 33, 37, and 39. Reprinted with permission from
Patrick H. Hare, Creating an Accessory Apartment, (New York: McGraw-Hill
Book Company), 1987
MODEL ACCESSORY DWELLING UNIT
Washington State Department of Community, Trade, and Economic
Development, January 1994
Purpose and Intent
Standards and Criteria
1.An Accessory Dwelling Unit (ADU) is a habitable living unit that provides
the basic requirements of shelter, heating, cooking, and sanitation.
Comment: The Uniform Building Code (UBC) Sec. 1207 & 1208 lists minimum
room sizes for an efficiency unit. The jurisdiction could set up maximum
areas in the Standards and Criteria below, if it so desired.
PURPOSE AND INTENT
A. The installation of an ADU in new and existing single-family dwellings
(hereinafter principal units) shall be allowed in single-family zones subject
to specific development, design, and owner-occupancy standards.
Comment: As required by Senate Bill 5584.
B.The purpose of allowing ADUs is to:
1.Provide homeowners with a means of obtaining, through tenants in either the
ADU or the principal unit, rental income, companionship, security, and services.
2.Add affordable units to the existing housing.
3.Make housing units available to moderate-income people who might otherwise
have difficulty finding homes within the (city/county).
4.Develop housing units in single-family neighborhoods that are appropriate
for people at a variety of stages in the life cycle.
5.Protect neighborhood stability, property values, and the single-family residential
appearance of the neighborhood by ensuring that ADUs are installed under the
conditions of this Ordinance.
STANDARDS AND CRITERIA
A.ADUs shall meet the following standards and criteria:
1.The design and size of the ADU shall conform to all applicable standards
in the building, plumbing, electrical, mechanical, fire, health, and any other
applicable codes. When there are practical difficulties involved in carrying
out the provisions of this Ordinance, the (building official) may grant modifications
for individual cases.
Comment: Construction shall conform to all codes which
are required for any new construction.
2.Certification by the (city/county) Health Department that the water supply
and sewage disposal facilities are adequate for the projected number of residents
must be provided to the building official.
Comment: More applicable in rural areas for septic and wells. It is actually
covered by No. 1 above.
3.Any additions to an existing building shall not exceed the allowable lot
coverage or encroach into the existing setbacks.
Comment: Planning ordinance already in place in most jurisdictions.
4.The ADU may be attached to, or detached from, the principal unit.
Comment: Jurisdictions need to survey their existing housing stock and
neighborhood standards to determine where and how ADUs would best fit
their housing needs. This would allow the most diversity of choice and
honor the uniqueness of each site.
5.Only one ADU may be created per residence in single-family zones. Multiple
detached ADUs may be created in (agricultural) zones, if one of the occupants
of each unit is employed by the property owner.
Comment: The first sentence is to maintain single-family appearance.
The second sentence is appropriate in agricultural zones.
6.The property owner, which shall include title holders and contract purchasers,
must occupy either the principal unit or the ADU as their permanent residence,
but not both, for at least (X) months out of the year, and at no time receive
rent for the owner-occupied unit.
Comment: Owner-occupied units are better maintained, and therefore
the neighborhood will be better maintained. If the owner has to live
on site for more than six months out of the year, they could not own
more than one ADU. This would eliminate speculators/developers from developing
duplexes throughout an area under the guise of calling them ADUs.
7.An ADU may be developed in either an existing or a new residence.
Comment: This would allow new home builders to plan ahead for mother-in-law
type units and thus save money now and time and inconvenience later.
8.In no case shall an ADU be more than 40 percent of the buildings total
floor area, nor more than 800 square feet, nor less than 300 square feet, nor
have more than 2 bedrooms, unless in the opinion of the (building official),
a greater or lesser amount of floor area is warranted by the circumstances of
the particular building.
Comment: Area limitation. See No. 1 under Definition above. The existing
structure, the lot size, or the jurisdiction will determine ADUs
9.The ADU shall be designed so that, to the degree reasonably feasible, the
appearance of the building remains that of a single-family residence.
Comment: To maintain single-family appearance. This is a subjective
evaluation and unless specific design standards are adopted by the jurisdiction,
this may be difficult to consistently apply.
10.The primary entrance to the ADU shall be located in such a manner as to
be unobtrusive from the same view of the building which encompasses the entrance
to the principal unit.
Comment: The second entrance is located this way to maintain single-family
appearance with an attached ADU. Less restrictive than no
second entry on the street side of the principal unit, but it allows
for site restriction that may make a side or rear entry impossible.
11.One off-street parking space, in addition to that which is required by the
Ordinance for the underlying zone, shall be provided or as many spaces deemed
necessary by the (building official) to accommodate the actual number of vehicles
used by occupants of both the primary dwelling and the ADU. Parking spaces include
garages, carports, or off-street areas reserved for vehicles.
Comment: Parking requirements may vary from jurisdiction to jurisdiction
depending on density of neighborhood, existing neighborhood standards,
etc. Other parking options include more than one additional space, tandem
parking, or allowing on-street parking.
12.In order to encourage the development of housing units for people with disabilities,
the (building official) may allow reasonable deviation from the stated requirements
to install features that facilitate accessibility. Such facilities shall be
in conformance with the UBC.
Comment: This is an accessibility issue.
ADUs created prior to (date) shall be registered with the (building official)
for inclusion into the Certificate of Occupancy Program. Application for registration
must contain the name of the owner, the address of the unit, the floor area
of the two dwelling units, a plot plan of the property, evidence of the date
of establishment of the unit, evidence of the use for the six-month period prior
to the application for registration, and a signature of the owner.
Comment: This provision would allow the building official to verify the
compliance of the ADU to the codes, and to require changes as necessary.
Comment: It would be difficult, and very time consuming, to determine
under which codes the ADU was originally constructed.
1.Application for a building permit for an ADU shall be made to the (building
official) in accordance with the permit procedures established in Section (00.0000),
and shall include:
Comment: For building officials plan check.
a.A letter of application from the owner(s) stating that the owner(s) shall
occupy one of the dwelling units on the premises, except for bona fide temporary
absences, (for (X) months out of each year).
Comment: This is an owner-occupancy requirement. Limits the owner
from living in several units at the same time.
2.The registration form or other forms as required by the (building official)
shall be filed as a deed restriction with the (county) Department of Records
and Elections to indicate the presence of the ADU, the requirement of owner-occupancy,
and other standards for maintaining the unit as described above.
Comment: This is for optional use if the owner-occupancy requirement
3.The (building official) shall report annually to the (council) on ADU registration,
number of units and distribution throughout the (city/county), average size
of units, and number and type of complaint and enforcement-related actions.
Comment: This is a local jurisdiction option. This provides a tracking
mechanism on the number of ADUs to determine if changes to the Ordinance
4.Cancellation of an ADUs registration may be accomplished by the owner
filing a certificate with the (building official) for recording at the (city/county)
Department of Records and Elections, or may occur as a result of enforcement
5.This Ordinance shall take effect and be in force five days after passage
and legal publication.
Comment: This is a local jurisdiction option.