Accessory Dwelling Units Publication

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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 use

Introduction
Why the Interest in ADUs?
Benefits
Regulatory Issues and Options
Zoning Regulations for ADUs - Issues and Options
References
Appendices

Foreword

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 their communities.

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, April 1992.

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

Introduction

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 applicable.

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 and forms.

Why the Interest in ADUs?

Three factors have spurred the recent interest in accessory dwelling units—the 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.

Demographic Trends

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 housing opportunities.

State Laws

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 and development;
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

[RCW 36.70A.070]

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 A).

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.

Benefits

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.

Community Benefits

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 area.

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.

Homeowner Benefits

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 home.

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 generations.

Accessory Apartments in Single-Family Housing
Martin Gellen

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.

Tenant Benefits

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 congestion.

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 assistance.

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 are:

What are the community's housing goals and how will these affect the regulation of ADUs?
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.

Community Goals: Balancing Neighborhood Concerns with the Need for Affordable Housing

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 community neighborhoods.

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 services.
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

Neighborhood Concerns

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 standards.

Homeowner Needs

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 Housing, 1985]

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 height requirements.

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 process.

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

Definitions

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 ADU features.

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.

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.

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.

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.

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 illegal units.

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 applicant’s 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 of opponents.

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.

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 and appearance.

Owner-Occupancy Requirements

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.

'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.

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 ....

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 ....

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.

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.

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.

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 for habitation.

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 restriction.

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.

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 Code]

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.

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.

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]

Parking Requirements

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 parking.

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 Municipal Code]

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.

Design/Appearance Standards

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.

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.

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 accommodate ADUs.

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 ...

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 Unit Ordinance]

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.

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 No.25624]

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.

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.

Illegal ADUs

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 Municipal Code]

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.

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
Martin Gellen

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 Code]

Density Controls

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.

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 dwelling ...

"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.

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.

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.

Recording Requirements

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.

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.

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.

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 capacities.

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.

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, p. 6]

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.

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.

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.

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 additional expense.

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.

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.

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.

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 Code]

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.

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.

References

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

Illustration Credits

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

Appendix A

MODEL ACCESSORY DWELLING UNIT

ORDINANCE RECOMMENDATIONS

Washington State Department of Community, Trade, and Economic Development, January 1994

SECTIONS:

Definitions

Purpose and Intent

Standards and Criteria

Grandfathering

Application Procedures

DEFINITIONS

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 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.

Comment: Area limitation. See No. 1 under Definition above. The existing structure, the lot size, or the jurisdiction will determine ADU’s size.

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.

GRANDFATHERING

1.Option 1.

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.

Option 2.

Ignore.

Comment: It would be difficult, and very time consuming, to determine under which codes the ADU was originally constructed.

APPLICATION PROCEDURE

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 official’s 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 is adopted.

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 are needed.

4.Cancellation of an ADU’s 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 action.

5.This Ordinance shall take effect and be in force five days after passage and legal publication.

Comment: This is a local jurisdiction option.