WAC 296-150I-0310
What instructions are used for a
manufactured home installation? To the extent that the
installation of a manufactured home is not covered by a
manufacturer's, engineer's, or architect's instructions, the
manufactured home shall comply with the installation
requirements of this section.
(1) Installation of a new manufactured home.
(a) The initial manufactured home installation must be
conducted according to the manufacturer's instructions.
(b) If the manufacturer's instructions do not address an
aspect of the installation, you may request:
(i) Specific instructions from the manufacturer; or
(ii) Specific instructions from a professional engineer
or architect licensed in Washington state.
For example:
• A manufactured home is installed over a basement and
the manufacturer's instructions do not address this
application;
• A manufactured home is installed on a site where the
specific soil bearing capacity is not addressed in the
manufacturer's instructions.
(c) All manufactured homes installed in Washington state
must be permanently anchored except for those installed on
dealer lots. On dealer lots, temporary sets are permitted
without anchoring being installed. A manufactured home must
be anchored according to the manufacturer's installation
instructions or according to the design of a professional
engineer or architect licensed in Washington state. Local
jurisdictions may not prescribe anchoring methods.
(d) A manufactured home must have a skirting around its
entire perimeter. It must be installed per the manufacturer's
installation instructions or if the manufacturer is not
specific, to the standards in this section. Do not enclose
with skirting areas under recessed entries, porches or decks,
(whether constructed as part of the home or added on-site)
unless skirting is of the fully vented type and installed so
as to allow water to freely flow out from under the home.
Porch areas open to the crawl space area of the home must have
ground cover removed; ground directly below the porch must
slope away from the home. It must be vented and allow access
to the under floor area per the manufacturer's installation
instructions or per the standards below if the manufacturer's
instructions are not available.
If the manufacturer's skirting and access instructions
are not specific, skirting, ventilation and access shall be
installed as follows:
(i) Skirting:
• Must be made of materials suitable for ground contact.
• Metal fasteners must be made of galvanized, stainless
steel or other corrosion-resistant material.
• Ferrous metal members in contact with the earth, except
those made of galvanized or stainless steel, must be coated
with an asphaltic emulsion.
• Must not trap water between the skirting and siding or
trim.
• Must be recessed behind the siding or trim.
(ii) Ventilation:
For homes sited in a flood plain, contact the local
jurisdiction regarding proper skirting ventilation. Except
for those manufactured homes sited in a flood plain, all
skirting and vent openings must:
• Be covered with corrosion-resistant wire mesh to
prevent the entrance of rodents. The size of the mesh opening
cannot exceed 1/4 inch.
• Have a net area of not less than one square foot for
each one hundred fifty square feet of under floor area.
• Be located as close to corners and as high as practical
and they must provide cross ventilation on at least two
opposite sides.
(iii) Access:
• The under floor area of a manufactured home must have a
finished opening at least eighteen inches by twenty-four
inches in size.
• Opening must be located so that all areas under a
manufactured home are available for inspection.
• Opening must be covered and that cover must be made of
metal, pressure treated wood or vinyl.
(e) A manufactured home site must be prepared per the
manufacturer's installation manual or per ANSI A225.1, 1994
edition, section 3.
(f) Heat duct crossovers must be installed per the
manufacturer's installation instruction manual or per ANSI
A225.1 or the following instructions if the manufacturer's
instructions are not available:
Heat duct crossovers must be supported at least one inch
above the ground by strapping or blocking. They must be
installed to avoid standing water. Also, they must be
installed to prevent compression, sharp bends, and to minimize
stress at the connections.
(g) Dryer vents must exhaust to the exterior side of the
wall or skirting. Dryer ducts outside the manufactured home
shall comply with the dryer manufacturer's specifications or
shall be made of metal with smooth interior surfaces.
(h) Hot water tank pressure relief lines must exhaust to
the exterior side of the exterior wall or skirting and must
exhaust downward. The end of the pipe must be at least six
inches but not more than two feet above the ground.
(i) Water heater pans are only required where the
installation instructions are specific for warranty or the
home was produced after June 2006. The pressure relief line
must exit the skirting of the home as well as the relief line
for any pan installed and not to be interconnected.
(ii) Expansion tanks are not required by the department;
however, you may want to check with your local jurisdiction
prior to installation of your water heater.
(i) Water piping must be protected against freezing as
per the manufacturer's installation instructions or by use of
a heat tape listed for use with manufactured homes and
installed per the heat tape manufacturer's installation
instructions.
(j) The testing of water lines, waste lines, gas lines,
and electrical systems must be as per the manufacturer's
installation instructions. If the manufacturer's installation
instructions require testing of any of these systems, the
local jurisdiction is responsible for verifying that the tests
have been performed and passed. Electrical connections and
testing are the responsibility of the electrical section of
labor and industries except where a city has assumed the
electrical inspection responsibilities for their jurisdiction.
In that case, the city's electrical inspectors are responsible
for the electrical connections and testing.
(k) During the installation process, a ground cover must
be installed under all manufactured homes. The ground cover
must be a minimum of six-mil black polyethylene sheeting or
its equivalent (exception to ANSI A225.1 (3.5.2)). The ground
cover may be omitted if the under floor area of the home has a
concrete slab floor with a minimum thickness of three and
one-half inches.
(l) Clearances underneath manufactured homes must be
maintained at a minimum of eighteen inches beneath at least
seventy-five percent of the lowest member of the main frame
(I-beam or channel beam) and the ground or footing. No more
than twenty-five percent of the lowest member of the main
frame of the home shall be less than eighteen inches above the
ground or footing. In no case shall clearance be less than
twelve inches anywhere under the home (exception to ANSI
A225.1 (4.1.3.3)).
(m) Heat pump and air conditioning condensation lines
must be extended to the exterior of the manufactured home.
(2) Installation of a relocated manufactured (mobile)
home.
(a) A relocated manufactured home installation should be
conducted according to the manufacturer's installation
instructions.
(b) If the manufacturer's instructions are unavailable,
you may use either:
(i) The American National Standard Institute (ANSI)
standard ANSI A225.1 - Manufactured Homes Installation, 1994
edition instructions; or
(ii) The instructions of a professional engineer or
architect licensed in Washington state.
(c) If either (b)(i) or (ii) of this subsection is used,
all of the requirements of subsection (1)(c) through (m) of
this section must also be followed.
[Statutory Authority: Chapter 43.22A RCW and 2009 c 464
[564]. 10-06-043, § 296-150I-0310, filed 2/23/10, effective
4/1/10. Statutory Authority: Chapter 43.22A RCW and 2007 c
432. 08-12-040, § 296-150I-0310, filed 5/30/08, effective
6/30/08.]