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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.
• 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:
• 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.
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.
• 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 (18.104.22.168)).
(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 . WSR 10-06-043, § 296-150I-0310, filed 2/23/10, effective 4/1/10. Statutory Authority: Chapter 43.22A
RCW and 2007 c 432. WSR 08-12-040, § 296-150I-0310, filed 5/30/08, effective 6/30/08.]