The installation of all manufactured homes shall comply with the requirements of this section.

1. (1) Installation of a new manufactured home.

   1. (a) The installation of a new manufactured home must be conducted according to the manufacturer's instructions.

   2. (b) If the manufacturer's instructions do not address an aspect of the installation, you may request:

      1. (i) Specific instructions from the manufacturer; or

      2. (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.

   3. (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.

   4. (d) A manufactured home must have a skirting around its entire perimeter. Skirting must be installed in accordance with 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 the vapor retarder removed and the ground directly below the porch must slope away from the home. Skirting must be vented and allow access to the under floor area in accordance with the manufacturer's installation instructions or as required below if the manufacturer's instructions are not available.

      1. (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.

      2. (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 provide cross ventilation on at least two opposite sides.

      3. (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. The cover must be made of material suitable for skirting or venting as required in this chapter.

      If the manufacturer's skirting and access instructions are not specific, skirting, ventilation and access shall be installed as follows:

   5. (e) A manufactured home site must be prepared in accordance with the manufacturer's installation manual or to the requirements of the Model Manufactured Home Installation Standards 24 C.F.R. Part 3285, Subpart C.
   6. (f) If the home is pit set, a drainage system must be installed to divert groundwater from the underside of the home.

   7. (g) Heat duct crossovers must be installed in accordance with the manufacturer's installation instruction manual or if the manufacturer's instructions are not available, to the requirements in the Model Manufactured Home Installation Standards 24 C.F.R. Part 3285.606.

      Heat duct crossovers must be installed to avoid standing water and installed to prevent compression, sharp bends, and to minimize stress at the connections. In all cases, the duct must be supported at least one inch off the ground (exception to the Model Manufactured Home Installation Standards 24 C.F.R. Part 3285).

   8. (h) 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.
   9. (i) Water heater pans are only required where the installation instructions specifically require a pan for warranty or the home was produced after May 31, 2006. The water heater pan drain line must drain to the exterior of the home. The water heater pan drain line and the PRV drain line must not be interconnected.
   10. (j) Water heater expansion tanks are not required by the department; however, you should check with your local jurisdiction for their requirements prior to installation.
   11. (k) Water piping must be protected against freezing in accordance with the manufacturer's installation instructions or by use of a heat tape listed for use with manufactured homes and installed as required by the heat tape manufacturer's installation instructions.
   12. (l) The testing of water lines, waste lines, gas lines, and electrical systems must comply with 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.

   13. (m) A vapor retarder must be installed under all manufactured homes.

       Joints in vapor retarders must overlap a minimum of twelve inches. Voids, cuts, and tears in the vapor retarder must be patched or repaired with an approved method.

   14. (n) 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. In no case shall clearance be less than twelve inches anywhere under the home and eighteen inches at the heat duct cross over locations.
   15. (o) Heat pump and air conditioning condensation lines must be extended to the exterior of the manufactured home.
   16. (p) Roof ridge cap or ridge vent must be installed as required by the manufacturer's installation instructions.

2. (2) Installation of a relocated manufactured home.

   1. (a) A relocated manufactured home must be installed according to the manufacturer's installation instructions.

   2. (b) If the manufacturer's instructions are not available, you may use either:

      1. (i) The Model Manufactured Home Installation Standards 24 C.F.R. Part 3285; or
      2. (ii) The instructions of a professional engineer or architect licensed in Washington state.
   3. (c) For the installation of a relocated manufactured home, all of the requirements of subsection (1)(c) through (p) of this section must also be followed.
   4. (d) Hot water tank pressure relief valve (PRV) drain lines must be installed in accordance with Sec. 3280.609 of the Manufactured Home Construction and Safety Standards Act (Title 24 C.F.R. Part 3280).
   5. (e) Carbon monoxide alarms shall be installed in accordance with Sec. 3280.211 of the Manufactured Home Construction and Safety Standards Act (Title 24 C.F.R. Part 3280). Carbon monoxide detectors installed in relocated homes are permitted to be battery operated.

[Statutory Authority: Chapters 43.22 and 43.22A RCW. WSR 22-01-193, § 296-150I-0310, filed 12/21/21, effective 1/31/22. Statutory Authority: Chapter 43.22A RCW and 2009 c 464 [564]. 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.]