3285 Manufactured Home Installation Standards

Effective January 1, 2009, HUD has established 3285 Manufactured Home Installation Standards as the model installation standards to provide uniform installations for new manufactured homes throughout the United States. These new installation standards only apply to NEW manufactured homes.

Please note that USED manufactured homes do not fall under the new standards and may still be set up using the installation manual which originally came with the home or by using our generic installation standards in the NC Regulations for Manufactured Homes, 2004 Edition. All new manufactured homes come with installation manuals which meet the requirements of the new 3285 Installation Standards, and must be available to this department during the inspection process.

Major Changes in the 3285 Manufactured Home Installation Standards

Some of the major changes in the 3285 Manufactured Home Installation Standards include:

  • Final leveling of manufactured home – New leveling requirements require the home to be no more than ¼ inch difference between adjacent pier supports.
  • Installation of manufactured homes in flood hazard areas – HUD has adopted minimum installation standards for homes located in Flood Hazard Areas.
  • Site Drainage – Drainage slope around house must slope a minimum of ½ inch per foot away from the foundation for the first ten feet. If gutters are installed, the runoff must be directed away from the home.
  • Ground moisture control – If the space under the home is to be enclosed with skirting or other materials, a 6 mil vapor retarder must be installed to cover the entire ground under the home.
  • Piers – Acceptable piers/materials specification – Pressure-treated wood piers, treated with a water borne preservative, in accordance with AWPA Standard U1-04 for Use Category 4B ground contact applications are now acceptable. End cuts of pressure treated lumber must be field treated in accordance with AWPA M4-02 standards.
  • Pier configuration – Caps – Minimum thickness of solid concrete pier cap blocks has been increased to 4” for all piers.
  • Design procedures for concrete block piers – Maximum pier heights have been reduced: single stacked: max 36 inches (was max 40 inches); double stacked: 36 inches -max 67 inches (was 40 inches - max 80 inches); all piers over 67 inches high (was over 80 inches) must be engineered; single stacked mate-line and perimeter piers: max 54 inches (was 56 inches)
  • Footings – Minimum thickness of poured-in place concrete footings has been increased to 6” thick of 3000 psi concrete. (was min 4”, 2500 psi concrete)
  • Severe Wind Zones – All homes in wind zones II and III within 1500 feet of the coastline must be designed by engineer
  • Water Supply – A pressure-reducing valve must be installed when the local water supply pressure exceeds 80 psi.
  • Water Supply testing procedures – The water system must be inspected and tested for leaks after completion at the site in accordance with the requirements indicated in 3280.612. All water piping in the water distribution system shall be subjected to a pressure test. The test shall be made by subjecting the system to air or water at 100 psi for 15 minutes without loss of pressure.
  • Duct work connections – Minimum width of strapping for flexible duct work must be at least ½” wider than the spacing of the metal spirals encasing the duct.
  • Drainage system testing procedures – The drainage system must be inspected and tested for leaks after completion at the site. The installation instructions must provide testing requirements that are consistent with 3280.612. New allowable on-site testing procedures have been established and mandated by HUD. Drainage and vent system and plumbing fixtures – the waste and vent system shall be tested by one of the three following alternate methods for evidence or indication of leakage. Water test – Before plumbing fixtures are connected, all of the openings into the piping shall be plugged and the entire piping system subjected to a static water test for 15 minutes by filling it with water to the top of the highest vent opening.

    There shall be no evidence of leakage. Air test – After all fixtures have been installed, the traps filled with water, and the remaining openings securely plugged, the entire system shall be subjected to a 2-inch (manometer) water column air pressure test. If the system loses pressure, leaks may be located with smoke pumped into the system, or with soap suds spread on the exterior of the piping (bubble test). Flood level test – The manufactured home shall be in a level position, all fixtures shall be connected, and the entire system shall be filled with water to the rim of the water closet bowl.

    Tub and shower drains shall be plugged. After all trapped air has been released, the test shall be sustained for not less than 15 minute without evidence of leaks. Then the system shall be unplugged and emptied. The wasted piping above the level of the water closet bowl shall then be tested and show no indication of leakage when the high fixtures are filled with water and emptied simultaneously to obtain the maximum possible flow in the drain piping.