What is the definition of a permanent foundation for a mobile/manufactured home?
Monday, May 20, 2019
The U.S. Department of Housing and Urban Development (HUD) includes this definition of a permanent foundation in their publication Permanent Foundations Guide for Manufactured Housing:
C. Definition of Permanent Foundation
Permanent foundations must be constructed of durable materials; i.e. concrete, mortared masonry, or treated wood - and be site-built. It shall have attachment points to anchor and stabilize the manufactured home to transfer all loads, herein defined, to the underlying soil or rock. The permanent foundations shall be structurally developed in accordance with this document or be structurally designed by a licensed professional engineer for the following:
1. Vertical stability:
a. Rated anchorage capacity to prevent uplift and overturning due to wind or seismic forces, whichever controls. Screw-in soil anchors at not considered a permanent anchorage.
b. Footing size to prevent overloading the soil-bearing capacity and avoids soil settlement. Footing shall be reinforced concrete to be considered permanent.
c. Base of footing below maximum frost-penetration depth.
d. Enclosed basement of crawl space with a continuous wall (whether bear or non-bearing) that separateds the basement crawl space from the backfill, and keeps out vermin and water.
2. Lateral stability. Rated anchorage capacity to prevent sliding due to wind or seismic forces, whichever controls, in the transverse and longitudinal direction.
The underlining in the HUD text above is added by us to highlight three key points. First, a permanent foundation system can either follow the standards of the HUD guide OR be designed by a licensed professional engineer. Second, although it states that the screw-in anchors that are commonly used “are not considered a permanent foundation system,” they can be used in conjunction with a longitudinal stabilization bracing system, and the combination can be certified by a professional engineer as a permanent foundation. And third, the maximum frost penetration depth in Florida is zero inches. A permanent foundation is necessary to get FHA financing for a mobile home.
A different definition of a permanent foundation may be used by local tax officials in the jurisdiction where home will be sited. If the home has had the tow bar, axles, and tires removed, and is secured on a standard “stacked block on pads, with screw-in soil anchors and longitudinal bracing” foundation, then it fits the definition in most areas as a permanent foundation for taxation as real estate instead of personal property.
Also, see our blog posts What happens when a mobile home foundation fails in a hurricane? and Why does Florida have mobile/manufactured home installation standards that exceed HUD requirements? and What are the most common defects in mobile/manufactured home foundation piers?
And go to our HUD-CODE FOR MOBILE HOMES page for a listing of our other HUD-code articles.
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