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 separates 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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Here’s links to a collection of our blog posts about MOBILE/MANUFACTURED HOMES:

• How can I tell if a mobile/manufactured home will pass a foundation certification inspection?

• Do manufactured/mobile homes have more foundation problems than site-built homes? 

• Where can I file a complaint if I have problems with my new or used manufactured/mobile home in Florida?

• What are the most common defects in mobile/manufactured home foundation piers?

• How do I determine the age of a very old mobile home?

• What is a "HUD label verification letter" for a mobile/manufactured home?  

• When did a ground cover vapor barrier (plastic sheet) become required under a mobile/manufactured home? 

• Is it safe to go under a mobile home? 

• Are older mobile homes unsafe? 

• What do I need to know about buying a foreclosed mobile home? 

• Does it make sense to buy an older mobile home and remodel it? 

• Where do I find the vehicle identification number (VIN) on a mobile home? 

• How do I find out how old a mobile home is and who manufactured it?

• What is the right price for a used mobile home?

• How energy efficient is a mobile home?

• When were the first double-wide mobile homes manufactured?

• How do I upgrade my old (pre-1976) mobile home to meet HUD standards?

• What size air conditioner is right for my mobile home? 

• Can you move an older mobile home in Florida? 

• What does the HUD tag look like and where do I find it on a mobile home? 

• Can you put a zone 1 mobile home in Florida?

• How can I remove water under my mobile home?

• What's the differences between a trailer, a mobile home, a manufactured home, and a modular home? 

• What is a D-sticker mobile home? 

• What are the tie-down requirements for a mobile home?

• How fireproof is a mobile home?  

• Can I install a mobile home myself?

• What is a Park Model mobile home?  

• Does an addition to a mobile home have to comply with the HUD Code? 

• What walls can I remove in a mobile home?

• What can I do to prevent dampness and mold in my mobile home? 

• How can I tell if a mobile home is well constructed?

• How can I tell the difference between a manufactured home and a modular home?

   Visit our MOBILE/MANUFACTURED HOMES page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.