When a manufactured home is installed very close to ground level, making it look more like a site-built home, it has a “pit set” foundation. Because access to the bottom structure of the mobile home is necessary for maintenance and ventilation, a shallow pit must be dug under the footprint of the home. Then a structural stem wall is built following the shape of the perimeter of the home. It provides support under the exterior walls and also acts as a retaining wall to keep the surrounding soil from migrating back into the pit over time. Interior piers along the marriage line and at support points for the steel beams are still necessary, the same as in a regular installation. 

   As you might imagine, a pit set installation is much more expensive—and requires more engineering—than a standard, elevated installation that takes advantage of economical, stacked block piers on pads and plastic skirting. But the photo above demonstrates that it can be very difficult to tell a pit set from a site-built home. A site-built addition, such as the garage in the photo, can further camouflage the fact that it’s a manufactured home. But vent panels near the ground for the crawl space are a clue that you are looking at a pit set. 

   Because the home’s floor joists are secured from uplift by structural connections to the perimeter stem wall and foundation, one advantage of the pit set foundation system is that it can be expected to meet the requirements for a real property mortgage. The cost savings over the life of the loan compared to mobile home financing, along with the availability of more sources of funding, are a definite plus. 

   We have inspected only a few pit set homes in our North Central Florida area over the past decade and, unfortunately, have found that they are not well suited for sites where the water table rises close to the ground during the wet season. The result is a house over a mucky pond for part of the year. One pit set that we inspected was a foreclosure, mold-filled and abandoned by the owner—the result of an especially long and wet rainy season that the home spent sitting over standing water. But, when sited correctly, a pit set can be a good alternative for a manufactured home installation.

   To learn more about pit set foundations, we suggest visiting the website of Harrison Engineering LLC, a company that specializes in providing foundation plans for manufactured homes nationwide, at:

http://www.mobilehomefoundation.com/foundation_types_mhf.php?tab=Pit-Set_Crawlspaces

   Fast Track Foundation Systems, of Fort Bragg, CA, offers a proprietary system that can be used for pit set homes, which they call “low set.” See their website at www.anchorpanel.com for more info.

    Also, see our blog post How can I remove water under my mobile home? and Is it safe to go under a mobile home? 

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Here’s links to a collection of our blog posts about MOBILE/MANUFACTURED 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?  

• 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? 

• 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. 

Photo - Michael Butler, Fast Track Foundation Systems