How To Look At A House
McGarry and Madsen's home inspection blog for buyers of
site-built, mobile/manufactured and modular homes
What is a pit set mobile home?
Thursday, August 30, 2018
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:
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.
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Here’s links to a collection of our blog posts about MOBILE/MANUFACTURED HOMES:
Photo - Michael Butler, Fast Track Foundation Systems
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