FHA Guidelines for Double-wide Foundations

The Federal Housing Administration provides mortgages to buyers of double-wide homes, but there are certain stipulations. Double-wide mobile homes are manufactured homes, and the FHA only approves mortgages for homes with permanent foundations. If the home does not meet the FHA criteria of "permanent dwelling," it is ineligible for financing as it is considered personal property, not real estate. The FHA requires that a mortgage cover both the manufactured unit and the site for a 30-year mortgage. The U.S. Department of Veterans Affairs has similar permanent foundation rules for its mortgages.

Double-wide mobile homes get their name because they are two units joined together. The two units are shipped separately to the building site, where they are joined together. Older double-wide homes have a visible seam where the two units are connected, but modern varieties hide the connection. Double-wide homes are at least 20 feet wide, with a length of less than 90 feet. They range between 1,000 to 2,300 square feet in size, which doesn’t count porches, decks or other additions.

While the double-wide is considered a mobile home, it’s not the kind you can easily pick up and move, unlike a single-wide. First of all, it has two sections and requires two trailers. Secondly, double-wides look like site-built homes, and buyers tend to consider them the equivalent of site-built homes when it comes to moving them. The FHA isn’t the only lender that will only approve mortgages for dwellings with permanent foundations, so unless the property is paid for with cash, most double-wides are permanent structures for all intents and purposes.

The FHA follows the U.S. Department of Housing and Urban Development guidelines for permanent foundations for manufactured housing. If the double-wide home had any wheels or axels, they require removal before the home is affixed to a permanent foundation. The design standards for the foundation are based on criteria for conventional, site-built housing. Acceptable foundation materials include concrete, masonry or treated wood.

Foundation walls must extend a minimum of 8 feet above the foundation’s finished grade at every point. Masonry or concrete foundation walls are 6 inches, with a reinforced concrete footing thickness of at least 6 inches or 1. 5 times the footing projection’s length from the foundation wall, whichever is greater. The bottom of the footings must reach the site’s maximum frost penetration depth. Only clean material free of wood scraps or debris may be used for back fill.

At minimum, a 6-millimeter plastic vapor barrier must cover the dirt floor beneath the double-wide. Many people install a concrete floor instead, but the point is protecting the home from moisture. If a homeowner wants to spend the money, he can install a basement beneath the home. While this is the best type of foundation, other options include the slab, which is inexpensive and easily installed, or the pit, which is not as good as a basement foundation but does give a double-wide the appearance of a site-built home.