What is a Permanent Foundation on a Manufactured Home?

On November 16th, 2009, posted in: Residential by

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This seems like a perfectly natural question, but for a long time, the only answer I could give was, “Who wants to know?”  There were multiple definitions of a permanent foundation and it depended on who was asking the question.  Depending on who you asked, whether it be the VA, FHA/HUD, insurance companies, conventional mortgage underwriters, state agencies, local building authorities or manufactured home manufacturers, you received a different answer, or sometimes no answer at all.

These days the answer seems to be converging to the HUD/FHA standard, which is ironic, because it’s the most confusing, controversial standard out there.  The standard to be used is a specific document, the HUD Permanent Foundations Guide to Manufactured Housing (PFGMH) dated September 1996.  Sometimes it’s given a document number although the number doesn’t appear anywhere in the guide itself.  Should you want a copy, you can download a pdf version from HUD’s website.  However, don’t get too attached to it as HUD has published a new standard, the Model Installation Standard, which should have gone into effect last October, but has been indefinitely delayed.  The PFGMH is primarily a cookbook of HUD approved designs for manufactured home foundations.  The only trouble is that they are universally despised

For example, the most common method of anchoring a manufactured home to the ground is by using galvanized straps and ground anchors, a method accepted by virtually all states recommended by most manufacturers.  The PFGMH prefers to attach the home to the ground through the stack of CMU piers underneath.  To do this, one needs to not only mortar the CMU blocks together, but also (1) fill the voids with concrete, (2) run rebar into the poured concrete footer beneath the pier, (3) add an anchor bolt at the top, and (4) bolt the I Beam to the stack with the anchor (preferably without wood shims).  This is very elegant from an engineering perspective, but extremely expensive from a set up stand point as it means that the piers have to be in place before the home arrives on site, thereby requiring every home to be craned or rolled onto the foundation thereby adding thousands of unnecessary dollars to the set up costs.  If this sounds overly complicated, it is.  In fact, HUD has completely backed off this requirement in the newer Model Installation Standards, but, until they go into effect, the PFGMH must be followed.

What’s a homeowner to do?  Fortunately, there is an escape clause.  The PFGMH allows an engineer to design an alternative foundation from scratch.  He just has to jump through a number of hoops to do so.  The foundation has to do basically three things: (1) keep the home from sinking into the ground, (2) keep the home from heaving due to frost driven soil expansion and (3) protect the home from wind/seismic driven vertical and horizontal forces.  There are a number of ways to accomplish this and we will discuss them in future articles.

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