Footing/Pier Requirements on Manufactured Homes. What is Required?

Written By: Paul Hayman, P.E.

This is another area that is chock full of misinformation that confuses everyone who tries to make sense of it. What does the HUD Permanent Foundation Guide for Manufactured Homes (PFGMH) require and will this change? Are there different requirements for existing homes as compared to new construction? Let’s look at each separately.

HUD PFGMH New Construction: The footing requirements are that the piers be sitting on a reinforced, poured concrete footing with frost line protection. Local authorities may define frost line, but the PFGMH stipulates a minimum 12 inch deep footing. While the PFGMH implies, depending on your interpretation, that CMU blocks must be mortared together, it does not explicitly state that without referring to examples given in the Appendices. Also, if you do accept the interpretation that the CMU blocks must be mortared together, then, in addition, you also must require the following:

open cells in the CMU blocks filled with concrete and rebar, rebar extending into the poured concrete footing, anchor bolts out of the top of the concrete stack, and the I beam bolted to the stack with no wooden shims. The purpose is to create a single, structurally sound post to attach the I beam to the footing. Eliminate any of the preceding and the structural adequacy is compromised. There are many ways to structurally attach the I beam to the footing that don’t require mortaring the blocks together. The PFGMH allows for such alternative designs. The design performance criteria for piers are that they be able to support the total design load of the home. Materials and methods are not mandated. There are states where CMU blocks are seldom used (AZ). There they use steel support stands rated for the design load.

HUD PFGMH Existing Construction: The existing clause (paragraph 101-2) states that the footing and anchorage must meet the intent of the definition of a permanent foundation contained in the document. The intent of the footing is that the home is protected from frost related heaving and weight related settlement. However, “intent” is a subjective term that ultimately means whatever the engineer says it means. Note that the piers are not mentioned here. A valid interpretation is that the PFGMH is not concerned with the specifics of piers on existing manufactured homes as long as they are adequately supporting the home. I have addressed the use of bonding cement on existing piers in other blogs, but I will repeat my firm belief that bonding cement on dry stacked piers (1) is a complete waste of money, (2) does absolutely nothing to increase the overall strength of the foundation and (3) cannot be properly applied using the manufacturer’s recommendations and (4) is not currently authorized by HUD. Other than that, it is fine.

HUD New Model Installation Rules (MIR): The new HUD rules for new construction take a giant step back from the PFGMH. They do not require poured footings. They do not require concrete anchored tie downs. They specifically allow dry stacked CMU piers (single or double stacked, depending on height). They do not require frost line footings unless the local authority requires it. They allow pier pads made of materials other than reinforced concrete. However, as of now (and who knows how long it will last) these rules apply to new construction only. They are much less vague than the current PFGMH. The foundation design must be the one supplied with the setup manual or it must be engineered and approved by the manufacturer prior to installing it. This rule puts the onus on the manufacturer to approve foundation methods and materials for new construction, but does not address existing construction.

It appears that, at least for a short time, there will be two sets of rules, one for new construction and one for existing. The irony will be that the rules for existing construction will be more stringent than the rules for new construction.

About the Writer. Paul Hayman, P.E., is owner of Hayman Residential Engineering Services, Inc. His company specializes in providing engineering certificates in 49 states. He can be reached at hresanswers@hayman-res.com or www.hayman-res.com.

SOURCE: Published by NAMP Publishing Group, a division of the National Association of Mortgage Processors (http://www.MortgageProcessor.org)