Surface Bonding Cement and HUD Requirements for Existing Manufactured Homes

Written By: Paul Hayman, P.E.

It is very common to encounter a type of surface bonding cement under manufactured homes that has been applied as an upgrade to bring the foundation into compliance with HUD standards. However, I have never been able to understand how or why this is the case. There seems to be an interpretation among some engineers that the September 1996 Permanent Foundations Guide to Manufactured Homes (PFGMH) requires that CMU blocks always be mortared together and that the use of such a bonding cement will meet that requirement. In my opinion, this is wrong on both counts.

First, there is nothing in the definition of a permanent foundation in the PFGMH that requires block stacks to be mortared together. There is a section that does address masonry piers. The most common quote is taken from section 503.4 which states “All masonry piers and walls shall have mortared bed and head joints.” What is usually left out is the following statement, “Reinforcing and grouting shall be in accordance with the foundation concept selected from Appendix A.” Appendix A is a collection of pre-approved designs which are guaranteed to meet HUD requirements. When you look closely at what this requires, you find that the total approach requires several components seldom found, including: (1) a poured concrete footer, (2) voids in the CMU filled with concrete, (3) rebar connecting the CMU to the footer, (4) an anchor bolt coming out of the top of the stack and (5) the I beam securely bolted to the stack through the anchor bolt (with no wooden shims). This is a very complete structural stack that will meet every HUD requirement. Unfortunately, it is rarely encountered because it unnecessarily adds thousands of dollars to the set up costs and is not structurally necessary.

However, this entire design is not mandatory for existing construction for two reasons. One, the PFGMH clearly allows alternative designs that do not require the mortaring of CMU blocks. The PFGMH includes possible designs in the Appendix, but those designs are only examples and are not mandatory. Two, the PFGMH clearly addresses requirements for existing foundations in Chapter “101-2. EXISTING CONSTRUCTION. . . Upgrade of existing anchorages and footings shall meet the intent of the definition of permanent foundation stated herein.” Note that only the anchorages and footings are required to meet the “intent” of the new requirements. Piers stacks on existing construction do not have to meet the same requirements as new construction. So even if the mortared CMU blocks were universally required for new construction, which they aren’t, existing construction doesn’t have to meet these requirements.

This should be enough to eliminate the use of this product in this application, but there are several other even better reasons why it should not be used. The first is a matter of common sense. A manufactured home sitting on a pier stack will slip at the point of least resistance. On a pier stack, the point of least friction is where the I beam sits on the wooden shims—smooth surface on smooth surface. If that is not addressed, and the use of bonding cement does not touch this area, it doesn’t matter how strong the stack beneath the I beam/wood shim connection is, the stack will still slip at exactly the same applied force as it did before. The surface bonding cement does absolutely nothing to actually strengthen the overall foundation, so why use it?

Another reason is administrative. The usual HUD document referenced is the HUD Materials Release 907f which addresses the use of Bonsal Surface Bonding Cement in various applications. There are three reasons why this document is not applicable to existing foundations on manufactured homes:

1. Nowhere in this document is the specific application of upgrading foundations on manufactured homes even mentioned. This application was designed for agricultural block buildings, not residential housing;

2. The document expired in October 2007. I can find no evidence on HUD’s website (or anywhere else) that it was reviewed or re-released. The document clearly states ” Failure to apply for a renewal or revision shall constitute a basis for cancellation of the MR.” Based on its expiration, the MR can no longer be used;

3. Most importantly, the manufacturer’s installation instructions must be followed and their requirements are such that this product cannot be used for existing manufactured home foundations. Under the manufacturer’s instructions are statements such as “The first course of concrete blocks is laid in a full mortar bed,” “Bonsal. . . shall extend down to the top of the footing.” This product is designed to be used in buildings that (1) have a poured concrete footing and (2) have the first row of blocks mortared to that footing. There is not a manufactured home in this country that meets these two requirements that doesn’t have the rest of the block mortared. I have seen this product used in hundreds of manufactured homes and in every one, the piers are sitting on grade.

Based on the above, I never recommend the use of surface bonding cement to upgrade a foundation to compliance with HUD rules. However, when I encounter a foundation with this surface bonding cement, I usually don’t require the homeowner to do anything else because he has already spent (sometimes) thousands of dollars on this. It is not fair to a homeowner to continually require additional upgrades because the engineers can’t agree on what should be required.

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)