Manufactured Housing Anchorage Requirements

Written By: Paul Hayman, P.E.

Exactly what kind of anchorage is a manufactured home required to have? A better first question is: What exactly is “anchorage” on a manufactured home? A manufactured home must be built to withstand external forces on it caused by wind and/or seismic events. “Anchorage” is the system that ties the home down and prevents it from being damaged by winds or minor earthquakes. Often the terms “anchorage” and “tie downs” are used interchangeably. The forces that the home must withstand include those that tend to lift the home straight up off the foundation and those that tend to move it sideways in one direction or another. “Vertical anchorage” prevents the home from being lifted off the foundation while “lateral anchorage” prevents it from moving sideways in any direction.

The September 1996 Permanent Foundations Guide for Manufactured Housing lists its anchorage requirements in the definition of permanent foundations. Under vertical stability, it requires “ rated anchorage capacity to prevent uplifting and overturning due to wind or seismic forces, whichever controls. Screw in soil anchors are not considered a permanent anchorage [paragraph 110.C].” For lateral stability, it requires “rated anchorage capacity to prevent sliding due to wind or seismic forces, whichever controls, in the transverse and longitudinal directions [ibid].”

Traditionally, there are a number of ways to anchor a manufactured home to the ground with the most common being a series of ground anchors with galvanized straps attached to the I beams that support the home. Depending on the state, they have been placed anywhere from a little over five feet apart (FL) to twelve feet apart (many states). Most states don’t have specific requirements for anchorage. A few states that have large numbers of manufactured homes such as Florida, Arizona and California have adopted very specific requirements and many other states are following suit, but it is important to note that the engineering requirements for manufactured home foundations for loan purposes are independent of any state requirements.

The HUD requirements are federal requirements and the HUD manual is not particularly clear in stating exactly what constitutes proper anchorage. For example, in the quotes above note that soil anchors are not permitted for vertical anchorage, but there is no such restriction for lateral anchorage. Most engineers interpret this as a requirement that all tie downs be anchored into concrete even though that is not what is says. Add to this the fact that no state requirements and no manufacturer requirements mandate the use of concrete anchored tie downs and you get a sense of the confusion. Homes that fully meet state and manufacturer anchorage requirements may not meet HUD anchorage requirements.

I have a hard time explaining to a homeowner in Florida that his home that fully meets Florida state requirements and has withstood several hurricanes unscathed does not have a “permanent foundation” as defined by HUD. To this point, I have just been talking about new construction. Take this amount of confusion and multiply it by ten, and you have an idea of the amount of confusion surrounding existing construction. That is because, according the September 1996 HUD manual, anchorage on existing construction need only meet the “intent” of the new requirements. That turns the whole issue into a subjective quagmire in which every engineer has his own opinion of what constitutes “intent.”

The new HDU Model Installation Rules, which have not gone into effect yet, attempt to solve this problem. But until then, required HUD anchorage is defined by whatever the engineer who inspects the property says. An engineer knowledgeable of HUD rules can save your borrower thousands of dollars in unnecessary upgrades.

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)