Shallow Frost Protected Foundations

Written By: Paul Hayman, P.E.

You have a manufactured home in a northern state that you want to finance. The engineering certification says the home is placed on grade with no footings. Is the homeowner’s only option to raise the home and pour a frost line protected foundation at a cost of $15,000 and up? It was until recently. Now it can be upgraded for significantly less.

The United States is discovering a foundation design that has been used for decades in Northern Europe. It is called a Shallow Frost Protected Foundation. It is a foundation design that holds reflected geothermal heat from the ground and waste heat from the home under the trailer (or other building) to prevent the ground from freezing. When properly designed, it is perfectly permissible to place a manufactured home on grade even when the local frost line requirement is 42” or greater. How? The perimeter skirting is designed with enough insulation to prevent the ground under the trailer from freezing. Depending on the location, it may just require extra insulation on the inside of the skirting wall and the closing of the vents during the heating season. In colder climates, it may require extra horizontal wings of insulation under the back fill surrounding the house.

The basic design guide is an American Society of Civil Engineers publication ASCE 32.01 Design and Construction of Frost-Protected Shallow Foundations (FPSF). You will hear more about these. The September 1996 Permanent Foundations Guide to Manufactured Housing doesn’t specifically address them one way or another. The new HUD Model Installation Rules that went into effect January 1 explicitly encourages their use. The 2006 International Residential Code has its own requirements for SFPF, but also allows designs compliant with ASCE 32.01. This is a very cost effective way to install a foundation resistant to frost heave. It can be used to upgrade a foundation or installed with a new foundation. It allows an installer not to pour concrete footers under the trailer, which can save a significant amount of money in installation costs.

Not everyone is convinced, though. Some of the northern states are very suspicious of a foundation that doesn’t involve pouring concrete and their building code officials are reluctant to approve them. The tide is changing and you will probably find these in the near future in most northern states.

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)