TechPractices: Bill Eich Construction, Spirit Lake, IA

PATH's Technologies in Practice are large scale housing projects throughout the U.S. where innovative technologies are being installed and used. Information is presented from the viewpoint of builders and remodelers who can use these examples as models for projects of their own.

Summary

Bill Eich Construction is a residential builder/remodeler located in Spirit Lake Iowa. They have been using frost protected shallow foundations (FPSF) in all their projects since 1985.

Bill Eich first learned about FPSF in 1984 when he heard about the technique at a seminar given by Canadian building scientist Joe Lstiburek. He realized the cost-savings potential of this technology and has been using it in both concrete and permanent wood foundations. In 1992 he was contacted by the NAHB Research Center and participated in a project that monitored the performance of FPSF over several winters. At that time he had already used the technology in over 50 homes and additions.

Details

Frost protected shallow foundations work by decreasing the frost depth, permitting footings to be closer to the surface than local practice and code requirements. The key to this technology is insulation, which extends vertically down the exterior face of the stem wall and horizontally away from the footing. This insulation traps ground heat and holds it at the foundation. The heat raises the ground temperature which decreases the frost depth.

Since the technology relies on ground heat, it can be used for unheated structures such as garages as well as heated homes. The only difference is that insulation requirements are more stringent with unheated structures since there is no additional heat source from the home into the ground. The thickness and placement of the insulation varies based on the climate and foundation design. The Spirit Lake climate requires 2 inch thick insulation for his climate, placed both vertically along the foundation stem wall and extending horizontally from the footing.

Installation/Construction

Deep trenches are not required which eliminates shoring requirements and improves job-site safety. For example, Bill Eich has reduced the footing depth for his homes from 48 inches to 16 inches. The shallower trench also helps shorten the construction schedule by several days by eliminating or shortening construction steps; including trenching with a back hoe, storing or hauling excavated dirt, decreasing fill requirements, and eliminating much if not all soil compaction requirements. Finally, insulating the ground extends the time during which concrete can be poured into December. The insulation prevents the concrete from freezing before it cures.

Benefits/Costs

The average savings of the FPSF is between $11 and $15 per linear foot of foundation. Bill reports savings associated with less excavation, concrete, and backfill requirements. Potential savings are dependent on the required frost depth set by the local jurisdiction. In general, this technology is worth considering when the frost depth is 30 inches or greater.

Code/Regulatory

This technology is currently recognized in the 1995 CABO One- and Two- Family Dwelling Code and is in the final draft of the proposed International Residential Code. Bill advises that builder's work closely with local building officials when proposing to use this technology. There is considerable engineering evidence on its effectiveness, which will help the code official to evaluate your proposed design. The NAHB Research Center published the Design Guide for Frost-Protected Shallow Foundations, which enables a builder to determine his requirements for different types of construction at locations throughout the United States. This report is available from the Research Center as well as HUD USER. Bill Eich reports that over a million structures in Scandinavia have frost-protected foundations.

Feedback

Customer reaction to frost protected shallow foundations is very positive. The trapped ground heat not only decreases the frost depth but also increases the temperature of the concrete floor slab. People like warm floors, it makes their home comfortable and more livable.

One North Dakota builder states that they saved from 1.1 to 2.4 percent on the total cost of the home using the FPSF, depending on how it is implemented. A builder in Iowa saved 3.8 percent on the total cost of the home and four days of construction time in a recent project featuring the FPSF.

Contact(s)

Do you have a specific question? Try the contacts listed below:

Bill Eich Construction
P.O. Box S
Spirit Lake, IA 51360
712-336-4438

Department of Housing and Urban Development
HUD USER
202-708-3178
http://www.huduser.org

Journal of Light Construction
September 1996 issue
802-879-3335
http://www.jlconline.com