Frost-Protected Shallow Foundations in Residential Construction
This report addresses an investigation and demonstration of frost-protected shallow foundations. Specific objectives included field testing the frost-protected shallow foundation technology on homes in the United States; investigating the cost-effectiveness of the technology; and developing design and construction guidance for builders, designers, and code officials. A frost-protected shallow foundation is a practical alternative construction method in cold regions where more costly deep foundation construction methods are used. The most extensive use of the technology has been in the Nordic countries, where over 1 million homes have been constructed successfully over the last 39 years. Demonstration homes were constructed at three locations for the project: Fargo, North Dakota; Spirit Lake, Iowa; and Williston, Vermont. The design for each site used a conservative application of Norwegian Building Institute 1987 recommendations. The designs also relied on 100-year return design air-freezing indices, prepared by the National Oceanic and Atmospheric Administration of the U.S. Department of Commerce. The builders for the demonstration homes each realized cost savings compared with their conventional construction practices. However, there was a wide variability in costs due primarily to different degrees of familiarity with the technique and to differences in house type. Cost savings ranged from 1.1 to 3.8 percent of the total home sales price.
Phase II: Final Report
This report is the second and final phase of an investigation and demonstration of the frost-protected shallow foundation (FPSF) technology. A FPSF is a practical construction method in cold climates where more costly conventional foundation methods are used. The report found that houses and other structures may be built on shallow, slab-on-grade foundations in cold climates when properly insulated to protect against frost heave. The demonstration homes performed well and provided substantiating evidence for the FPSF techniques design recommendations. FPSF construction provides a cost-effective alternative to conventional foundation construction in the United States. Cost savings to the home buyer range approximately 1 to 4 percent of the cost of a conventional slab-on-grade home and are even greater when compared to basement construction. Experience has shown that the FPSF technology may be used to increase the energy efficiency of new houses at a minimal or reduced construction cost.