Frost-protected foundations offer big savings on materials and labor. By Matthew Power
By now, most builders have heard of frost protected shallow foundations (FPSF). The recent publication of standards in the International Residential Code (see R403.3) makes the systems even more attractive. Just how much money can a builder save with a shallow-frost versus a full foundation? It depends on the climate.
Alternative energy experts suggest that homes in hot, southern climes would see little or no cost savings with a FPSF--but in cold regions, the shallow, insulated walls amount to both immediate and ongoing (homeowner) savings.
Their formula: Figure that a full foundation uses seven yards more concrete than a FPSF, resulting in 43 percent savings on your cost of concrete. Subtract from that amount the cost of creating a perimeter of rigid foam (EPS-type) insulation. Finally, subtract 70 percent from your normal costs for trenching a standard foundation wall, to determine your overall savings.