Until recently, ground slab construction has not been possible in areas with shifting soils, but a new system allows builders to use concrete slabs where they previously were confined to more expensive pier-and-beam foundations. The Tella Firma system, which has been used with success by Lennar Corp., relies on concrete support piers, post-tension cable supports, and a threaded (bolt-based) system to gently and permanently lift a standard five-inch concrete slab to a target height of 1-1/2 times higher than the highest possible ground movements—up to a maximum of 13 inches.
Jim Fontaine, Tella Firma’s chief executive officer, says his company’s product adds around $2,000 to the cost of concrete slab construction—which he likens to an insurance policy against cracks and other damages.
