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No Footing

Unlike conventional foundations, Superior Wall panels do not require concrete footings. Many builders flinch at the thought, but when typical residential wall loads are compared with average soil bearing capacities (2,500 pounds per square foot or higher), standard spread footings are generally oversized. A poured concrete foundation often represents half of the total design weight of a house. Since an 8-foot-tall prefabricated panel weighs in at about 285 pounds per linear foot (less than a third of the weight of a 10-inch poured-in-place concrete wall), total house loads can be reduced by as much as 30%. The panels are designed to support more than 4,000 pounds per linear foot, and point loads of up to 71/2 tons can be supported by tripled concrete studs. Beam pockets capable of supporting 10,000 pounds can be cast into the wall. The company reviews the builder’s plans, and designs the panels to support the project’s particular loading requirements. Superior Wall panels have been approved for use in areas under the BOCA code. According to the company, over 15,000 foundations have been installed, and there has been no structural failure attributed to the design or manufacture of the system.

Assembling the Panels

Lifting pockets are cast into each panel, and specially designed nylon straps are looped over the crane’s spreader bar to pick up each panel. Panels are bolted together at the top and bottom with 1/2-inch galvanized machine bolts inserted through precast recesses in the top and bottom plates (Figure 2).

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Figure 2. Half-inch bolts, inserted through cast recesses, fasten the panels together at the top and bottom plates (left). A bead of urethane sealant is applied to the butt joints, and after the panels are drawn up tight, the joint is caulked again on the interior and exterior (right). To seal the joint, a bead of high-quality urethane caulk is applied to the panels just before they’re butted together. After the panel bolts are drawn up tight, two additional beads of caulk are run on the exterior and interior of the joint. Outside corners are cast as miter joints, and bolted together and sealed in the same manner as butt joints. In most cases, the concrete slab is poured before backfilling. The slab acts as a brace, preventing the bottom of the panels from kicking in as the foundation is backfilled. In areas where there will be no slab (a crawlspace, for example), 2x6 diagonal bracing is fastened to the bottom of the foundation panel and tied into the floor joist system above. The company claims that no additional waterproofing treatment is needed. By preparing the site so groundwater is readily diverted from the foundation, moisture problems are avoided. If I were building in an area with a high water table, I’d still apply a foundation coating or membrane, and use a granular backfill material.