Foundation in a Flash
Beneath the SIP walls in Carlisle lies a foundation to match — custom-made of 26 precast, insulated concrete panels that were set in place by a crane one day in July and then bolted together. The precast concrete panels are a proprietary system manufactured by Superior Walls, a Pennsylvania-based company, primarily in factories located in the Northeast and upper Midwest, where full basements are the norm. Unlike the systems used in insulated concrete forms (ICFs), which are poured in place, the concrete in the Superior Walls panels is cured in a factory under ideal conditions, resulting in a wall that is virtually flawless and able to withstand 5,000 pounds per square inch of pressure. "You could probably get the same strength from concrete poured in place, but you'd need perfect job-site weather — no cold, no rain, and no blistering heat," says Mel Zimmerman, the company's founder.
Considering their strength, the concrete panels are remarkably thin — a 1 3/4-inch concrete face braced by a top and a bottom plate and concrete "studs" every 2 feet — all of it cast in one monolithic pour around a network of steel reinforcing bars. "It's built like a bridge, only vertical," says Zimmerman, who explains that the greatest pressure on any foundation is not from the weight of the house above but from hydrostatic pressure — the force of the water in the surrounding soil pushing on the walls.
But the system offers more than strength. Each panel is bonded to a foam envelope that provides insulation value up to R-12.5. The mix of the concrete makes it dampproof, so no additional water-resistant treatment is needed. In fact the company warrants against water penetration of its foundation walls for 15 years. "The basement will be a dry and comfortable living space with nine-foot ceilings," commented Zimmerman as he watched a panel being lowered into place on a bed of crushed stone. (Independent footings aren't necessary — they're part of the wall — although Tom will need to pour a slab floor after the foundation goes in.)
Preattached galvanized steel nailers on each "stud" allow Tom to easily finish this basement in drywall, after wiring and plumbing are run. "It's a great system if you're planning to get a lot of use out of your basement," says Tom. "When you look at it that way, it's about the cheapest living space in a new home."
The Carlisle ell and master bedroom foundation, about 237 linear feet, will cost about $21,000. Tom estimates that a poured-in-place foundation with insulation, interior furring strips, and waterproofing would have cost $28,000. But precast systems are not always cheaper than other foundations. The price depends in part on location because the panels are made in many different factories across the country. Any price advantage over poured-in-place would depend on shipping costs, and also the cost of wet-concrete delivery in your area. One thing is clear as workers put the last panel into place: No other foundation goes in as quickly. The company says most foundations are installed in just five hours — with no curing time required. "With a regular foundation," says Tom, "I have to wait several days before I can start laying the sill plates. With this, we're good to go."
