EXAMPLES FROM THE DEMONSTRATION PROJECTS
Several JVAH sites used innovative approaches to foundation construction that reduced costs while maintaining structural integrity. In some cases it was necessary to provide results of soil bearing tests and engineering data to the city building department. In every case, less costly foundations resulted.
Crawl space foundations in Christian County typically are built of one course of 12x8x16 block and two courses of 8x8x16 block. The 12-inch block serves as a brick ledger. The builder, Norris "Pup" Robertson, used three courses of 8x8x16 block stacked without mortar and bound together with glass fiber reinforced surface
bonding cement. This reduced the concrete footing from 20 to 16 inches wide and eliminated 16 inches of brick veneer.
Cost savings amounted to $203 per unit for the footing and foundation, and $410 per unit in brick for a total savings of $613 per unit.
The typical Santa Fe single family home foundation consists of an 8×16 concrete spread footing and an 8-inch thick, 22-inch high cast-in-place foundation wall.
Mike Chapman, builder, decided to build a thickened-edge, monolithic slab which is common in some areas but not in Santa Fe. This allowed a one-step operation instead of three steps and saved two days of construction time. Cost savings amounted to $106 per unit.
Typically, Tulsa single family homes are built with concrete slab-on-grade foundation/floors. Crawl space homes with wood floors are rare and usually more expensive. Wayne Hood, builder, decided to build a system unique to Tulsa – the underfloor plenum system on a pressure treated wood foundation.
Instead of using heating and cooling ducts, the entire underfloor space is used as a sealed plenum chamber. Basically, it consists of wood floor construction with sealed and insulated foundation walls. In the Tulsa JVAH homes, the underfloor area was used as a return air plenum with a conventional up-flow furnace. In most cases, the underfloor area is used as a supply plenum without duct work.
Information on the system can be obtained from the American Plywood Association, the National Forest Products Association, the Southern Forest Products Association, and the Western Wood Products Association.
It is being marketed under the name Plenwood.
According to Hood, cost savings amounted to $ 1,470 per unit versus conventional slab-on-grade foundations with overhead heating/cooling ducts.
Knoell Homes conducted soil bearing tests on the site and found the soil had a bearing capacity of over 3,000 psi. Because of this and because of minimal disturbance to the soil, Knoell received a waiver to reduce slab thickness from 3 1/2 to 2 1/2 inches and to eliminate fill under exterior concrete. Savings amounted to $195 per unit.
Gary Minchew eliminated reinforcing rods from footings and welded wire mesh from the slab. In addition, he eliminated a metal "key – way" control joint down the center of each slab, saving $132 per unit in labor and materials.
Rex Rogers reduced concrete slab – on-grade thicknesses from a nominal 4 inches to a nominal 3 inches, and reduced concrete strength from 2,500 psi to 2,000 psi, saving $160 per unit.
Pressure treated wood basement foundations were used in all Fairbanks JVAH homes. Tom Webb had been building wood foundations for several years and found no sales resistance. Because of the high concrete costs in Fairbanks, the wood foundation was especially attractive. It also allowed Webb to extend the building season which was very important in Fairbanks. Cost savings amounted to $1,035 per unit.
Karl Witt used pressure treated wood foundations in two units but was reluctant to build more because he anticipated negative market reaction. None occurred.