Originally Posted By: kfulton
This post was automatically imported from our archived forum.
That did not work, I’ll try it again… This is off a web site I found when researching the last wood foundation I inspected. I have inspected three this year. If built right, they are warm and dry. If not built well… make sure you have a quality moisture meter, test and probe every thing.
Some people may be skeptical about the long-term durability or strength of wood foundations. However, accelerated aging tests, and use for over 40 years attest to the durability of this system. Permanent wood foundations for residences have been constructed for decades in the U. S.. Wood foundations resist cracking, and are easy to insulate and finish for additional interior living areas. Over 300,000 U.S. homes have been constructed with wood foundation systems.
Because wood foundations are significantly lighter than concrete or block walls, they may be placed on gravel beds, eliminating the need to cast and cure a concrete footing. A concrete slab may form the floor within the foundation, but most manufacturers promote the use of a treated wood floor system. Manufacturers state that wood foundations are also more thermally efficient and elastic, therefore less subject to cracking and moisture penetration.
Typically, walls are framed with 2x8 treated studs on 16" centers, or as specified by the designers. The exterior foundation surfaces are normally clad with ?" or 5/8" treated plywood, and polyethylene film is typically applied before backfilling. Following excavation, a base layer of gravel, coarse sand, or crushed stone is placed and leveled. Panelized foundation sections can then be set in place, or the foundation can be site framed as for conventional wood walls. Fasteners must be stainless steel or other corrosion resistant material. When wood floors are used, floor joists are placed on sleeper strips, directly on the aggregate bed. Wood joists also allow the incorporation of plumbing, wiring, and HVAC ductwork into the floor system, prior to the installation of treated floor sheathing. For basements finished as living space, the cavities of wood foundation framing are easily insulated with conventional batts or blown cellulose. Plumbing, wiring, and drywall are installed as for any framed wall.
Depending on the location and soil conditions, a sump pit, drain piping, and appropriate vapor barriers are recommended. Exterior plywood surfaces are typically covered with minimum 6 mil polyethylene prior to backfilling.
Permanent wood foundations are permitted by the 2000 International Residential Code (IRC), which specifies fasteners, wood treatment, and gravel or crushed stone footings. Wood foundations are also accepted by most lenders and insurance companies. Codes often refer to American Wood Preservers Association (AWPA) standards. They require certain species of Pine or Fir, limited to 20% heartwood, treated to 0.6 preservative retention (compared to 0.25 to 0.4 for regular treated wood), kiln-dried, and stamped by the treater. The four treatment methods previously approved by AWPA are CCA, ACZA, ACQ Type B, and ACA. However, the Environmental Protection Agency will not permit CCA for residential use after 2003. Check with local code offices to determine the requirements in your area.
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