Preserved wood foundations are few and far between in common buildings today. However, these foundations can last just as long as a poured concrete foundation if they are built and prepared correctly.
The wood used is treated with mold and water-resistant chemicals, just like deck building materials or any wood product that is formulated for outdoor projects. The walls are framed as a typical wall would be except with 2×8 wall studs instead of 2×6 wall studs. The exterior sheathing is made of 3/4 inch treated plywood and installed like normal sheeting on the house. 2×4 blocks are installed about mid-wall across all the walls that will be covered with soil. This helps maintain stability while backfilling.
Because wood is so susceptible to moisture damage, every inch of the wood exterior must be waterproofed. A special membrane adheres to the walls. It is impermeable to water and allows a drainage plain to be installed over the product. The drainage plain is dimpled and allows water to pass through it against the foundation to prevent freezing water from damaging the foundation. The drainage plain material is tied directly to the drain tile around the perimeter of the house to avoid puddling at the footings.
The foam board insulation is then applied and tared over to prevent moisture through the board’s seams.
The backfill around the first 2 feet around the entire foundation is 3/4″ clear stone. This allows water to drain freely to the drain tile system. Regular soil is used for top grading, and all areas by the house are pitched away from the home to promote positive drainage.
Preserved wood foundations are very warm and do not have the cold transference that concrete does. This is because wood is a poorly conductive material and does not conduct heat or cold like concrete, making it very efficient.
Because it is a wood foundation, the chance for wood rot and insect infestation are going to be possible. If a corruption occurs by the footing, fixing the wood walls can be very time consuming and expensive.
If you’re interested in expanding your knowledge about the preserved foundation, consider joining an online support group like Woodworker’s Guild of America (WWGOA), which has more in-depth information wood foundations, plus other expert woodworking tips, plans, and videos. Read WWGOA reviews to know more about them.