Wood for a Home Foundation?
We all know a home's foundation needs to be solid, strong and if not permanent at least able to last for years. Traditionally the materials of choice for home foundations was some form of stone, cinder block or poured concrete that are obviously strong and long lasting. However in recent years home foundations made from pressure treated wood have been gaining popularity. If you're wondering about wood foundations here's a quick overview of how they work and some of their advantages and possible disadvantages.
Do wood foundations really work?
- More than 300,000 homes have been built in the United States with wood foundations and they're not really a new idea. Wooden foundations were first built in the 1960's shortly after the development of preservatives for wood that prevented rotting and insect damage.
- Regional building codes have accepted wooden foundations since that time and in the year the 2000 International Residential Building Code (which applies in all areas of the US) incorporated wooden foundations as acceptable for residential home construction.
- In addition, the majority of insurance companies and mortgage lenders willingly accept homes built with wood foundations so they're comfortable with the concept of wooden foundations.
How do you build a wood foundation?
- Wood foundations are much easier and less time consuming to build than traditional concrete foundations. First, the foundation hole is excavated then a layer of gravel or coarse sand is laid down and leveled. Foundation walls can then be site framed (similar to a homes exterior walls and by the same crew), using 2 x 8” studs on 16” centers and sheathed with 1/2” or 5/8” treated plywood. A layer of 6 mil plastic is placed over the exterior of the walls before back filling to protect from moisture intrusion. Alternatively, pre-built panel foundation systems can be used to build the foundation's exterior walls.
- Since the wooden foundation walls are much lighter than concrete foundation walls, there is no need excavate and pour concrete footings to hold the weight of the walls. As a result, building the foundation can be done in virtually any weather and there is no need to wait for the concrete footings to dry.
What are some advantages of a wood foundation?
- In addition to being easier and quicker to build than traditional concrete foundations, wood is more elastic than concrete, minimizing the threat a concrete wall will crack and allow water into the basement.
- In addition, wood has better thermal properties that concrete or stone, so a basement with wooden walls will be warmer. As well, since the walls are already framed with wood, adding extra insulation between the studs, running wires or plumbing pipes through the studs is much simpler and significantly less expensive.
- According to the www.woodfoundations.com, a properly constructed wooden home foundation will last for 100 years, but to date there aren't any wood foundations that old.
- Some people are concerned about the chemicals used to preserve wood. One of the original chemical Chromated Copper Arsenate (CCA) has been withdrawn from use in residential construction