When most people think of Canada, they think of hockey, maple syrup, and free healthcare. Another thing that Canada is known for is how they build foundations. In the United States, most residential and light commercial foundations are made of either poured concrete or concrete masonry units. However, in Canada they often use wood to construct them. These foundation types are called PWF (Permanent Wood Foundations).
There are many advantages of using wood as a foundation material over concrete. As basements can account for up to 37% of the heat loss within a home, making them energy efficient is critical. The combination of wood's low thermal conductivity with the addition of insulation can provide long-term energy savings.
Construction time is an important factor when considering cost effectiveness. A PWF takes one-third to one-sixth less time to construct than a concrete foundation. It is also easier to build, omits the labor cost for a concrete contractor, and eliminates the possibility of construction delays between crews. The same crew hired to frame the house also constructs the foundation and basement. However, the means and methods of a PWF will likely be unfamiliar to most framing contractors in U.S. which may add additional time for planning. Another advantage of PWF over concrete is the ability to be built in cold weather conditions. The construction season can extend year round, preventing potential costly delays associated with other concrete foundation systems. Ideally, the most favorable temperature for concrete is between 50 - 70 degrees Fahrenheit. With the use of an admixture to resist freezing, incorporating an additional heat source, or temporarily enclosing concrete sections can allow it to be used in cold weather.
Structurally, wood is much lighter than concrete, so a PWF can be placed on a bed of gravel rather than a typical concrete footing. Wood is also more elastic than concrete which makes the foundation less susceptible to cracking and moisture penetration. Wood is also vulnerable to a variety of natural and manufactured defects that can affect its strength and use. In addition to these defects, wood can also be damaged by fire, insects, and fungus.
As demand for sustainable building practices continues to increase, wood is in many ways much more environmentally-friendly than concrete. It requires far less embodied energy to produce, has a low carbon footprint, and is a renewable resource. As a foundation building material, wood and concrete have their own advantages and disadvantages and a careful analysis of cost, time, and sustainability will need to be taken into account for a best practices solution.