A permanent wood foundation (PWF) is a system which utilizes preservative-treated lumber (a process where the wood is pressure-infused with chemicals to resist infestation and decay) instead of the traditional methods of using masonry products or solid concrete.
There are a few benefits/advantages to wood foundations.
PWF’s are not constructed in my area, therefore I have not be able to inspect one after 10-20 years to determine their longevity and any issues they may encounter.
However, I do have a couple of concerns with PWF’s.
First: The waterproofing of the foundation. In my area, about 90% of basements and crawlspaces have some water intrusion with 10-20% of those having serious water issues. If water were able to penetrate a PWF wall, then it will rot over time and cause fungus growth inside the wall. Many people have the misconception that preservative-treated wood will not rot. This is just not true. Over the years, I have found it rotted many, many times. It just takes longer to rot than regular wood. And yes, there are different levels of preservative-treated wood and the higher concentration wood will be more resistant to moisture for a longer period of time, however it can still rot. And repairing a leaking foundation is very expensive.
While moisture intrusion on a masonry foundation wall is also bad, it does not deteriorate the wall itself, the structure holding up the weight of your entire home.
Second: Wood destroying Insects. While preservative-treated wood is resistant to wood destroying insects, such as termites, it is not impervious to them. Over time, it loses it effect on repelling these insects. Once again, over the years, I have found termites in preservative-treated wood many times. And the closer the wood is to the ground, the more likely it is to attract wood destroying insects.
When you are building your home to last forever, I would prefer to trust the time tested masonry foundations over a wood foundation any day. There are thousands of masonry structures all over the world that have lasted for hundreds of years and are still in excellent condition today.