Wood foundation, a disaster waiting to happen?

I feel sorry for the wood foundation. Not because it’s terribly unsound – because it’s not. Not because it’s known to settle or have chronic moisture problems, because that’s not true either. I am not sure where it’s coming from, but we commonly hear concerns about the wood foundation from home buyers. I have even seen home buyers walk away from the purchase when I made them realize it was a wood foundation and not a poured concrete foundation as they thought it was.

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“I can honestly say that I have seen less than five failed foundations built with wood. What’s common with all of them have been excessive negative grade over several years”

In case you didn’t know; accelerated laboratory testing of modern pressure treated materials indicates a lifetime of over 100 years with no serious deterioration, and the durability of the systems has been amply demonstrated over the long-term by in-ground tests conducted over the past 40 years by various Federal agencies.

 

A 100 year life expectancy or not, I have personally inspected thousands and thousands of homes – several hundred of them with a wood foundation. So let me share some facts based on my experience:

  • A block foundation is much weaker, and fails at a much higher rate in our area than a wood foundation
  • A poured concrete foundation will crack from settling or pressure from the soil, and it’s common to see water leaking through these cracks. Poured foundations also commonly start leaning due to pressure from the soil
  • It is very important to keep water away from any foundation, not only to prevent from moisture intrusions in the basement, but also to take pressure from your foundation. You do that by having a positive slope away from the foundation (dirt, concrete slabs etc. should slope away from the foundation wall – NOT towards it)
  • I can honestly say that I have seen less than five failed foundations built with wood. What’s common with all of them has been excessive negative grade over several years
  • We have no contractors in our area specializing in repairs on wood foundations. Simply because the demand is very low or not present

We don’t know exactly how long a wood foundation will last, but we know that the most common options to wood are poured concrete and concrete blocks, and I have seen those foundations fail in homes ranging from 10 to 50 years old.

My final conclusion is: wood foundations are probably not any worse than any other type of foundation as long as you keep the water draining away from the foundation

8 Responses to “Wood foundation, a disaster waiting to happen?”

  1. Marie

    Would not wooden foundations be dependent on proper installation from the start? How many city/county inspectors actually know what to look for as the wooden foundations are not that common? Who would you hire for a wood foundation home for a home inspection prior to purchasing? Your average home inspector I doubt has the skill set to know what to look for or even to look at. Wouldn’t the sub-soil for a wood foundation play a large factor? Water table? We have a wood foundation home, to say I am less than impressed is an understatement. And granted it may be the builder but I was skeptical about this home and had an inspection done by an engineer who said it all looked good. Twelve years later – heavy settling, cracks in the drywall, walk out flooring raising, windows out of alignment. I would say to endorse wood foundations should come with disclaimers, sub soil, water table, city/county inspectors knowledge, builders attention to detail and last but not least a home inspector that knows what they are looking at.

    Reply
  2. Duncan McLeod

    You’re probably right. If properly constructed and under the right conditions, PWF could be ideal and last as long, or longer than concrete. But as the owner of a home with a PWF that is failing, I believe it is important to acknowledge the additional risk associated with a PWF.

    Given that they are fairly rare, many homes with PWF were built by people with limited experience with building them, and so made more mistakes than you would expect with more conventional building techniques. Worse, once problems appear, good luck trying to find someone experienced with PWF repair. The costs skyrocket and replacement is the only sane option.

    Reply
  3. Clair Sorensen

    I just read your piece on wood foundations. I also put in a wood basement in my home in Detroit Lakes and think they are great. I am having a hard time finding information on wood foundations in the Dilworth area. We plan on building there and would like to put in a wood foundation but the inspector is not sure that would be a good idea, in fact he would a an engineer to approve and design it.
    Have you had an experience with wood founations in that area?

    Reply
    • Nordic Home Inspection

      Clair,
      I generally don’t have a big concern with wood foundations in our area as long as they are built correctly, and that the grade and guttering system is well maintained around the home. We rarely see failure of these types of foundations, but when we do, its typically related to an installation error, or the home owners failure to maintain the drainage around the home. I would make sure to hire a contractor that is familiar with how a wood foundation should be built though.
      If you have any further questions about this feel free to give us a call anytime!

      Reply
  4. Barb

    Our house is 13 years old and has a wood foundation. The wood is several placed – where the seams are – is coming apart so that there is a gap of about 2 inches where the 2 boards meet. Also some boards are warping at the seam. Is this common? Should we nail them in or let it alone? Thank you for any help! Moorhead, MN

    Reply
    • Nordic Home Inspection

      Barb,
      Warping, shrinking or deterioration of the exterior plywood is rarely a concern. A wood foundation that is properly built can fail from pressure from the soil due to improper drainage, but the signs from that is typically bowing of the wall which can be seen by looking along the wall from the exterior, or movement by windows.
      If you have any further questions about this feel free to give us a call anytime!

      Reply
  5. Randall Adams

    I live in Alberta and when my father retired in 1979 we moved to our farm and built a home with PWF on it. The drainage was good and we put some extra rock beneath to stabilize the foundation. The home only has a small amount of Concrete for the three Teleposts for the main beam in the center of the house. The basement floor was done with pressure treated wood also. There has been no water leaks of any sort and no movement.

    I would agree that if a builder knows what they are doing and ensuring the grade of the surrounding land is done correctly a PWF is a good building material and prospective owners shouldn’t run away.

    Feel free to ask your home inspector what experience they have had with PWF prior to engaging them for the inspection.

    Reply
  6. Eric

    My wife and I just bought a house with a PWF. It’s our first home, so to say I’m a little bit nervous is an understatement. The house was built in ’88 and is built on top of a sandy hill with a gradual slope down to a walk out basement. I would estimate approximately 60% of the foundation is below grade with maybe only 20% fully below grade.
    Reading the construction reports, there is no drain tile installed, and the foundation was coated with asphalt and covered over with poly as well. The logical side of me tells me that I’m in great shape, but something about having a wood foundation for a house that I may very well own for the next 60-65 years (I’m 25, and we’re considering making this our “forever” home) still makes me a little nervous.
    One area that is a concern is we have many trees around the house, so gutter care is a full time job. On one side of the house, if the gutters plug, the water drains into an area near the house where an egress window exits. To lower the grade for the window, an L-shaped retaining wall was created, and the water falls within the “L” which also happens to be under an extended porch, but still… grading the soil is difficult as I would be grading between the house and a vertical retaining wall which is maybe 4 feet from the exterior of the house. The grade within the retaining wall is roughly 4-5 feet above the footings. The grade outiside of the retaining wall is roughly 6-7 feet above the footings.
    Besides keeping the gutters clear, what advice would you have regarding the grade/landscaping of that area to protect it from potential water saturation?
    Of note – this area is also under a deck.

    Reply

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