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

19 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
    • Ter

      Marie, your own experiences are as norma and personal to your situation and in accordance with all of the factors you have indicated. Here, local Municipal Inspectors are not qualified nor expected to carry write-off authority on the construction of PWF’s, that responsibility falls to CMHC for the very reason(s) you allude to as to qualifications. However, there is considerable concern(s) when a buyer is in consideration of a PWF home purchase as to finding a qualified Home Inspector. As all builders do not construct them, and know very little about them it stands to reason HI’s are also as an industry not conversant in the techniques. That is further true if you recognize the percentage of PWF homes is dwarfed by either block or concrete applications they predominantly are confronted with. And at times are also limited in their experiences with them as well. Seeking out a qualified HI with background experience in both the technical and construction elementals of PWF’s is like finding a needle in a haystack, but we are out there minus a bag full of fed flags and recommendations because we can articulate the realities of this type of construction. having said all of this, there are other construction methods which can contribute to the problems you have mentioned aside from just foundational. Understanding, any structure begins at a good foundation, but also requires many other important structural elements to it’s envelope. Undersized window/door headers, fact that homes generally do not find their final settlement within an 8 to ten year span can and will cause drywall concerns, truss uplift is a major culprit for example. it is difficult at best to determine the root cause as the PWF in and of itself simply from a visual inspection, albiet, not completely impossible if a good HI knows what story the rest of the structure is telling and whether they are solely to be attributed to the foundation itself. And, yes, PWF’s are dependent on proper installation from the start, no differently than are block or concrete.

      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
      • Brian

        I bought a home with a wood foundation, it was built in 2002 in southeast Michigan. I have noticed 2 walls bowing pretty bad. How do I fix this? Does it need to be fixed?

        Reply
        • Nordic Home Inspection

          Brian, it is impossible to answer that question without actually looking at the foundation. If you have two walls that bowing “pretty bad”, it sounds like something needs to be done. This typically involves excavating around those walls to bring the studs and the wall structure back out. I suggest contacting your local foundation repair contractor or a structural engineer for further evaluation and to get recommendations. If the walls are bowing “pretty bad” chances are that you have to repair the walls when you sell the home anyway.

          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
    • Ter

      Eric, rest easy, and head towards retirement with a sense of control. I have been constructing PWF’s for 40 years, Inspecting them for realtors buyers for much of that time. You have made as wise a decision as anyone who refuses to look at PWF’s and only swear by block or concrete, both of which I also have much experience installing and history repairing as opposed to virtually never having to even look at a well installed PWF system for correction’s. Drainage is your number one priority. And, as to no drain perimeter drain tile, that is proper install application. Happy to elaborate on that should you wish.

      Reply
  7. Larry Schimmel

    My PWF basement has a leak and we need someone in Southeast Michigan to take a look at it for repair. Do you know of any foundation repair company’s that work on PWF?

    Reply
  8. Jim Young

    I was in the trades for most of my life. I worked for years for my uncle who was a contractor. He built a lot of FHA loan homes and most were wood once it took off in the late 80s. This was mostly because it took the better part of a week to get a concrete basement up and he could put up a wood one in a day. My dad talked me into doing a wood basement on one of my homes built in 95. I over did it because I was never sure of the process. It is counter-intuitive. So I went 2×8 1 foot centers, with 5/8s ply all triple treated, I did not use the pea stone footings but poured a cement footings and then used a 2×4 with nails in it to rake lines for drainage. As a floor plate I used a 2×12. After that I used heavy mil plastic after coating the outside with tar. Also a french drain in pea stone going to daylight and the soil was beach sand. I sold that home 2007 and it was the driest basement I ever had. I had insulated it and dry walled it never had any mold or issues. How long will it last? I have no idea. But I gave up on them because of one thing, I have seen a lot of old home sites over 100 years or more and one thing that stands out is the concrete foundation is still there. The other issue that would detour me from using wood as a foundation is resale. My wood basement home was dry walled on the inside complete and on the outside I covered any exposed part with tar-paper and wire lath and scratch coated it and cultured stone. So you could not tell it was wood. I wondered if one day it would be, the fumes from the treated wood, or rot or something made it not salable. Masonry is not ever going to be an issue. The next home I built was 8 inch block poured cores with seal then tar and membrane draining with french tile. 2×4 interior walls dry-walled and it was fine.

    Reply
  9. Matt M.

    We have a wood foundation that was built in 1992. The builder and former owner is actually our neighbor so whenever I have problems I can just go to him. He did an excellent job on it. The overhangs and gutters on the roof are enough that we don’t have to worry about water getting in. It’s also built up on a hill with a lot of sand under and around it for drainage. That is a key part of being able to maintain it from my understanding. It spooked away a couple buyers before us but it’s been a phenomenal home for us and our growing family. We’ll built and well insulated for Minnesota winters. It’s a very dry crawl space and It’s always about room temperature so I’m able to go down year round in my t-shirt and have access to plumbing, HVAC, etc. I don’t understand why people are so frightened by a wood crawl space. Hopefully that doesn’t affect our re-sale down the line.

    Reply
    • Nordic Home Inspection

      Matt,
      I agree. A wood foundation is a good option as long as it is properly built and the drainage around the home is good. We rarely find any problems with homes that have a conditioned crawlspace so that shouldn’t alone be a reason for someone to not buy your home.

      Reply
  10. Melissa Marrero

    I live in Alaska, would that be an ideal area for wood foundation? There is a house I want to buy but am nervous just because of the wood post foundation..

    Reply
    • Nordic Home Inspection

      Melissa,
      It is nearly impossible to answer that question without inspecting the home, but generally I wouldn’t have a any concerns buying a home with a wood foundation as long as it is correctly built and properly maintained.
      I would highly recommend you to hire a certified home inspector with experience inspecting wood foundations prior to your purchase.

      Reply

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