Permanent wood foundation
Hello,
Looking to build another house for myself. I own a residential framing company and have many years of experience in framing and in the building industry. I have been tossing around the idea of doing a permanent wood foundation. I plan on finishing the majority of my basement (roughly 2000 sq ft) and the insulating value of a either 2×8 or 2×10 wall would be a minimum of r 30 cavity and then whatever thickness (R10 most likely) of XPS I choose to put on the exterior of it. Totaling out at R40 basement wall. In the cavity I would spray 2″ of closed cell foam and then fill with blown cellulose or blown fiberglass. Figuring the 2″ of closed cell would lock out any moisture. I just see this being a great warm well insulated wall that I would build myself than rather pay my poured wall sub contractor $40-50k for his material and labor and then still have to build a stud wall on the inside perimeter to insulate.
I would do this system right with a peel and stick waterproof system possibly with a dimple matt and then do a full backfill with stone to get the correct drainage around the wall and get water away fast.
No one around me does ICF so I am not considering that. Prefer to work with wood being that is what I do for a living and have the tools and equipment for it already.
So knowing that wood basements are not very popular just looking for anyone opinion and suggestions. More or less would like to know if I am crazy or not for even considering this.
Thanks in advance!!
-Mike
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Replies
I have serious doubts about the long term reliability of wood foundations, and if the foundation fails, so does the rest of the structure. You can relatively easily repair any part of the structure EXCEPT for the foundation, so, in my opinion, the foundation is NOT the place to try to save money.
If I was going to build with a wood foundation I’d use poles for framing and end up essentially with a slab on grade with somewhat beefier wall support. If I was building a “regular” home, I would only use masonry below ground. I just don’t trust wood there regardless of the treatment used, and foundation problems are a nightmare to deal with down the road.
Those are my two cents anyway :-)
Bill
I've have been very interested in PWF but have the same reservations as Bill. The question is what will happen a couple of decades down the road.
Water proofing technology has come a long ways, so I can see that a properly detailed one should work but it still makes me nervous.
I think for DIY, your best be is still either ICF or CMU. Maybe try to pick a hilly site where there would be much less bellow ground, you can then frame a lot of the basement walls in wood for the above ground sections.
P.S. Spray foam is something you always design OUT in new build. There are much better, cheaper and more environmentally friendly ways to air seal a house.
I remember being surprised to read that there are underground foundation SIPS available. I thought I was reading it wrong.
I also feel weird about wood underground. I'd actually go further to say the risk isn't worth the savings. Or maybe it is... Depends much you're saving I guess.
Consider doing the concrete foundation yourself. It's not rocket surgery.
Well respected builder (and all around really nice guy) Mike Guertin recently posted about a 30 year old permanent wood foundation he did that's still going strong: https://www.instagram.com/p/B-wjiQmDTX5/
In the comments, he also says: "I built 4 PWFs from 85-89 and all are still fine. [...] Planning to build my next house with PWFs as part of a FPSF."
Lots of folks DIY ICF foundations.
Some thoughts.
If its designed right and has a dimple mat to separate the wall from the soil it should work great. My inlaws have one but its newer from the early 2000’s. My father in laws brother has one from the early 80’s that is doing well, north central MN has quite a few. My neighbor told me this spring one collapsed somewhere nearby, Im assuming from rot. I was going to ask who and where to ask the owner about it, but this stay in place stuff put a lid on that plan.
I considered one for my own home but didn't want that amount of treated product exposed to the indoor environment.
I wouldnt do CMU unless you were in straight sugar sand, I have seen so many cracked CMU basements during remods, usually buckled halfway up horizontally.
There is a WI company, not sure if they are still in business, that was building foam core fiberglass type panels you could buy and assemble yourself with studs molded into them. Concept was cool, did 2 houses with them, but price was very high. Edit: name is Epitome.
Bigger question, where do you live paying 40-50k for poured wall? I pay around $60 LF for 8’ poured.
> Bigger question, where do you live paying 40-50k for poured wall? I pay around $60 LF for 8’ poured.
I know in NJ, a poured wall for my small addition was cost prohibitive. Approximately $40K for 60 linear feet including excavation and slab for about 250 ft^2 of basement area.
I did my take off on it this morning. For 306' of 9' tall x 8" poured wall and 229' of 4' tall x 6" wall was $33k. This is my price in Michigan. Still need to insulate it but that is with waterproofing.
For that amount of footage I wouldn't be that much less, must be a big garage and some walkout with all the 4’?