I have a wood foundation built in 2001. It looks like he just put poly around the outside and nothing else and now the poly has fallen apart above grade and I don't think this is a good thing. I have been trying to find out what all needs to be put into a wood foundation and have not found any clear answers. Obviously you need a vapor barrier around the foundation below grade no questions there and in that respect I am probably good to go. But I have seen diagrams where the plastic stops when it reaches above grade and some that the plastic goes all the way to the siding, some also have plywood on the outside of the plastic but I cant tell if it is supposed to go all the way to the bottom of the foundation or just below grade up till the siding to protect the poly. Hopefully someone can point me in the right direction. Thanks.
Wood foundations are widely used in western Canada. The Saskatchewan government has issued a brochure on the requirements for these.
Here's a link! http://www.cpsp.gov.sk.ca/pwfbrochure.pdf
Quote< Exterior Moisture Barrier
Except for knee walls or crawl spaces with
trenched footings, the below-grade portion
of the exterior face of a PWF enclosing
habitable space must be protected by a 6 mil
polyethylene moisture barrier. It must be
applied to the plywood by embedment into
vertical beads of sealant or into uniformly
applied dampproofing. The moisture barrier
must cover the entire surface of the wall
below grade including a wood footing, but
cannot extend over the granular drainage
layer, under a wood footing, or obstruct the
drainage passages in a concrete footing.
The moisture barrier must be protected at the
upper edge and at corners. At the upper
edge, 150 mm of the moisture barrier must
be looped over a 12.5 mm thick by 300 mm
deep cover plate of treated plywood. The top
of the cover plate must extend at least 75
mm above grade at any point, and be
embedded in sealant or dampproofing
I think I understand. From what I read the plastic must run at least 3 inches above grade at all points. When it gets there it must wrap back down 6 inches around a 12 inch piece of plywood that is a 1/2" thick. Sound about right and then sealed at the top. So basically it needs to wrap around a second piece of plywood and back into the ground. Sound about right?
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