PWF "Permanent" or "Powdered" Wood Foundation?

I’ve only inspected two of these and stuck a screwdriver right through the treated plywood in both homes. Ever inspect any of these over 20 years old that were good?


I never even heard of the term “Powdered Wood” foundation…you have any pic’s.

“Powdered” is a reference to their condition after 20 years of being considered “permanent.” :wink:

…:lol:…oh lord…:cool:…Good one JP…:lol:

I want to see Kentons pic’s of a Powdered Permanent—I have never seen one of those either…:lol:

What is it?..a plywood basement wall system?..or stem wall?..I don’t think Kenton mentioned basement…but I’m taking a wild guess…:-&
I have inspected too many and do not have much love for them .
Did Four recently two the bought two walked away.

… Cookie

Thanks Roy…I have never seen one…heard of them, that’s it.

Anyone have any pictures of a bad one they inspected?

In most cases you have no idea they are wood as the ones I looked at you seldome get to see any foundation .
.The out side was covered with cement Board to below the ground and inside are completly finished . Usually warm and dry.
… Cookie

Imagine that…getting my $289.00 worth everyday it seems…!!!

Dale, this may help you out here on pictures.

Permanent Wood Foundation Pictures Of Common Construction Details.

1.Lumber and plywood treated to .60 and stamp with a (FDN) foundation grade stamp.2.Wood poles treated to foundation grade lumber requirements.3.9 ft basement with the wood basement floor system and a wood garage foundation.4.It easy to dig a hole for a wood foundation.5.Step 1. stake out the size of the basement and add 1 ft. for the over dig. (each side)6.Dig hole 1 ft. over dig and down to proper depth.7.Note the deeper dig around the outer perimeter use as the graver footing system.8.The porch area can be completely excavated out.9.Corner view of a 12" over dig hole in a clay soil site.10.Dig out for point loads for wood gravel pads or concrete pads.11.Ready for graver to be dump in the hole.12.Dump stone in all corners.13.Have the back hole move the stone.14.Stone fill to walls of over dig.15.If soil is less than 1500 lb. per sq. ft. Have soil tested.16.Clean out any fill that drop in trench, before adding gravel.17.Use 4" of graver under floor area, 6" deep at wet sites, like wet sand sites.18.All lumber and plywood required to be treated must be stamp foundation grade.19.Install all load pads under footing plate in the gravel fill.20.Level graver under wall location with leveling board made as site.21.Install footing plate and layout in a clock wise direction. Dip all lumber cuts.22.Start at a corner and work in a clock wise direction.23.Any studs that are cut can be installed with the cut side up, you do not have to dip cuts.24.Plywood goes past the end of wall, and cover the end of the next wall stud.25.The next framed wall panel is installed in place. 26.Windows are easy to frame but will required more support than upstairs framing.27.Caulk all plywood to plywood seams, do not caulk other joints in framing.28.Blocking at the plywood seams may be required by design.29.Day light walk out walls are required to be treated lumber and plywood (see design).30.Blocking in some walls are use for shear walls support.31.Some wall designs require plywood on two side of wall. (shear wall design)32.All basements require a sump crock, can be made of treated materials. (no bottom)33.Plywood support pad installed under all point loads that over load the footing plate.34.Wider footing plate use to support brick knee wall installed after wall poly.35.All ways pour concrete floor up on wall studs as required by design. (1" min.)36.Wood basement floors are warm and dry, they are easy to install and go in fast.

Marcel :slight_smile:

Great Pictures thanks Marcel,
Have you ever built one and do you have an opinion on them .


Have built, worked with or around 15+ PWF’s since 1980. Actually just mentioned on another thread a few days ago that these were my favourite foundation.

Last one I supervised/worked on was for a former employee/friend in 2000. We had his large 1882 house excavated/blocked in place by a housemover and then built the PWF under the dwelling…took a full 7 days for 4 of us…but the house had 18 inside/outside corners to frame under, not counting 3 on an attached but unexcavated shed. This was in heavy clay soils and he has had no problems as of yet.

The oldest PWF in that area of New Brunswick is now 30 years old and has had no problems. I check in with the owners every 5-6 years or so to enquire about it.

I built a new home for a client on a lake in 1987. The wood foundation has had no problems that I know of. A minor water entry problem developed when through a couple of of reinforcing changes made by (1) the second owner- putting in a new submersible sump pump for its quietness while inadvertently raising the water level in the sump pit- and (2) an excavation contractor- he raised the drainage and general water table level in the area while preparing his own site for building!! This also killed a number of 30-40-50 year old trees with water covering the root systems!! The water problem was easily solved in the end.

If PWF’s are built to widely recognized standards, there should be no or minor problems only. Owners consider them to be dryer and warmer than concrete foundations. If built without concrete footings directly on local soil but with a wood footing plate on a minimum 5" compacted gravel base, a foundation perimeter drain tile is not needed. The CSA standard for them here has been made less stringent over the years as they are performing admirably and better than expected.

I would check out the certifying agency, standards, etc for the preservative treatment…sounds like somethings amiss there.

Quote from a PWF site (forget its origin): “Wood foundations originated in 1938, following the development of preservative-treated lumber and plywood designed to resist decay from moisture and infestation from insects. To date, over 300,000 homes in the U.S. have been constructed with wood foundation systems.”

A great reference manual is found at this site:

Brian, I have to agree with you having built 18 of them myself. If they are done properly they should never “see” any water. I think one of the common misconceptions is that the wood is the kind you go down to **the orange tool box **to buy.

The only two I’ve inspected were hidden behind int. wall coverings, Dale. I dug down a foot or so and stuck a screwdriver through each.

Bad grading is the rule rather than the exception in homes around here, so building (or buying) a home with a foundation which basically disolves (decays) when exposed to moisture over the long term seems like a really bad idea.

These homes were both 30+ years, plywood was green. I imagine a lot of the problem is the fact that they need to be built to certain standards and builders in the past haven’t bothered to find out about standards or what’s important in building these types of foundation walls.

I’ve only seen wooden foundations twice. Both times, the foundation resembled rail-road ties - size and shape - staggered and stacked two high with vertical through-bolts. Both times, they had significant infestation (rot & insects) and were on Desert homes.

I know of no CA jurisdiction that allows this type of foundation for “habitable” spaces.

I agree with Charles, having built many of them myself.

Properly constructed, they are fine in our area.

Nice links and pics Marcel and Brian.

If not built with pressure-treated plywood that is treated to a much greater preservative content that normal pressure-treated plywood, I guess one could stick a screwdriver through them after 30 years…or even less. One cannot take any old pressure-treated plywood and bury it…it needs a much greater preservative content, and usually must be specially ordered, except perhaps in the south, where such foundations are more prevalent.

This was found through TIJ

PWF Design & Construction Guide
Design specifications and structural requirements for using PWF systems. Typical applications are illustrated. 52 pages.
PDF Download Only Ref #400.

$0.00 each.
[Download FREE](

More info on Southern pine

Good one , Barry. And the price is right…oops, my Scottish genes are showing. After working on PWF’s many years ago, almost became nostalgic looking through the details!

One of the two I looked at appeared to have failed during backfill. Main floor framing was typical western platform and the floor joists rested on the PWF walls and was toenailed to top plates. The top plate had buckled at one of the breaks. The wall was bowed in at this point about 3 inches over 30’.

Finished basement with lots of interior walls and suspended accoustic tile ceiling. Easy to miss. Repair involved backhoe excavation and was expensive.

Given that many contractors seem to be unable to build capably using long-established, well known methods, I’m skeptical of this system as being unforgiving of mistakes and possibly requiring replacement of the entire foundation structure (or a major part of it) if poorly built. It’s builders who don’t do their homework that worry me.