Permanent Wood Foundations
jollygreenshortguy
| Posted in Green Building Techniques on
The IRC has provisions for “permanent wood foundations”. I have no experience with them and welcome your insights.
In all my career I’ve never seen these used on a house. Why not?
It seems a great opportunity to eliminate a substantial amount of CO2 from our construction process. What are the downsides?
What are your experiences with them?
What are their limitations?
What soil conditions are they suitable for and unsuitable for?
If properly designed in a suitable soil, can they be expected to provide at least 100 years of good service?
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Replies
JGSG,
This BS & Beer show has a lot in interesting insights: https://www.greenbuildingadvisor.com/article/the-bs-beer-show-permanent-wood-foundations-pwfs
You may also find the two articles useful:
https://www.greenbuildingadvisor.com/article/water-and-a-permanent-wood-foundation
https://www.greenbuildingadvisor.com/article/planning-for-a-permanent-wood-foundation
I don't have any experience designing them on an actual project, but I have gone down the wood foundation research rabbit hole before. One more article to add to Malcolm's reading list: https://buildingscience.com/documents/building-science-insights-newsletters/bsi-020-wood-foundations-picasso-does-foundations
Malcolm and Brendan, thank you for the resources.
We have many houses in my community built with PWF, this was a popular style in the 80s and 90s. Done correctly, they perform very well and provide for a good home.
However, any house for sale with a PWF is given a lesser value and is less sell-able. This is because these foundations do have a shelf life (especially with our poorly drained soils) and they will need to be replaced at some point. Every year there are several local houses lifted and wood foundation replaced with concrete.
FHB also covered this recently in their podcast aftershow, here's a link if you are a subscriber:
https://www.finehomebuilding.com/2023/05/19/podcast-541-members-only-aftershow-permanent-wood-foundations
Recently, hundreds of the worlds top scientists gathered and stated that the 3 most dangerous things to cause the extinction of the human race are nuclear war, global pandemic and Artificial Intelligence. Nowhere did I see concrete on the list. There are bigger things to be worried about than trying to save some concrete and use PWF as an alternative to help "save" the world ;) The human race will most likely meets its demise from one of the above mentioned scenarios, not global warming or pollution. History has shown that violence and disease kills the most humans. Now with AI in the mix, it's pretty much a done deal.
So pour your concrete, have a drink and enjoy your time with friends and family...
jackofalltrades777,
...and pets.
Of course, our pets: ) After COVID19, I no longer sweat the small stuff. I do my part and try to build energy efficient and durable structures. Human history is a good indicator of where we are headed . Like I said, history has shown that violence and disease kills the most humans. While global warming/pollution is a concern, it is not as dire as some claim it is. Human extinction will not come from global warming, it will come from either a nuclear war, a global pandemic and/or Artificial Intelligence. Maybe all three but using concrete for a foundation is not going to cause human extinction.
A study came out that shows that in order to produce an EV vs an ICE, it takes double the amount of carbon emissions than an internal combustion engine car. To offset that it will take 100,000 miles of driving in the EV, with the original battery. Some will argue against that but the reality is not everything is as black and white and their are hidden agenda's with some of these "green" ideas and people are getting rich on it while fleecing the public under the guise of "green".
I question some of those studies showing an EV being so much worse (enviornmentally) to produce compared to an ICE. I remember when the Chevy Volt came out, there were people saying it was such a money loser because the cost per vehicle was so high, but even GM was saying the Volt was something of a technology demostrator and test platform, so much of the R+D cost people were rolling into the per-vehicle cost to build a volt was really stuff that would be used for future models too. R+D costs didn't mean EV's were impractical, it just meant that things wouldn't be provitable right from day one, which was expected, and is the case for pretty much anything new.
My concern with the viability of EVs on a large scale is the simple reality of where the energy is going to come from to charge them all, since there simply isn't enough generation, or transmission, to support a large scale conversion. Capacity margins are already very tight on the grid in general, and that's only getting worse going into the future. No one seems to want to talk about that, or any realistic solutions to the problem.
I do agree people tend to use "it's Green!" to "justify" a lot of things that don't make sense, which is unfortunate. More often though, I see people look at only one piece of a large system, and then they may make that one piece good, but the entire system ends up being worse, so they end up being less "green" than they would have been if they'd thought about the entire system instead of any one part of it. The goal should always be the best *overall* system, not a crummy system with one really nice piece. It's like taking a rusted out car that belchs smoke and barely runs, but saying it's great because you replaced one lugnut on one wheel with a shiny new part.
Regarding the OP's question though, I am not a fan of wood foundations, because the "permanent" part is very much in doubt. If the foundation fails, you have a VERY expensive repair that compromises the entire rest of the structure, and if you rebuild, you've more than canceled out any carbon savings (or any other savings) you might have initially had using wood for the foundation. I will only use masonry foundations on any of my projects.
Bill
Is the UC4-B rated pressure treated lumber, required for PWF commonly available? I have casually looked for it in the Northeast via the web and came up short. Maybe it takes a phone call to the lumber yard to special order? All anybody has is the ground contact PT, not ground burial PT.
Our Canadian standard for preserved wood foundation has the use class as "ground contact in severe environments". I would assume that you could find a lumber yard that will source the correct materials for you, perhaps as a special order.
The wood preservatives used in these applications are particularly nasty, and I would suggest wearing gloves and a mask while working this type of wood.
I agree with the above comment that "permanent" is the wrong word to use for this system.