Wood Foundations and Ground Water

[milkman636]

My wife and I have been in the market for a larger house for a while now. A nice one has come up for sale near us that has the bedroom space that we need and a nice parcel of ground, but it has a wood foundation. The basement floor would be at least 6' below grade at the front, and the grade tapers around toward the back of the house so it ends up being more of a daylight type basement somewhere around 4' below grade along the back. The basement walls are almost 100% drywalled and finished.

The house was built in 1997 and everything about the place looks like they didn't cut any corners. The materials, finish, and workmanship all look very good. The owners are the original ones that had it built. The husband died and the wife is selling it. The house sits way back about 1500' off the road in what used to be a farm field. The neighboring field is freshly tilled and is a typical loam soil. Grade is slightly sloped away from the house but then flattens out for 100's of feet around it. Its the type of setting where I would expect mud to be an issue in the spring.

The basement is dry with no visible signs of wetness and no musty smell at all. But it is also fall, not spring when its raining and the ground is thawing. I'm always concerned about groundwater, but because of unfamiliarity with wood foundations I am more concerned than normal. My wife wants to buy the place, but I need to know more about wood foundations. So does anyone out there have any insight for me on how they are constructed and what to look for?

I'm accustomed to our current home that is on the highest spot along our road, and our basement is bone dry and doesn't have a sump pump or even a crock for one. Am I being over-concerned about ground water issues?

 

[Sodo]

My home's foundation is wood posts, sitting on pierblocks. House is 87 years old and no problems with the wood foundation, its all straight. New half of the house is on a modern foundation.

Have a sump pump in a well below the basement floor, I actually have two pumps in there, one above the other, as a backup. I am on the highest spot in the neighborhood on a ridgetop. Land drops down in front and in back of the house and I'm a foot or so higher than either of my adjacent ridge neighbors. It's actually quite puzzling why I'd need a sump pump but it runs often. Of course the basement is below grade though, buts still puzzling where all the water could come from.

Not sure if that helps in your question, looks like your just gathering info?

 

[milkman636]

Yeah, I've seen old houses with split trees for beams resting on piers, so I know wood can last a long time. This is really the first time I've looked at a house with dimensional wood walls and plywood sheathing below ground instead of block or poured concrete. Like anything new its always a little scary. If its good, why aren't more people doing it? And if its bad I want to know before I go any further. Or maybe it is the best thing since sliced bread and word hasn't gotten out yet?

I am banking that there might be a few guys on here that have done it or know something about it. Seems like this group collectively knows something about everything.

 

[Sodo]

Well being 87 years old it's old growth douglas fir, which is pretty rot-resistant. If 'your' posts are some kind of softwood pine it might not fare so well.

Can get good info on TBN, but theres lots of guessing too and can be difficult to sniff out what's a guess - they tend to back up guesses pretty well. I doubt wood foundation is better in any way except more economical and faster to build which were not trivial reasons back in the day when folks weren't as wealthy as today. But it's no longer allowed in the code.

 

[MossRoad]

My wife and I have been in the market for a larger house for a while now. A nice one has come up for sale near us that has the bedroom space that we need and a nice parcel of ground, but it has a wood foundation. The basement floor would be at least 6' below grade at the front, and the grade tapers around toward the back of the house so it ends up being more of a daylight type basement somewhere around 4' below grade along the back. The basement walls are almost 100% drywalled and finished.

The house was built in 1997 and everything about the place looks like they didn't cut any corners. The materials, finish, and workmanship all look very good. The owners are the original ones that had it built. The husband died and the wife is selling it. The house sits way back about 1500' off the road in what used to be a farm field. The neighboring field is freshly tilled and is a typical loam soil. Grade is slightly sloped away from the house but then flattens out for 100's of feet around it. Its the type of setting where I would expect mud to be an issue in the spring.

The basement is dry with no visible signs of wetness and no musty smell at all. But it is also fall, not spring when its raining and the ground is thawing. I'm always concerned about groundwater, but because of unfamiliarity with wood foundations I am more concerned than normal. My wife wants to buy the place, but I need to know more about wood foundations. So does anyone out there have any insight for me on how they are constructed and what to look for?

I'm accustomed to our current home that is on the highest spot along our road, and our basement is bone dry and doesn't have a sump pump or even a crock for one. Am I being over-concerned about ground water issues?

No, you are not being over-concerned. This is probably the biggest purchase of your life, so be concerned.
My father was an architect and construction specification writer. He was fascinated with new building technologies. I remember watching a show with him about a house with a permanent wood foundation. He said they are O.K. in some applications, however, he would never use one. Too many things to go wrong. Moisture, frost, freeze, insects, ground water, rot, improper installation, etc... are all real concerns. In a nutshell, Roman concrete is still standing 2000 years later. :confused3:

If I were you I'd contact some sort of building inspector, engineer, that sort of person, with some knowledge on the subject and ask them how those things hold up in your area. Also, see if you can find any of the original plans at the local building department. See if you can find any drainage plans. Look for ground water maps. Soil maps. Topographic maps. See if you can locate the original builder. See if the owner knows why they chose a wood foundation. Maybe it was purely on price. Sounds like a nice place, but do your homework. To get it replaced, you'd have to jack up the house, remove the foundation, pour a new one and set the house back down on it. Not cheap. Good luck. I hope it works out for you. :thumbsup: Also, look for transferrable warranties from the builder/manufacturer of the wall system.

 

[TCowner]

I have the wood foundation in my house that was built in 1989. I was a little skeptical at first but would not hesitate to build/purchase another. The wood foundation manufactures are quite demanding in their installation program. The key element in their program is to move water away from the foundation. I was quite amazed at the amount of pea rock and drainage tiles that were used below and around the foundation. In 25 years we have not had any water leakage issues in the basement and during this period we had some very wet springs and some very heavy rainfalls.

If a foundation is going to take on water it would mine. The soil here is made up of about 1 foot of black dirt, then 6 feet of clay and limestone followed by solid limestone. Needless to say, its holds moisture.

The obvious question is what happens 50 years from now, or a 100 years from now. I won't be around to answer the question. But when you hear about problems that traditional block and poured concrete foundations have then this system has as good of chance of long term survival in my opinion.

 

[newbury]

Well since the OP doesn't describe either the wood or his location (

Palm of the Right Hand

MI? AK?) it's difficult to make a good comment. We need more info -

What's the wood contacting the GROUND? Old growth Doug fir? Cedar? SYP? Cypress?

What's the climate? Southern Florida? Arizona? Alaska?

In one of my "neck of the woods" (MS) almost any wood except Cypress would be subject to termite feasting. In northern Vermont spruce might be OK. But unless wood basements are a common practice in the OP's area (ask several real estate agents) I'd steer clear.

 

[mfreund]

Time for a local building inspector. We had a whole house inspection done and would not buy a house with out one. When we bought our house the $600 inspection got us a $10000 dollar roof.

 

[farmer2009]

There are a few wood basement houses around here. My grandfather build several of them back in the 50's. They are wood that is then layered with a tar like water proofer and sometimes a mesh or plastic. The key is the exterior weeping system. He always ran pipe at two different levels and has gravel fill and filter fabric around them. They didn't leak then and to my knowledge and his they still don't. If the outside weeping is done right there is no need for an interior weeper.

Find the drain outlets and have a plumber run a camera all the way through the loop. Also try to determine if the pipe is at or below the grade of the basement.

Then take a shovel and dig below grade won't take much to see what kind of water proofing was used. Also find the interior sump pump pit.

 

[dave1949]

I've only seen one constructed, around 1980, NW Ohio.

They dug out for a basement as normal, then put down pea gravel and leveled it. The basement walls were built like a standard wood framed wall using treated lumber and treated plywood sheathing. Those were set directly on the pea gravel, just like setting a wall on a sub-floor. I don't know any drainage details.

I have no idea how it worked out since we left the area in 1985.

The problem with anything non-standard in housing is, whether it is perfectly fine or not, the market has skepticism, as you do. It was cheaper and faster to build, it should be priced as such. You would be taking on the ownership of that market skepticism.