Foundation advice

Drawing

Red is a concrete foundation. Black is rotting wood foundation that needs to be replaced.

Foundation issues suck. House has foundation issues. Most of the foundation will need to be replaced. Part of the house currently has a wood foundation which is rotting. There is an addition which has a concrete foundation. (See image above).

I know that the wood foundation can be replaced with a pier and post foundation. They can stabilize the house, dig and pour piers, then use metal posts to brace the house at the right height.

Is a pier and post foundation the only option? Is there a way to do a concrete foundation?

Edit: The image is a top down look at the perimeter of the house. The red part is a ~600 sqft addition. The black part is the main house.

archomrade,

Preface: I am an architect based out of the midwest, so I don’t have much direct experience with crawlspace rennovations or construction specifically, but I have worked with lots of wood construction and delt with water infiltration regularly.

Absent more detailed information (i see your other comment describing the wood piers and wood rot, but there’s still some ambiguity), I think it’s worth pointing out that concrete foundations are not the only way to prevent future wood rot.

Typically you see rot in conditions where:

  • There has been flooding under the house
  • there is moisture seeping up through the ground underneath the crawlspace
  • there is humidity in the air that is saturating the wood

The reason you’re seeing wood rot under your house is not because you have wood foundations, it’s because moister is not being properly controlled. Having not had experience on this particular situation before, I couldn’t tell you how you could approach replacing a wood foundation with a concrete one without demolishing the existing structure. It’s possible it could be done, but it’s almost certainly more expensive and won’t solve the water infiltration issue anyway.

I would reccomend determining the source of the water first.

  • If there’s flooding, install a drainage system (or repair/upgrade the existing one)
  • If there’s water seeping in from the ground, replace/install a vapor barrier
  • If it’s a humid environment and it’s not being controlled, mitigate the humidity by insulating, sealing, and ventilating/dehumidifying the space

You should not have problems with wood piers/posts if properly done. If you’re still determined not to use wood piers, I would ask your contractor about using CMU instead of the wood posts. keep in mind, though, that this won’t solve the issue of water presence and you would still likely have problems in the future if you don’t mitigate it.

TrickDacy,

TIL there is a such thing as a “wood foundation”…

Thavron,
@Thavron@lemmy.ca avatar

I’m amazed at the concrete on top of it as well. Normally (in my house) it would be the other way around.

TrickDacy,

Exactly! The other way around would’ve only been done by someone who doesn’t understand the concept of rot, afaik

Bitswap, (edited )

The red is fully concrete. That part of the house was an addition.

The black part is entirely a wood foundation. It’s the stupidest thing.

Edit: just realized what you were commenting. The image is a top down of the house perimeter.

Bitswap,

Yes! Apparently you can still get them installed in the US They still can meet code! Crazy!

victorz,

Pretty nice, since concrete is not too good for the environment as far as I’ve heard.

Building with wood and stone has been good to us for millennia. 👌

Bitswap,

Well…except to meet code for wood foundation you must use treated wood (usually treated with some kind of copper arsenic) which is not great for the environment (both the production and usage).

victorz,

Oh really. Well sh—

Thrashy,
@Thrashy@lemmy.world avatar

Chomated copper arsenate treated wood has been functionally banned in the US since 2003, and replaced with Alkaline copper quaternary or copper azole preservatives, which are generally safe, though I wouldn’t go eating off a plate made from them or anything. The bigger issure with wood foundations is that even when treated they’re necessarily going to have a limited lifespan – wood still degrades from groundwater contact over time without insect or fungal attack, and water will wash the preservative agent out of the wood over time, eventually letting fungus and termites in.

intensely_human,

Well, so has building with concrete.

victorz,

Let’s define “good”, I guess 😛

intensely_human,

Benefitting humans, as a definition.

Concrete lets people build things by moving semiliquid around that hardens.

Reinforced concrete can span big gaps enabling skyscrapers basically, parking garages, structures like that.

aelwero,

You need way more details here…

Basement or crawlspace? Do you have piers already? What’s under the wood, and is the wood above or below grade?

Bitswap,

I’m sure I need to add way more info…just not sure what’s relevant.

Crawlspace. There are piers…but they appear to be wood. Wood piers in the ground, connect to wood posts/beams above ground. As expected the wood has started to rot and the whole wood foundation needs to be replaced.

This is in the PNW and earthquakes are possible, thus my preference for a concrete foundation(rather not get into the debate about how house would be effected from earthquake).

This is not a foundation repair situation…this is a foundation replacement situation.

What else can I tell you?

pdavis,
@pdavis@lemmy.world avatar

Is the house occupied? If not, can the existing floor/decking be removed to get direct access to the crawl space and supports? If so, that will make the job so much easier.

While you are at it, have you considered digging out underneath the house and creating a concrete and cinder-block basement? It would cost a bit more but since you are already doing major foundation work, it might be worth it and would dramatically increase the square footage of the house. Adding a basement would allow you the freedom to bring in large excavation machines to do the digging with.

Bitswap,

The house is not occupied and there is access to the crawlspace.

My main concern is that I’m not sure a concrete foundation can be built underneath the house. Since it has the addition which a concrete foundation, the house cannot be lifted. The weight bearing concrete would have to be built upto the level of the house…which I’m not sure is possible.

A basement would be amazing.

pdavis,
@pdavis@lemmy.world avatar

I have seen time-laps videos on Youtube of a company that retrofits houses that have crawl spaces with full basements. It is pretty amazing to watch them work. They hand dig out sections at a time and pour footings and supporting walls, they then do a final pouring of the floor. They do this without lifting the house.

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