Hello everyone,
I was considering FPSF or sealed and conditioned crawl space. I am not sure what is feasible with this water table.
Any input or opinions are welcome, and I thank you.
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Replies
Have you looked at Diamond Pier? I don't know if it would work for you, but it just might.
High water table in some parts of the country is worse than others, so I will speak on my experience. My brother purchased a home in HWT country with a vented crawl space. It was nasty and constantly humid. We opted to seal it off and have conditioned space. That worked great for a few years, but had a season of a ton of rain fall and crawlspace got flooded with water. Our sealing worked well at first, felt like a water bed for awhile, but eventually the seal gave way and we had 2” of standing water. Water will find its way, no way to stop it in extreme conditions. The best foundation is a pier foundation with/out crawlspace. Louisiana has mastered the building in flood country, so I would give some of their construction details a look. A lot of them build raised homes with garages underneath to make efficient use of space below the home. Maybe ask around to see if anyone in the area has had standing water issues. If they have, there’s a good chance you will.
Thanks for the suggestions on piers.
That's my last resort as local contractors do not do much of that.
It could be a situation where I need to build up the foundation first, compact it and get a compaction test, then proceed with sealed CS or FPSF.
This would be a good spot for a FPSF, assuming decent bearing soils. FHB has a couple of good articles on them. https://www.finehomebuilding.com/2010/11/11/frost-protected-shallow-foundations-2
You might also look into helical piles.
Andy, thanks for the comment.
I assume helical piles are used when the bearing soils are inadequate to support the standard design of a foundation, in this case a FPSF?
Well, yes, but I don't know that your soils won't support a FPSF or any other kind of foundation. Just because they're wet doesn't necessarily imply that they aren't competent. If they're a good sand and gravel mix, a high water table shouldn't affect their bearing capacity. I mentioned the piers because I think they're often a good option that people don't think about. Here's an article on them I edited when I worked for the magazine. https://www.finehomebuilding.com/2016/05/16/time-consider-helical-pile-footings
Thanks, Andy. My site may indeed accept a standard FPSF, I will have it evaluated.
The pilings do look like a nice solution for a deck/boardwalk running through moist areas to the lake. Ever use them for fully submerged dock supports in cold climates?
One thing that's a nice feature about Diamond Pier is its ease of installation (they're rods that go in at angles, four of them per pier, rather than helical piles). I'd really recommend you check their site out. Stormwater management is getting to be a bigger and bigger issue over here in the Pacific NW, and disturbed area is part of the equation. The cool thing about the Diamond Pier system (and I'd assume helical piles) is that it doesn't require excavation of the top layer of soil. This allows what nature has figured out in terms of water table to be left alone.
PB, diamond piers look interesting. A friend of mine who sells building products just recommended them for my low areas. checking them out.
I haven't used them for that myself, but the helical pile contractors I know have all done it. They're a cool solution to a lot of problems.
Down here in South Florida almost all building sites have high water levels. The predominant foundation/floor is a monolithic slab. They used to be built pretty much right on the ground but now because of FEMA flood zones we have to install compacted fill for the slab. I've put as much as 48" of fill on a lot before so it isn't cheap and we have more floors cracking than ever due to poor compaction. Next up is a traditional footer with block knee walls to get the floor above the 100 year flood zone. Most of the time the knee wall area is filled with dirt, compacted and a slab poured on top. This technique is cheaper than putting fill over the whole house pad.