Leveling Slab

[Paddy]

dmaccarty,

When you say; "Because the frost line is so low basements are very expensive and very few people have them here. Most qoutes I got for a basement where around $40-50,000." What does the frost line have to do with a bacement? It would appear a slab is literally right up there in that frost area and effected more than the footings 8' below on a bacement.

Not trying to be confrentational just trying to understand your areas building issues.

 

[dmccarty]

Paddy,

The slabs are generally built up off a grade a bit since gravel is put on grade and then the concrete is poured on top. My guess is that given that most slabs are NOT insulated the heat from the house might be enough to keep the ground from freezing. And I can't really imagine our ground freezing 6 inches to be honest. We don't get that cold for very long. I know there are techniques to build houses with shallow foundations in very cold climates using insulation that runs horizontally AWAY from the house. I think the house and the insulation keeps the air temp from freezing the ground and causing problems.

I used to live in KY and watched 100's of home being built and everyone had a basement. I forget the exact depth but up that way the frost line was deep, something like 4 feet. Since you had to dig so deep anyway to put in a footer below the frost line, going a few more feet to dig a full basement was the correct thing to do. The basements I saw dug out where done with a large front end loader. Here foundations are built with backhoes. I could have dug out the footers for our house with my JD tractor and BH if I had wanted to get in the builders way.

I don't think he has a problem with his slab. My guess is he has a problem with his foundation and/or expansive clay.

Later,
Dan

 

[Chuck52]

The local code here in Mid-Missery is for 30" footers under a slab. I'm not sure of the code for the width, but they usually are one foot, for convenience if not for code. They are often dug to more then 30", but that's the code requirement. I really can't imagine the ground freezing that deep, but maybe historically it did. I also don't know what kind of footings are under my slab that is settling. The house was built in 1956 or 1958, and was done pretty well. I doubt there was a code to satisfy back then, but I'm hoping there are footers under there for the piers to grab onto. The guy the house was built for was known for getting his money's worth, and the basement has certainly held up over the years, so I'm hoping for the best. Piering seems to be about the only way to go with this kind of problem. I asked the estimators if they also backfill under the raised slab, but they seemed to think any voids created by the raising process would fill naturally. Seems to me it would be a good idea to pump in concrete so the slab would be uniformly supported.

Chuck

 

[dmccarty]

Chuck,

I would be concerned with just lifting the slab. How is it supported arfter it is lifted? Just a bunch of piers would be worrisome to me. Especially for a garage with cars.

Later,
Dan

 

[Chuck52]

Yep. Me too. I wouldn't think that, after what I consider a fairly high price to do the piers, it SHOULD cost all that much more to pump some concrete up under the lifted slab, but I bet that would actually double the cost.

I don't want to hijack this thread, so I'd also say that would apply to Paddy's situation, too. I'd not like to have my whole house supported just around the edges when it was built to have a distributed load under the whole slab. I don't recall if I brought this up with all three of the guys who gave me estimates, or maybe only one. I do recall that whoever I asked didn't seem to think it was necessary or valuable. Now, in my case we're talking at most a three inch lift at one corner of a 25x50 foot slab, and assuming no major voids from other sources, 4-5 yards of concrete would be more than enough to fill that sloping diamond-shaped void. Usually, the same companies who do piers also do mud jacking, so it would be another step by the same people, but EVERYTHING always costs more than I expect. One complication: In my case there is a single sewer line and both hot and cold water under the slab. Don't know what pumping in concrete might do to that. Perhaps a non-hardening mud slurry would be better?

Chuck

 

[dmccarty]

Chuck,

Besides the obvious problem of breaking the lines under the slab if concrete/mud is pumped into the void you might have to worry about those supply lines if they are copper. Seems like there is a copper schedule for being buried in concrete. I don't know if there is a schedule for the waste pipe.

Later,
Dan