Leveling Slab

[Dickey]

Due to all the dry weather the brick on my three thousand sq. foot house had cracked in several places so I called a contractor to get an estimate on leveling the slab. Twenty one thousand five hundred dollars is the estimate. Sure seems very high to me. I’m thinking about buying a backhoe and trying to do the job myself although I’ve never done any work like that. I sure could use some experienced advice.

 

[JJT]

Need more info, how old is the house? how big are the cracks? is the foundation cracking? was the house built on fill?

Sounds to me like you have a sub-standard foundation. Getting it level might be the least of your concerns.

How about some pictures?

 

[Paddy]

I have always wondered how a slab foundation would hold up over time. With this cost to fix, could have been built on a crawl space with poured walls.

Sorry to hear your troubles

 

[Chuck52]

Paddy,

As I understand modern building techniques, a slab foundation is still supported by piers of concrete which should extend below the local frost line at least. Our house was built in the mid 50's, and has a full basement under the main house and a 25x50 foot slab under the garage and laundry room. The slab part has settled over the years and we are getting both cracks in the brick work and in the walls and ceilings, especially in the part of the main house directly connected to the part on the slab. I got three estimates from companies which drive steel supports into the ground to lift the slab, RamJack is one of the national franchises, and all three came in at about $11K. They all said it would take 11 piers to raise and support the slab, and one of the reps did a vary thourough measurement job. He came up with about a 3-4 inch settlement at the lowest point, which agreed with my own calculations. The cost is about $1K per pier around here.

There's no way you could do the pier-type correction on your slab yourself. The equipment is too specialized and expensive. If you are thinking of mud-jacking, or something similar, again that might not be a DYI project. I doubt you could get under enough of the slab to raise it with house jacks without doing more damage than good, even if there were a place to position the jacks for support. I'd look into the RamJack-type fixes. Some folks swear by them; some swear at them. I suspect it depends on the soil type in your area. It seems to be the only way to go for my problem, and I plan to get it done this year. I'm tired of adjusting doors only to have them stick again in a few weeks/months.

Chuck

 

[EddieWalker]

Foundation repair is one of those specialized industries that has more issues than just about any other. You can't unbuild your house, so getting it fixed is your only option. I get calls on this all the time and refuse to even look at them, but I've been told stories by dozens of clients of foundation repair contractors comeing in, doing a bunch of work, and fixing the problem. But then the next year, it happens all over again. What's really disturbing isn't that most repairs don't work, but that these guys are not in business more than a few years and rarely return calls when the foundation starts to move again.

I don't know the answer or which system realy works. It's probably a locallized thing. In one are, one method might work, but in other areas, a different one will fix the problem.

My advice is to talk to everyone you can in your area. Be extra cautous of all of them, big national companies too.

Good luck,
Eddie

 

[Dickey]

The price was for fifty piers on four foot centers, I think they drill them into the ground ten or so feet deep so moisture is not so much a facter in this clay soil. Thank's for the input guys.

 

[Paddy]

When you say slab on piers, is there a continious beam at the parimeter conecting those piers?

If the piers are sinking, doesn't sound like they are frequent enough. I would think a continious below grade wall back filled would be the only way to have a soild base. In my area, only small track houses are on slab. I can't imagine a 3000' sq home of decent quality on a slab. A poured bacemnt costs only $12 a sq-ft after escavation. The poured wall act like a 8-10' tall beam. very stable.

 

[toolaholic]

I'm a ca gen contr. go to chance helical anchors on the net. you're about to get an education! we've used them for years! tool

 

[CurlyDave]

I'm a ca gen contr. go to chance helical anchors on the net. you're about to get an education! we've used them for years! tool

Wow!

That looks like the right way to do the job. How much does it cost?

 

[dmccarty]

Dickey,

Did the actual brick crack or was it the morter? Is it happen around the entire house or just in one locations?

Get and engineer to look at the problem and propose a fix. A coworker had a structural problem. He paid a couple hundred dollars for the engineer and his solution. The solution was a 4x4 and some concrete. I don't think you will be this lucky though.

I have never seen a slab built on piers. The way I have seen them built in is to just dig a 24 inch wide trench at least 12 inches deep and pour concrete for a footer. Build up a wall on the footer. The pad is poured inside the wall. In my area of NC the frost line is something like 6 inches so this works just fine. 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.

I would think the solution of the piers every four feet would defeat the expansive clay but I would get an engineer to look at the problem first.

Later,
Dan

 

[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