Foundation piers

[Chuck52]

The main part of my 50+ year old house is on a full basement, and the garage and laundry room are on an attached slab. The slab has settled a bit over the years relative to the rest of the house, and I decided to get estimates on stabilizing and perhaps lifting the slab back up to square with the rest of the house. I'm going to get at least three or four estimates, but after getting the first I figured I'd ask the collective intelligence we call TBN for comments.

Perma Jack and Ram Jack seem to be two national brands...perhaps franchises. The local Perma Jack fella came by yesterday. He said it would take eight driven piers spaced at eight feet to do the job. He suggested a minimal lift, as our settling hasn't caused major mis-alignment and, as he put it, what took many years to get to shouldn't be pushed back in twenty minutes. He said they could easily lift the slab all the way back, at no extra cost, but he would recommend just stabilizing and then doing the necessary cosmetic fixes to door and wondow frames, since too much lift could easily do much more damage than we have. Sounded reasonable to me. Then we got to the fee. About $1200 per pier, with some extra charge if they had to do the needed removal of a concrete walkway.

I have two other estimates coming, but does anyone have experience with such work? I've seen it done on a much larger scale on an elevator add-on to a local building. In that case, the elevator shaft was enclosed in an add-on structure to a building, and after a few years it began to lean. Piers were sunk and it was jacked back into alignment, but in just two years it began to lean again. This was a really heavy load, composed of a three story, limestone veneer structure. I suspect that my slab can be brought back to near alignment and then be stable, I hope.

So, anyone had this kind of work done? How did it come out, and how much did it cost?

Chuck

 

[Marlowe]

I recently repaired a foundation problem of my own. In my research on the subject I, of course, ran across ram jack. I also found out about hydraulic pumping for a slab. It sounded pretty simple to me, but what they do is to drill a hole in the existing slab and pump in concrete under high pressure to raise the slab back to where it should be. It might be a good bit less expensive to go this route and seems to me the right way to repair a slab.

By the way, I jacked mine all the way back to where it should have been all at one time. No harm done.

 

[EddieWalker]

How much did your slab settle? Is it still moving?

Sometimes in new construction, a foundation will settle over the first few to dozen years. I've seen homes built on landfill where the pipes were flexible. Not sure how they did that with the sewer ones. This was in California along the SF Bay on land that used to be marsh. The homes were selling from $500,000 to $750,000.

The reason I tell you this, is your slab may have done all the settling it's gonna do. If so, I'd pour concrete on top of the existing slab to level it out. If the walls are too short after thay, then I'd raise the walls.

I've heard allot of stories of foundation experts coming in, leveling off a foundation and stablizing the place, only to have it continue to move. It might be in a year, other times it might take ten years. Sometimes it's even worse than before.

Disturbing the soil to stabalize can actually make things worse.

Best case scenerio. They come in,do what they say they will and it's all good.

Worse case scenerio. They come in, do what they say they will and it doesn't work. Then you can't get in touch with them because they are no longer in business and you're out all you money and things are worse than before.

This happens with big name, nationwide companies. Not just small operators. They give you a great gurantee, but nobody will return your call when you call them ten years from now.

I'm very,very cautious about a home that needs foundation repair, and even more skeptical about anybody who does those repairs.

Good luck,
Eddie

 

[inveresk]

Chuck, I'd be cautious of putting in piers unless you know what they're bearing on. At the moment, I'm assuming you have a loadbearing slab off of which the walls spring. In short, the house applies a uniformly distributed load (udl) which is spread over the whole slab. If you dig down and put in piers, you're changing the load distribution pattern so that instead of a udl you have a series of point loads each of which must necessarily be exterting a greater force on the subsoil they're bearing on than the udl. Unless the piers bear onto really solid strata, then the additional concentration of forces below the piers could well cause some settlement in the future (it follows that if a fairly low udl has caused settlement in the subsoil, high point loads will do so even more).

With any building settlement, it's best to try to determine if the situation is now stable. I'd fix a couple of tell tales across cracks or known points of movement and monitor them over a period of six months or so. There are various types available, wax or plaster ones will tell you only if the movement is still taking place whereas glass ones have a gauge on them than allows you to measure the amount of movement. If your building appears as if it has stabilised, then you can undertake some cosmetic work to make the place sweet to the eye again.

Although I haven't heard of the process before, what Marlowe has described seems to me to be a very sound idea. If some sort of low viscosity concrete can be pumped below the existing slab at pressure to raise it, then it should flow to fill any and all voids and so ensure that once the pumping is done and the slab is re-levelled, you have a udl under you're slab again and not any point loads that might make your problem worse. But there's no point in undertaking any of this until you're absolutely sure the settlement has stopped.

 

[Chuck52]

Thanks, all.

From what I have heard so far, mud jacking is used more for "floating" slabs than for slabs with footings, such as I have. My slab has tilted from where it attaches to the main house and basement by probably no more than two to three inches, at the far end from the house. That sounds like a lot, but the slab is 22 feet long, and the largest crack, around a door right at the main house-slab junction, is less than 0.5 inches at the top of the door. The slab is original with the 50+ year old house, and the settling probably started soon after the house was built. I suspect that drains to move rain water away from the slab and foundation were added later, and now do a good job, but the slab end of the house, while not a really low, wet spot, is fairly flat and doesn't drain quickly after heavy rains.

The one estimator I have talked with so far made a point of saying they did not guarantee "driving to bedrock". His explanation was that they use the weight of the house as a counter-weight as they drive the pipe into the ground, and continue until they begin to get lift. I assume they then wait for some period to see if any further driving is possible. There are also some designs which use helical screws which are screwed into the ground I suppose, and that design might give more support. Perhaps one of the other companies will use those.

I think mud jacking, by it's nature, would be less easy to control, as to what part of the slab woiuld be raised. The piers, properly located and spaced, would probably give better control of the direction and angle of lift. The only description of the process I have so far doesn't mention back-filling under the foundation as it is lifted, and that would seem to me to be a good idea. Some combination of a controlled lift using the piers, followed by an injection of "mud" to fill any voids, sounds like a better idea than either piers or mud jacking alone. I'll be asking about that when I get further estimates.

I'm not sure if the settling is finished or not. It actually seems as if it moves both ways according to the rainfall we get in a season. It seems likely that the estimates I will get are going to be too high for me to get the work done this year, so I will set up some tell-tales to see if I can determine if it has reached some kind of maximum settling. If it really does go both ways, or is still settling, I can then make a better decision about whether to try stabilizing it.

Thanks again for the input.

Chuck

 

[stevenf]

Chuck, I thought only Texas had the RamJack and foundation leveling type companies. If they truly were confident in their work they would have a much more professional front end like say some engineers that could and would know how to positively fix foundation problems. They run a good scam and seem like legit but believe me dad had 40 or 50 rent houses and they were all cheap subpar foundation type houses. The best thing we ever came up with was the screw type foundation jacks, they are expensive and you have to stay on top of your never ending leveling if you wanted to not have to do sheetrock work. The first house I bought was very much like one of his one month you could open all the doors and windows the next you couldn't. I solved the problem pretty well with the screw jacks (it was pier and beam not a concrete slab) and whenever the house got out of wack I'd crawl under with someone up top and proceed to level the areas that needed it. Beware of the foundation levelers especially if your in an area subject to lots of shifting up and down, they can't fix your problem and can certainly make it worse. If you decide to go their route get references and talk to lots of people, it would be best if you can find your own people to talk to because the references wouldn't be on their list if they were dissatisfied and more then likely they'll be paid by the company references or friends and relatives. For the amount of money your talking about spending you might even consider putting an ad in the classifieds for your area asking to talk to anyone who is happy or unhappy with company X's work. I'll bet if you do you won't be using any of them because the stories run rampant around here of the stuff those type companies pull.
Steve

 

[dmccarty]

Chuck,

</font><font color="blue" class="small">( I'm not sure if the settling is finished or not. It actually seems as if it moves both ways according to the rainfall we get in a season. )</font>

When I first saw your thread I was wondering if the movement continues. From what you said I'm guessing you have expansive soil. The soil moves depending on the amount of moisture in the soil. You might want to call up your county's building inspector's or extension office and see if you are in an area with expansive soil.

I'm not sure what you can do about expansive soils with an old house but a soil scientist or engineer should be able to give you far better advice for alot less money than a company trying to sell you a service/product.

A coworker bought a house a few years ago that had some cracking/settling in the foundation. Prior to buying he hired an engineer to look at the problem for less than $200. The engineer told him to shore up part of the house, it was on a crawlspace, with some concrete footers, PT 4x4s, and some 2xs. Problem solved. The materials cost less than paying the engineer...

Later,
Dan

 

[Chuck52]

Steve and Dan,

Thanks for the input. I guess my first step should be to determine if I have a continuing movement, and about how much. I'll do the tell-tale thing for at least several months and see what I find. It's not like the ceiling is falling or anything.

I think most of Missouri qualifies as having "expansive" soil. I'm in a rare-for-this part of Missouri in that I have fairly deep top soil similar to the good farming dirt farther north. On most of my property, the black dirt goes down at least three feet before you find a gray clay layer. The black dirt is, however, somewhat clay-like itself, and I am sure it expands and contracts with varying moisture content. So.....I'll see what the other companies have to say, but I probably won't have anything done for months at least. In the meantime I've thought of a great invention! How abgout a pre-hung door in a frame that includes leveling and squaring adjustments. I envision the trim work around this door only being attached to the afdjustable door frame and just floating over the adjacent structure. Think there'd be a market? /forums/images/graemlins/confused.gif

Chuck