Concrete Lifting? Anyone heard of it or had it done?

[zekmoe]

I saw an ad for Concrete Lifting, where they come and move or reseat a small slab of concrete rather than replace it. Happens to be that I have a concrete walkway, where 4 of the squares seem to have sunk a bit on one side, leaving a 2 inch or so lip on the next one. They're about 3ft by 3ft squares, typical of new house construction. THey're not in perfect shape, and there's been some chipping on the top, but none are cracked. I'm no do it yourself-er so replacing them myself is out of the question. Has anyone had this done, or heard of it? The ad shows exactly my scenario, where a small lifting tool digs them out or or fork lifts them up and they must put rocks, sand or whatever underneath to level. Ideally I'd have it all replaced but post divorce I'm short of that discressionary money. Opinions?

[pokey]

Never heard of lifting with a forklift. Usually they drill holes and inject "mud" under pressure to fill the voids and raise the slab. It's called mudjacking.

[zekmoe]

The pic may have not been a forklift, only the wedge pieces that made me think that. It may have been what you said, some sort of wedge that they injected the lifting stuff. Does it work and is it cost effective? Walkway is 9yrs old.

[recto-robbie]

Never heard of lifting with a forklift. Usually they drill holes and inject "mud" under pressure to fill the voids and raise the slab. It's called mudjacking.

dont know too much about this stuff but pokey here is correct, my father had this done to his driveway about 15 years ago.
They drilled a bunch of holes and injected with immense pressure more concrete which actually lift the individual slabs so they could all be evened out. Seemed to work fine.

http://www.concretenetwork.com/concrete/slab_jacking/what_is_slab_jacking.htm

[Barefoot]

Saw them do that to a patio on This Old House or Hometime or one of those shows....worked for those guys.

[Boobala]

An alternative MIGHT be to simply poor some more concrete on top of the lower slabs and then make them level with the others.

http://www.naturalhandyman.com/qa/qarepairslab.html







.

[thewhit]

After the 89 quake here in California, my house in the Santa Cruz Mountains was leaning from the major jostling. My garage had not been bolted to the foundation and chattered off center and bowed the walls.

A company came in and with a method called pressure grouting, lifted up the entire back of my house. They drove pipes deep in the ground in several spots and injected the material until it hardened. They returned the next day and raised the pipes a little at a time with the new liquid material pushing off the hardened base. As they pulled the pipes closer to the surface and kept pumping the house began creaking and it rose up to the desired level, as the ground swelled. It was pretty amazing and I know they do it to bridges too.

Should be no problem for your needs.

[zekmoe]

I'm looking at four 3ft by 3ft squares. Any hazzard to guess what it's gonna cost? I haven't called for an estimate.

[Allthumbs56]

In our area there's a franchise called Jo Jacks that does the hole-drilling, pumping thing. We had a number of slabs lifted last fall - one almost 6 inches. They lifted about 6 slabs and drilled about 20 holes to do so. It cost a total of about $700, and that also included some grinding of a few high sides. No exactly cheap - but a lot less than digging up and repouring.

[djem]

Never heard of lifting with a forklift. Usually they drill holes and inject "mud" under pressure to fill the voids and raise the slab. It's called mudjacking.

Correct, but I think the mud is actually a cementitious grout that cures/hardens under the slab.

Our City Works Dept. levelled uneven sidewalk 'tiles' using this method. And yes, it does work and has lasted without any shifting for well over 15 years.

PS - we live in a typical 4 seasons climate with some pretty cold winters so this method seems resistant to freeze-thaw cycles.

[djem]

In our area there's a franchise called Jo Jacks that does the hole-drilling, pumping thing. We had a number of slabs lifted last fall - one almost 6 inches. They lifted about 6 slabs and drilled about 20 holes to do so. It cost a total of about $700, and that also included some grinding of a few high sides. No exactly cheap - but a lot less than digging up and repouring.

If someone proposes to lift the slab and replace with new, the most important thing that has to be done is to redo the sub-base with a properly compacted engineered fill. Without proper compaction, you are pissing away your money. In my line of work, I always keep an eye on the contractors to make sure they place and compact the fill prior to placing concrete.

[sws1]

WOW - Cool. I need this. I have LOTS of concrete slabs on my property. Several of which have started to lean towards the house. I was dreading having to redo all this.

[Bryan316]

I had a company quote two houses, mine and my parents, to level both our driveways. Mine, because of how severely it sank (9 inch drop next to the house, horrible rain flooding problem) and how poor the 60+ year old concrete was, came in at $950. My parents' driveway, being fairly new but being lots of driveway to fix, was $750.

To replace my parents' driveway's problem areas, they were quoted over $4000.


You do the math.

[aeolian]

I've also heard of polyurethane foam used to inject under slabs and raise them up. I was looking at houses in an area with soft soil and several needed help. So I was researching this. I ended up finding a place in a different neighborhood as the only sure way I found was to tear out the old foundation, compact the soil correctly, and put in a new one.

For a walkway, it's much less critical and squirting something underneath would probably be fine.

[Bryan316]

DON'T DO THE FOAM.

Contact a company who injects concrete. They use hydraulics to force the concrete mix under the slab.

The foam will get chewed away by rodents and earth dwellers and used to make nests.

[pokey]

Correct, but I think the mud is actually a cementitious grout that cures/hardens under the slab.




You mean like concrete?





mud is a generic term for concrete and whilst the " mud" they use has a greater amount of fly ash it is for all intents and purposes concrete.

:D

[BluesForDan]

my A/C heat exchange unit (that sits outside the house) is on a concrete slab that is sloping. I didn't know they could inject something under them to level it. Who does this kind of stuff?

[djem]

You mean like concrete?





mud is a generic term for concrete and whilst the " mud" they use has a greater amount of fly ash it is for all intents and purposes concrete.

:D

Add a coarse aggregate (IE: stone) to the 'mud' and you'll get concrete. ;)

The only time I've heard concrete and mud used together is in the term 'mud slab' which is what we place when subgrade conditions are not favorable to compaction and levelling.

I've also used a mud IE: drilling mud (bentonite) when performing underground (U/G) drilling operations for large scale U/G pipe installation.

[telejammer]

If the slabs are only 3'x3' why don't you just use a 6Ft. long digging bar and wedge it under the low side and lift the slab high enough to work under it. Throw a brick or piece of wood under it to hold it up while placing "Fast Set" concrete under the slab to desired level. lower the slab back down and check with a level, when the slab is level your done. The moisture from the ground will harden the concrete under the slab. Total cost, about $35.00 and and should not take more than a couple hours to do even if your a novice. One 80# bag per slab should be sufficient.

[djem]

If the slabs are only 3'x3' why don't you just use a 6Ft. long digging bar and wedge it under the low side and lift the slab high enough to work under it. Throw a brick or piece of wood under it to hold it up while placing "Fast Set" concrete under the slab to desired level. lower the slab back down and check with a level, when the slab is level your done. The moisture from the ground will harden the concrete under the slab. Total cost, about $35.00 and and should not take more than a couple hours to do even if your a novice. One 80# bag per slab should be sufficient.

Good tip but I would like to correct something.

Concrete cures on it's own due to a chemical reaction. In theory, concrete cures forever getting stronger and stronger as time passes. Water, whether it be applied to concrete or present in the surrounding material serves only to control this reaction, actually slowing it down to avoid tension cracks due to the surface curing quicker than the concrete further away from the exposed surface.

Typically, you water cure concrete when it's hot and in direct sunlight by throwing burlap on top and spraying down with water (just one of the many methods).

[telejammer]

You are correct about a chemical reaction in the concrete making it harden, which is adding water to start the reaction, or moisture in the air or humidity will start the harding process. Portland cement, which is used to make concrete is mixed together with sand, gravel or stone or some other type of aggregate . Water is then added to start the the chemical reaction and everything is mixed together. Slump is a term for measuring the amount of water or moisture content in the pre-hardened concrete mixture, ideally a 3-4 inch Slump is good for residential slabs that are typically 4-6" in thickness. To make one more thing clear, the chemical reaction that causes cement to harden can not take place if no water or moisture is present.The Fast Set concrete I was referring to is the same as post hole mix, thus no mixing with water is needed, just place under the raised slab, float it out and lower the slab back down making sure slab is level. If you want it can be misted with some water before lowering the slab, this will speed the hardening process. The advice I was trying to give was a simple, cost effective alternative that the average person could perform. The other way is hire a professional contractor.