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houser 12-14-2006 08:58 AM

slumped patio fix ??
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Hello all,
I am looking for comments on how to handle a slumped concrete patio on a house purchased this past summer.

15' x 8' patio set longways against an 8' ell corner of the house. The patio is concrete, and made out of two separate pours. The first pour sits on an unknown base, below grade, and is at least 10 in. thick. The second sits on top of the first pour, and is about 9 in. thick. So, I have at least 19" of concrete on this patio which, at about 200 cubic ft, and at an average of 150 lbs/ft3, comes in at about 15 tons. The patio has no roof, but I have 3.5' overhangs on the house, so that much of the patio is covered, but enough is open that when it rains, a significant amount of water loads the patio.

The problem:
The patio has one large crack running crosswise at the middle of the pour (perpendicular to the house and the 15' length). The concrete is slumped in towards this crack. Additionally, the slab is slumped back toward the house, so that the slope of the slab is both toward the middle, and toward the house. So, any rain is funneled down the vee crack in the middle, and runs down between the slab and the foundation, enlarging and furthering the slump toward the house. Separation and downdrop against the house is obvious. Also, the siding (white vinyl) sits directly on top of the pour, but has pulled away somewhat by the slumping. (BTW, whoever invented white vinyl
siding should spend eternity fixing the same buckled piece, in sub-zero weather :)

My goal:
fix/replace concrete so I can mortar on a nice stone surface at proper grade away from house.

1) If I just top with a leveler and regrade, I would have to remove siding and re-starter it. And though I plan on re-siding the whole house anyway, just leveling the top leaves the problem in place. Like a cavity, the slump will not magically disappear. So I'm not fond of this one. Don't really like the idea of concrete topping anyway.

2) Slab-jack with portland slurry. This one would fix the cavity slump, but is it possible to jack a slab that comes in at 30,000 lbs? I would also have to re-starter the siding for this fix, since the grade would not be lowered, but slightly increased. Any slab-jackers out there?

3) Jack-hammer away top 6 inches or so, stabilize cavity with slurry, re-pour, then top-stone. This is a good fix, maybe the best, but also the most work!

Sorry for the long post, and best to all!

concretemasonry 12-14-2006 12:37 PM

Some thoughts:

1. Topping will just crack again since the old crack will telegraph through. The poor backfill placed by the contractor during construction is still unstable.

2. Slab-jacking or mud-jacking is a proven method to raise and level concrete. I have seen complete concrete stair and landings raised and leveled. Contact a local contractor and have him take a look at it.

3. A possiblity.You will get a better looking job if you replace the 9" concrete patch someone applied. Mud-jacking would be the best way to stabilize the remaining concrete and holes required for jacking would be covered by the new topping.

houser 12-14-2006 12:46 PM

Thanks concretemasonry.
Any reason to replace the whole 9", as opposed to chewing down only 5" or 6"? Lots of extra work, and it will all be hidden anyway, since I plan to stone the side walls as well. Also, is there a diff. between mud- and slab-jacking (with portland slurry)?

thanks again for your thoughts!

concretemasonry 12-14-2006 02:22 PM

slumped patio fix ??
No special reason to take off the whole 9", but it just break off at the bond anyway depending on the preparation.

Take off what you need to to get a convenient, usable elevation after topping or veneering.

A mudjacker can set the elevation or slope. Make sure it drains. Normally mudjacking has a very long life, but you never know what is down there.


cornbread 03-18-2010 05:42 AM

It's not always a bad job by the contractor. We did a stamped concrete patio and I'm trying to determine if it can be fixed without drilling holes through the concrete. Mine will eventually crack but it has not yet. I have 8 ft of backfill under my slab. I should have known that it was going to sink some. The only true way to prevent sinking slab over backfill is to backfill with rocks which is $$$$$$ or build piers and use rebar.

stadry 03-18-2010 06:25 AM

i'm w/dick :whistling2: but if it were our house, we'd replace the whole thing including fail'd base,,, you do want to consider freeze/thaw in your area,,, successful stone top depends on NO wtr entering the grout,,, i never recommend stonework on top of conc - even down here in atl,,, it all depends on one's definition of ' time ', tho

corn's job's different,,, IF the base were plac'd in compact'd lifts of proper base mtl, probably wouldn't have settl'd,,, doubtful he did that part, tho.

( bring back the muskie )

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