Sunken concrete patio, what to do?

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Old 07-16-13, 05:03 PM
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Sunken concrete patio, what to do?

Hello,
I unfortunately have a 10X12 concrete patio that has sunk about 8-10" from my foundation. My first inclination was to have it mudjacked. The contractors didn't act like they wanted to do it, and the price was around $2K, with one guy telling me it would be less expensive to break it up and pour new concrete.

So... I decided to try to break it up myself and save money. Rented a concrete saw, which was extremely slow and found out my patio is extremely thick (4" on one end to 10" on the other). Took the concrete saw back.

So... decided to pour a concrete pad over the existing one to get it back to shedding water away from the foundation. Set up my forms and noticed how thick it would have to be next to the foundation (around 9"-10") and how much weight with the existing pad would be pushing against the foundation, and am rethinking that option.

Is trying to save money out of the question here, will I have to tear up my yard with a skid steer and $$$ to remove? Or should I go ahead and attempt to pour concrete over concrete and take my chances. Side note, I may be living here a max of 2 more years. Thank you!
Matt
 
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Old 07-16-13, 05:10 PM
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Got a picture?
8 to 10" settling is a huge amount.
Someone would of had to have laid this over a lawn with no prep work to got that much.
 
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Old 07-16-13, 06:07 PM
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The sunken 10" is next to the foundation. I think when the house was built it was thrown in as an afterthought with no consideration for the base washing away. Eventually the rebar broke and the slab fell 10" and now all my water is rushing toward my foundation
 
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Old 07-16-13, 06:19 PM
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Number 1, I never would have used rebar to attach a slab deck to a foundation. There was suppose to be just an expansion strip between the two.
A slab mores up and down a small amount a foundation should not.
 
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Old 07-16-13, 06:29 PM
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Pour a wet mix around the edges, following your forms. Fill the rest with crushed recycle. Pour sand on top & brick it.

Or

Remove the patio completely & bring in top soil to fill the gap. That might even be cheaper.
 
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Old 07-16-13, 06:51 PM
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Agreed! What the heck were they thinking? Apparently 40 yrs. ago in my area, concrete was cheap and readily available but intellect was not.
 
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Old 07-16-13, 07:31 PM
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The uniform pattern of mortar-filled holes indicate that the slab has already been mud-jacked. That job was either done incorrectly, or additional settlement has taken place since then. I'd be very leery of trying more mud-jacking, as there's a good chance of blowing in your basement foundation wall.

Break up the slab and start over if you want a concrete patio back there. This time, rent a 90-lb. breaker hammer from a construction rental supply place instead of a concrete saw. Work your way inward from the perimeter, pointing the breaker's chisel tips towards the outside to give the broken concrete a place to move to. The last time I rented a breaker, it was $25 for a day, and it only took me 6+/- hours to remove a 10' x 10' slab (spent more time loading concrete debris into the pickup than I did breaking it up).
 
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Old 07-17-13, 06:23 AM
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I agree with bridgeman about the breaker, but I think he may be underestimating the cost. An electric jackhammer may work on 4" thick concrete, but is next to useless on thicker slabs. With a pneumatic 60 or 90 lb. jackhammer (run off a large towable air compressor), you could have the slab broken into liftable chunks in about an hour and a half, tops. However, then you need to get rid of the chunks somewhere. You've also got to bring in a bunch of fill stone, place it, compact, it, then form, pour, and finish the concrete.
At the risk of being repetitive, some things are just not DIY projects. In my opinion, this is one of them. A contractor could come in with his equipment and have the entire job done in one day, from removal to finish. Compared to the headaches you will endure and the questionable results you will achieve, you'd probably be better off hiring it out. Professionally done, when you sell the house in 2 years there should be no problem. If you screw it up yourself, you may have to either lower your asking price or have it redone professionally anyway.
 
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Old 07-17-13, 08:01 AM
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Thank you all for your input! I'm leaning to renting that 90lb jackhammer/breaker and not pouring a new concrete patio. I'm going to replace the concrete patio with an addition onto my existing wood deck.

Wonder if anyone has opinion on dexpan, its a mortar type mix that you pour into holes in the concrete and it expands, breaking up the concrete. It should would be easier than jackhammering and I've already got holes drilled for the rebar. Although if it expands, wouldn't it also expand the slab into the foundation? Just trying to save my back, but I don't want to damage the foundation. Thanks again for all your help,
Matt
 
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Old 07-17-13, 04:22 PM
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So what I mistakenly thought were mud-jacking holes are actually holes you drilled? My bad. But for an expanding cement to work, I think your holes are too far apart--usually 8" or 9" is the maximum spacing.

I'm not familiar with dexpan, but I have used Sumitomo's product, called S-Mite. It works like a charm, breaking up rock and concrete by applying compressive forces along the hole pattern, putting the rock/concrete in tension as it cracks along the filled holes. The trick to not damage an adjacent foundation is to always start and work along the outside perimeter, giving the concrete a place to break towards, away from the center mass. Similar to the method for using a breaker hammer that I described earlier.
 
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