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Old 12-12-2011, 03:56 PM   #1
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Repairing a sunk concrete slab


I'm new here and would love some insight on an issue with a home I just purchased. The home was added on to probably in the mid 70s. The addition included creating a paneled room with rolled roofing over an existing exterior concrete porch. The room itself is well constructed and seems to have held up well over time.

The problem is that there is one corner of the room that has dropped down significantly. I wouldn't be surprised if there was a good 6"-8" drop from one corner to the other over a 10 foot span. The odd thing is that this patio was like this when they built the room around it. Instead of paying to repair and level the concrete they simply built around what they had and filled in the gaps with foam insulation.

I am guessing this thing is done settling as the previous owners say it has remained as is for the 30 years they had been there. I need to find a solution as it is not only aesthetically displeasing but I also trip over the drop off where the slab has cracked every time I walk through. I don't have a ton of money to spend and don't plan on living in the home more then maybe 3 years so even a temporary solution would suffice. The porch will be covered with carpet so what it looks like does not matter as long as it is close to level.

Any suggestions on how to proceed with the repair? If I can spend under $1000 to fix this it would be preferable. The entire porch is probably 20x10. The damaged section is maybe 6x10, gradually sinking down in one corner.

Any help is appreciated.


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Old 12-12-2011, 04:58 PM   #2
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Hydraulic cement pumped into cavity below to raise the pad.


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Old 12-12-2011, 05:17 PM   #3
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Mudjacking. Lot's of info with google search.
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Old 12-12-2011, 05:28 PM   #4
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As Joed noted, a common solution is mudjacking. Unfortunately mudjacking (which uses low viscosity grout, not hydraulic cement) is not a DIY project due to the high cost, specialized equipment required. I doubt anyone is going to do this job for under $1000, you can always get bids to see.

The other option is to place concrete above the slab to bring it back to level. This can be done using special types of concrete bonding agents designed to accomplish this type of task, check out the Thoro Corporation or SIKA, which make special bonding agents. That type of project may well be DIY.
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Old 12-12-2011, 09:40 PM   #5
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Was this conversion done on a proper footing and foundation? It doesn't sound like it.
Did the addition have a C of O for the conversion? This is something that should have been checked out as part of the purchase research.
A room that sinks that much can't be said to," (be) well constructed and seems to have held up well over time."
"They that can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety."
B. Franklin 1759

Last edited by Ron6519; 12-12-2011 at 09:42 PM.
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Old 12-12-2011, 11:32 PM   #6
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Thank you for all the responses. I have looked into mudjacking in the past. I have a few contractor friends that suggested this. Unfortunately it is quite expensive where I live. I don't really have a "guy" that can get me a deal on it either.

I got the house at a bargain and it was fully inspected. The room is not built on the same foundation as the house. The older couple that use to live there literally had a sunk porch, which I imagine occurred due to water washing out the soil underneath it, and built a room over it. The porch was sunk before the walls and ceiling were put up around it. They even have the molding angled level with the drop off. The rest of the room appears to be structurally sound and is not sagging or uneven anywhere I can see.

I am much more keen on the idea of leveling over top of the porch. As I understand it this is not the correct fix but should suffice for the foreseeable future. There will be carpet laid over it so I'm not worried what it looks like. Will this holdup for a good 3 - 5 years? The only pitfall I can see is the saleability when I decide to move. Does anyone have anything else to add? Any other suggestions?
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Old 12-12-2011, 11:42 PM   #7
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I think that it is altogether too obvious that the "porch" room is and always will be substandard.
I for one can not in all good conscience provide you with any "temporary fix" for something that will never be fixed correctly and then you sell the mess to someone other sucker down the road.
The best I can do say, suspend the house up on beams and cribbing, remove/repair the non-footed slab by putting real footings under the walls.

Build it the right way or tear the room out.

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Old 12-19-2011, 08:34 PM   #8
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if it was built on the slab while it was unlevel if you were to jack the slb wouldnt that make the structure unlevel then? rip it out start over.


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