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ason83jay 09-22-2010 11:48 AM

Sinking enclosed patio
I have a house that was build really well in the 50's, but everything done after that, including an added enclosed patio was done poorly. The patio is about 10 feet deep and 20 feet wide. I just finished replacing the windows and siding for the house and patio. Now I pulled up the floor in the patio and found that the floor is cracked from sinking. One small section is still in good shape because it was poured over the old concrete stoop leading from the back door. The rest has sank about 4 or 5 inches.

I had an animal digging under the patio a few years ago and have since then covered up the hole and not had any more animal problems. But I believe there is no footing or at least not a good one. I also think a portion of the patio is just floating now.

I thought about pouring a concrete mixture over the top to level everything off, but I know it will continue to sink and crack. A contractor suggesting cutting out the floor as close to the walls as possible and pouring a new floor. I'm still worried that the old concrete will continue to sink and crack the new concrete or separate from the new concrete.

Is there anything that can be done shy of tearing down and pouring a new foundation? If I jack up the structure to pour a new foundation, I am affraid the new windows (which are now level) will crack. Can I add pilings to support the walls? Or can I use rebar to structurely connect the old to new concrete? Any help is appreciated.

rory_88 09-23-2010 06:16 PM

You definitely do not want to pour on top of a sinking slab. That will just add weight making the problem worse.

You can't remove the floor w/o taking down the structure? What about cutting around the perimeter or is the structure on the move as well?

ason83jay 09-23-2010 06:21 PM

I think it is very possible to cut around the perimeter and pour a new floor. But I'm concerned that the remaining concrete around the perimeter (which has all of the load on it) will continue sinking and either separate from the new concrete or at least crack at the joint between new and old. I am a mechanical engineer, so this is what makes sense in my head, but I do not have any experience with concrete at all. I only know what I can find online.

Should I not worry about the perimeter of old concrete sagging after the new floor is poured? Or is there a good way to support the perimeter of old concrete so it doesn't continue to sag?

rory_88 09-23-2010 07:45 PM

So the foundation holding up the structure is also shifting? If yes, you have bigger problems than just a sinking floor. You likely want to consult a structural engineer to determine if the structure be saved. There are ways to reinforce an existing foundation but it may not make good economic sense if all we are talking about is a stand alone porch.

ason83jay 10-12-2010 01:09 PM

The slab was poured up to the house foundation and the covered porch is integrated into the house structure. So I do not want to tear down the existing porch structure except as a last resort.

Someone suggested mud jacking the floor to level it off, then I would have to use a self leveling compound to smooth out the floor over the cracks. Does anyone know if mud jacking will work for my situation? The slab is cracked into 3 different pieces. The low sections are where the walls sit on the slab. Will mud jacking raise the concrete with the weight of the walls sitting on them? Or will the center of the room raise up only?

itsreallyconc 10-13-2010 02:22 PM

was about suggest mudjacking til the foundation got mentioned,,, if you need to raise/stabilize the footer, that's an entirely different item altho your contractor may have the expertise to do both - floor & footer,,, i like the screw anchor system w/foundation clips but there are others which will also work well.

1st, get the footer right THEN worry about the floor

ason83jay 10-13-2010 02:51 PM

3 Attachment(s)
itsreallyconc, I do not think there is a footer at all. I think it is just a slab poured on the ground. The frame is sitting on the slab. The cracks in the slab run from the center of the slab out to the perimeter. If mudjacking would work to raise the slab which is in 3 pieces and make it relatively level, I was planning to support the slab with concrete piers dug down below the frost line and set along the perimeter every so many feet (still need to figure that distance out). But if mudjacking is only going to lift the concrete from the center because there is more weight on the perimeter, then it won't be helpful. That is where my question came from.

Also, can you please explain the screw anchor system w/ foundation clips? I am not familiar with that.

Finally, I added some pictures that will hopefully help.

itsreallyconc 10-13-2010 03:05 PM

see what you mean - the part over the steps are fine but the rest's a mess,,, ( slab - mudjacking ) would work but, as in anything else, final results depend upon the skill of the operator,,, our pier plan sounds decent however, for me in upstate ny, i'd also place a steel reinforced grade beam on top of the columns just to make sure i didn't have to do this work again.

an excavation is dug alongside the footer & a BIG auger is then hydraulically driven into the earth til refusal,,, steel clips are then bolted onto the anchor's shank & support the foundation.

pics were a GREAT help,,, wouldn't hurt to ck w/your bldg dept 1st,,, good luck !

ason83jay 10-13-2010 03:19 PM

Thanks for the help and quick reply. I will check with the local mud jackers to see what they will be capable of.

itsreallyconc 10-13-2010 05:50 PM

call rahm emmanuel :hide: according to obama-yo-mama, he can do anything :beer:

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