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I recently purchased a house and it has a very nice, solid backyard patio slab. The slab has no cracks whatsoever and is attached well to the house's foundation/slab. However, due to the property being downhill towards the house, the corner of the slab (not the one attached to the house) has sunken a few inches. I would say 2-3, maybe 4 inches at the most. It currently looks ok. It doesn't look or feel sunken, but I have noticed that when I get heavy rain that corner floods a bit. Also, the soil has pushed against it over time that it has formed a bump higher than the floor level. I just built a french drain to make sure the water doesn't come towards the slab or the foundation and now I want to install tile on that patio and I was wondering if I can pour mortar or concrete on that corner to raise it and bring it to level. I will use a floor leveler once it's all leveled, but I feel like I need to fix that corner first. Any recommendations or suggestions on how to raise that corner without having to jack it up, etc? The total area to be raised is about 5 square feet. Thanks in advance!

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  • A few years ago, used to see adverts for raising cement steps/landings. They seem to drill holes and pump a slurry or benonmite(?spelling) underneath and raise it up. Do not know if it was any good, but looked neat. – crip659 May 18 at 20:09
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    Mud jacking may be a possibility depending on the soil conditions different mixtures are used. But just 1 corner? Could it have been poured that way and the soil movement is the problem? I would want to check the slope of the slab and evaluate that because you want the water to drain away from the home. The earth may have moved after a wet year. – Ed Beal May 18 at 20:43
  • Yes, the slab is sloping down from the house towards the backyard. It's only that corner that's lower than the opposite corner. The land slopes in that same direction though. Not sure if I should just ignore it and tile as it is. It won't be a flooding issue with the trench drain, just more of an aesthetic issue since the pergola support looks a bit higher at that corner than the other one. – Clemente May 18 at 21:46
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    Some pictures would help us see better and maybe give a better answer. – crip659 May 18 at 21:51
  • I've seen minor adjustments made by cutting a chisel tip and pounding PT 2x4s under the edge, like chopsticks under a rug. Maybe call it "mud poking"... Might not get it perfect, but could save money and effort on leveling aggregate by reducing the slope somewhat. Might also be able to dig out a bit and bottle jack up the corner, then fill exposed gap with brick chunks, gravel, etc. – dandavis May 18 at 22:06
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Since it's draining away from the house, I'd just correct the grade of the soil beyond it so that water isn't trapped and is free to keep flowing away; and leave it be. Dirt is easy to reshape - giant slabs of concrete, less so. If it's grass, peel back the sod, fix the level, roll the sod back down and water it well for a month.

There are ways it can be raised - "mud jacking" is the term of art, basically pumping grout under the slab to raise it hydrualically. Can be expensive, may be difficult to find a local who does it, may cost a lot to bring in a non-local to do it. So I'd pass. If the look of the pergola support is the hill you want to die on, consider that nobody but you will know if you make the pergola supports all the same height and let the top of the pergola not be level ;-). I bet nobody but you notices the difference in the posts if you do make it level...

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  • Well, thank you! I mean, I just wanted to have a somewhat leveled porch but you are right. I am not sure how much leveling by a professional costs, and I wanted to do it my self, but only if it's a simple process like pouring concrete over it. I can definitely level the soil around it and reshape that area so water doesn't get in. And with the french drain I installed, water has no change of coming close to the house or the porch, unless we get tons and tons of rain, but even then, the house is in a hill, so there's no way it can ever flood. The neighbors house is about 1.5 ft lower. – Clemente May 19 at 22:39
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I recently just watched a YouTube video on doing that to a sidewalk. They actually used many cans of spray foam, and showed later how it was holding up. Possibly search for "Spray can foam level concrete" or "sidewalk" instead of "concrete". They drilled holes just large enough for the tubes from the cans and kept spraying until it raised up. But I also recall he put too much in, because it continued to slowly raise up after some time. https://www.youtube.com/results?search_query=spray+foam+level+sidewalk This shows up some good results for me.

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  • Thanks for including both the description & the link! TBH, without a lot of practice, this method seems to be very hit-or-miss - as you noted, in the video they overfilled, which, in the OP's case would be bad because it would direct water back toward the house. Also, (not having watched the video), I presume this isn't your standard insulation spray foam, but something specific for the purpose? – FreeMan May 20 at 12:52
  • No, it is generic spray foam for insulating. And they previously paid a LOT for actual pumped in concrete, that made more mess and didn't last. I don't know if I could do it myself, but if it was that, or tear up concrete, I would give it a shot. – Pioneer4x4 May 21 at 20:17

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