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I have an old building that I am converting into a living space. The slab foundation is very old and uneven in a lot of spots. I need to level it, but I can't increase the height of the floors too much, or I won't have enough head room for the building code.

Here is a picture of the space, its hard to see the floor but it has a lot of dips and cracks in it. enter image description here

I would like the entire floor to be level, so I can finish it with tile, carpet, or laminate. My original thought was to lay sheets of plywood down and level them with shims. I would only lose about an inch of height. The obvious way would be to use leveling cement, but that is too expensive. At 800sqf it would be around $4,500.

Is there an industry standard or would laying plywood down be my best option?

Gary Holiday
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    Remove poor slab, dig down, insulate and put in new slab. That way you improve heat losses and increase available height. – Solar Mike Dec 18 '20 at 06:00
  • Any leveling should be able to cope with additional settling. If the slab is already uneven, I suspect that putting (e.g.) self-leveling cement over it is going to result in a bunch of cracks in a few years. You also don't have space for any insulation. – user3757614 Dec 18 '20 at 16:40
  • When it comes to a large area self leveling is more than remove and replace. I am guessing you are asking about the back of the photo with ~ 6 slab segments and huge gaps. I would be removing this and replacing then you only have the seam on the 2 slabs to deal with. I would be looking into the wall below where a window ? Was removed. Sheer cracks through blocks are bad and normally point to foundation issues. – Ed Beal Dec 18 '20 at 16:59
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    @SolarMike That sounds much more expensive than the $4,500 that OP which is not willing to pay for leveling cement. – MonkeyZeus Dec 18 '20 at 18:56
  • @MonkeyZeus and doing the job badly then having to do it again may end up costing even more. Surely pointing out a more than reasonable solution is sensible? – Solar Mike Dec 18 '20 at 18:58
  • You say "without losing height", but then you go on to discuss to options that lose height. Exactly how rigid is that requirement? – isherwood Jan 14 '21 at 14:06

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There isn't much you can realistically do that will make those slabs even: either one has to come up, or one has to go down. I don't know what options are available for mudjacking a slab with a house on top, but if you could even find someone that can do it, I'd imagine both the cost and risks would be.... a lot.

depending on how big the gap is, you might be able to level it with epoxy. There are self-leveling coatings designed to fill gaps and cracks. You could also try using vinyl floor tiles to make the transition more gradual.

Probably the easiest (and cheapest) thing to do would be to get a big diamond grinding wheel and bevel down the lip. It won't make the slabs even, but at least you won't trip over it anymore.

Z4-tier
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  • A 20 amp grinder, and two weeks of asking yourself why you didn't stay in college. [How can I level this concrete floor so I can install laminate?](https://diy.stackexchange.com/questions/26503/how-can-i-level-this-concrete-floor-so-i-can-install-laminate) – Mazura Feb 13 '21 at 23:15
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The easiest and most practical would be to clean slab , put a bonding agent and use concrete with smaller aggregate , im in canada so it would be 10 mm ( .394 of an inch ) You can then pour floor min depth of about 1.5 inches which is not much loss ..You need 4 to 5 yards max of concrete plus pay the finishers should come to about $2,000.00 maybe $2,500 max but i doubt it Then its done , level and looks good ...I really dont think settlement is an issue looking at age of lumber used so further settlement is an non issue

Peter Manson
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  • Quoting pricing is nebulous at best. Pricing varies significantly by locale and gets out dated _very_ quickly. You're best to avoid doing so. If you'll take the [tour] and read through the [help], especially the section on answering, you'll see the standards we try to adhere to around here. – FreeMan Jan 14 '21 at 13:57