The concrete slab in my family room settled resulting in a crack down the
middle and causing each end to sink about 2 inches. I want to make it level
so I can lay tiles. I want to make the floor close to level then cover it
with leveling compound.
My question is: What is the best way to make it "close to level" so I don't
have to use so much leveling compound (which is expensive and not
recommended for thick application)?
Does the rule that concrete has to be 2 inches think apply even if its going
over a slab that is already 2+ inches thick? Can I just pour cement in the
deep areas and maybe throw in some aggregate so I don't use as much cement?
I'm even thinking of burying some extra "Wonderboard" in the deep areas and
cementing it to the floor. Does it really matter how I fill in the deep
areas before I pour leveling compound?
Sure the ends sunk, and the middle didn't heave higher? Is this a converted
garage/patio, or was the room built using a proper perimeter foundation, and
the slab poured inside? Does the high spot move around summer vs. winter, or
dry season vs. wet?
Sorry to be the bearer of bad tidings, but any attempt to kludge the
existing slab will be doomed to failure, unless you fix what caused it to
move in the first place. It will keep moving. At a minimum, you need to get
a mud-jacking company and/or engineer in there, to figure out what happened.
Can't see from here, but from your description I suspect the slab is too
thin and/or wasn't reinforced correctly and/or the site prep/drainage was
Personally, if I was gonna sink a lot of money into a fancy tile job, I'd be
inclined to jackhammer out existing slab, and pour a good one. Unlike tile,
concrete is cheap. The labor to hammer it out and pour a proper slab won't
be much more than the solution you propose, and the end result will be MUCH
I bought this house 4 months ago. It was built in 1980. The family room is
below grade by two feet. A perimeter foundation was poured and then a slab
poured. I had an inspection by an structural engineer. The foundation is
stable. The slab is what shifted and yes the middle of the room is higher
than the ends. I was planning to use the middle of the room as my starting
point for level. I haven't been in the house long enough to know if it
shifts during the seasons.
The structural engineer said it looks like it settled shortly after the
house was built. He theory is that the fill used under the slab was not
Do you think I could level it with cement and then a leveling agent and put
carpet instead of tile on the floor? I really don't want to go to all the
work of jack-hammering the old slab and removing it.
Is the slab entirely floating, or do the outside edges rest on the footer or
a ledge of the foundation like they should? That is why I think the middle
probably came up. But in any case, if your engineer thinks things are stable
now, yeah, you could probably pour another layer of concrete over it,
assuming there won't be any trouble with doors and stuff. Don't go higher
than the the sills of the wood walls (if they go below grade), better to
keep it a few inches below. (concrete should never be higher than wood.) I'd
do a thick enough layer to put 4-inch mesh in it. I'd also go with cheap
(non-glued) carpet, maybe carpet tiles, for at least a full year, and keep
an eye on it, before you consider putting down an expensive floor. Watch for
damp, new cracks, more heaving, etc.
Try a google search on Gypcrete I think it would be perfect for what you
want to do. My friend just used it in three rooms over wooden floors to
level out the floor and he also installed radiant in floor heat in it. It
goes on very thin and is almost self leveling.
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