We're about to start tiling a kitchen floor over stripped bare
concrete slab. We're going to be using 18" X 18" tile and we've
started noticing that the floor has quite a few uneven spots in it up
to 1/4" or so. We've heard about leveling compounds but we're kind of
new to this. We already have our cabinets mounted so whatever we use
we need to take that into consideration. Not sure what can be put
down prior to the tile to level the floor better or if something
different can be used to mount the tiles that can take up the uneven
Thanks for any help or suggestions!
1. What was on the floor before?
2. What are these up to 1/4" uneven spots? Are they just small gobs or
saucer size or platter size or what? Or is it that an eight foot straight
edge reveals that, for example, the slab center is 1/4" higher or lower than
I ask because *something* was sucessfully put over the high spots before.
Gobs can simply be knocked/chiseled off; larger high spots could be ground
down. If the floor is smooth but simply higher/lower in the center, just
lay the tiles - you won't notice 1/4" from one side of a room to another.
If the 1/4" spots happen to be depressions, don't worry about them at all,
the thinset will fill them up. Your only real concern is in getting the
edges of each tile flush with each adjacent tile (use a beating board). If
a tile happens to bridge two high spots, use more mortar under it. You can
tell if a tile is embedded completely by rapping it with your knuckles after
the mortar sets up a bit (5-15 minutes)...solid "thunk" sound = set, hollow
sound = not enough mortar.
Use self leveling concrete, if those spots are large, or even if the
whole floor slopes 1/4" from one end to the other. A level floor will
make much easier installing cabinets, for example.
We already have our cabinets mounted so whatever we use
Ouch! Are you going to tile around the cabinets? Bad choice, IMO. Will
be a PITA to install or service a dishwasher,for example, and hope
you'll never have to replace one of the bases. Also, probably you'll
have to make more tile cuts to fit the profile of the cabinets.
Again I would use self leveling concrete, and would consider removing
the cabinets and covering the whole kitchen floor with tiles .
If there are only a few lower spots you could just use more mortar under
the tiles there, but there is a potential risk to leave air pockets if
you're not careful.
The floor just needs to be flat, not necessairly level. For all we know
both ends at opposide walls are down an inch. Hope not.
I've never used self leveling concrete. I've used those floor levelers
in bags. Expensive stuff.
There is also Henry 547 Patch and Skimcoat. Not self leveling but same
type of material as the floor leveler I've used. Floor leveler if I
recall was much more expensive than the patch & skimcoat. The 25lb bag
of patch & skimcoat runs about $22 at the Borg here. One bag covers 40sf
at 1/8" thickness.
Not a lot of work time with these products. Maybe 20 min. Depends on
actual mixture, temp, humidity, etc. One thing I've done is to make the
mix with refrigerated water to extend work time a little. Although mixed
with water, setting appears to be chemical and not evaporation. You'll
be working with it then suddenly in a few minutes it's no longer
workable. About an hour after that it's hard as a rock and you can walk
on it no problem. Next day it's light grey.
How does the self leveling concrete compare to this I'm curious?
Well, may be not everybody sees a need there, but I would have a strong
I've never used the expensive stuff you mention, so not sure how
compares. I am overly simplifying but with SLC you just pour and let it
settle. Gravity will keep the surface smooth and at the same level.
Not sure if you know any of this but I'd be curious:
How expensive is the self leveling concrete/cement?
(bags/buckets? - Coverage?)
Where can it be got?
What's the thickness range?
(the stuff I spoke of was from feather edge to 1".)
And grout up agin 'em, and have a naked grout line.
The advantages of setting cabinets on the finished floor are many, a
more finished appearance being one, but maybe a fine point few would
Without knowing the degree of evenness I can't offer a suggestion, but
I'd guess a real tilesetter could probably just level it out with
thinset as the tile goes down.
Tile on slab is a rather permanent thing, or can be if you remember to
dampen the slab first, I'd be sure I've got the tile I can live with
for a long, long time.
Oh shit, he said 1/4 inch or so. In that case just level it out with
thinset and check it often and wide with 4' or better level. If you
get one a little high just beat it down into the mud.
surface of the concrete? How
many is "quite a few"? Any deeper than 1/4"? It helps to give advice
if we all understand what
you are talking about......cabinets are "mounted"? That means
"installed"? What is size of room,
numberof dips, size of largest?
If the "uneven spots" are globs of adhesive, then we are talking about a
We had tile installed by a contractor, 14" porcellain, on slab. When
faced with making the tile
floor meet the same level as terazzo in adjacent rooms, the contractor
simply put the thinset
on thicker, so it raised the tile on one edge and sloped ever so
slightly. It amounted to making
the thinset 1/4" thicker at the joins, but it is absolutely
undetectable. I was very apprehensive
when contractor proposed doing this, but they did a great job.
The problems I see presented most often about tile are: batches of
colored grout turn out to
be different colors, grout haze dried on tile, what sealer to use.
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