wrote:

My contractor has just finished laying Porcelain 20" x 20" tile in our
kitchen and nook area (approximately 320 square feet). Our house is
only 5 years old and the tile was laid on concrete slab. The slab
initially had linoleum on it which was removed before laying the new
Porcelain tile.

The problem was that the tile looked somewhat uneven after it was laid.
After allowing 24 hours to set, we were allowed to walk on it and
could immediately tell by feel that many of the tiles were not level
with adjoining tiles. Using a level across adjoining tiles confirmed
this. I even did a "sliding chair" test where I would try to slide a
chair across the kitchen. The chair would hit the uneven tiles and
stop and tip over. Obviously, this is now a hazard.
As a result, we are having the contractor rip out the entire 320 square
feet and do it again.

It seemed to me that since they were laying tile on 5 year old conrete
slab, this should have been a pretty standard task. Their explanation
for the uneven tile heights was not clear, At first, they seemed to
try and explain it by saying the concrete slab was unlevel, but I told
them that seemed unlikely with a 5 year old slab. Furthermore, I said
they could have leveled it with screed or some kind of leveling
compound fiirst. Then they said that they were trying to match the
tile height with the adjacent room's hardwood floor height by using
extra thinset under the tiles and as a result, some tiles ended up
unlevel with others.

The extra thinset depth should have allowed them to beat down the tile
and get the lippage under control, but there are some issues with the
thickness. How much were they trying to bring up the tile to match the
other floor? If it was more than a pretty small fraction of an inch,
they should have probably gone another route using another
material/method to make up the difference. Thinset is for thin setting
beds.

The height difference between the floor areas could have been made up
by using a self-leveling floor cement and/or using an isolation
membrane such as Ditra
http://www.schluter.com/english/prod...601-index.html
to bring up the floor level.

Part of the problem is the size of the tile you chose. The larger the
tile the less room for error. Any little inclination in the surface
will be magnified, and since there are larger planar surfaces and fewer
joints...well, it's not going to be perfect.

For larger tile and stone installations a thick set (mud job) setting
bed is the preferred way to go. That allows the setter to beat down
the tile/stone into a flat, planar position.

Someone mentioned using a short straight edge to keep the floor planar.
I'd use a longer straight edge of 4' to 6' to insure that you're
dealing with surfaces and not edges.

Many of these things should have been pointed out to you and also
researched by you. The specifications for the job should have been
included in the contract including what amount of lippage is acceptable
and how flat the floor should be within a given distance. Relying on a
contractor to do nice work on something that he may or may not have
experience with, or may or may not meet with your expectations, is iffy
at best. Unless you checked his references for similarly sized tile
installations you took something at face value. That's a guaranteed
losing proposition.

R