John Grabowski wrote:

"Ray K" wrote in message
...
The books stress having the slab flat, grinding the high spots and
filling the low ones. But just how flat does it really have to be?
Can't I just use a little thicker layer of mortar to fill the known
low spots as I lay the tiles, especially if I "beat" the tiles into
the mortar to assure good contact as some books recommend?

Some books and websites also stress the importance of a level slab.
What's so bad about it not being level to within 1/4" per 10 feet?

My slab is at grade.



*It won't be too much of a problem with 4" tile. However if you use 12"
or bigger, the tile will teeter totter over the point between high and
low. Try laying the tile down on a dry run to see how it works out.

If there are dips in the slab, they can be found and marked before
laying the tile. Where there is a dip, just butter the back of the tile
a little bit to fill the void - no teeter-totter. We have 20" tile and
probably minor unevenness - none that were obvious.