"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.