Laying ceramic tile... Do I need to level this floor??

[Al Kondo]

I am in the process of laying 12 inch porcelain tile in both my kitchen and living room. As both rooms are connected, I am laying the tile in both rooms. I finished the kitchen and it turned out great. Because it had a plywood underlayment, I used cement backerboard as a base for the tile. My living room has a concrete slab. I have removed the vinyl tile that was on it and cleaned off all of the glue residue. Here is my question: I have used a four foot straight edge to determine if there are low and high spots on the slab. While most of it is perfect, there are spots that are from

1/16th to 1/8th of an inch low. Can I expect that the mortar that I am applying with a trowel that has a quarter inch notch will take up this small imperfection.... or, should I get floor leveling mixture to level the floor? I would appreciate thoughts.

Al Kondo

[SQLit]

Your good to go. Keep checking the level to you established grade.

[Paul Franklin]

That won't be a problem at all. Most slabs are a lot worse. Just keep checking level as you lay the tile and if you hit a low spot, just add a little more thinset under those tiles.

One more point: If it's not too late, don't straddle the transition between the two subfloor surfaces with a tile; it will almost surely crack after a while. Ideally, you should have a joint over the transition point, and use color matched flexible sealant for that joint line rather than grout. Smaller tile are more forgiving, but the big ones will crack if there is any uneven movement underneath.

Good luck,

Paul