Another double check re: ceramic floor tile install

Tile setters are telling me variances to slight variances (1/4" or less) in concrete floors are common...that i can believe. The question is can those out of level/hi ,low areas in the concrete be made up for by trowling out a bit of extra thin set in those areas, so the tile sets level?

Thanks all!

Yes, if you use the right thinset. It is harder to do at tile setting time, but is doable. You can use regular thinset up to 1/4" thick and screed it flat first, though, if you wish. Let that cure overnight, then start out with a flat surface. Most pros wouldn't waste the time, and would level as they go. It takes more skill, so depending on who's doing this, and if you want to do the prep yourself, try flattening it first. If the total thickness of thinset is much more than 1/4", though, you are better off with a medium bed mortar (often called granite and marble), since it has more sand in it and can be installed in a thicker bed without the tile sinking. Thinset is meant to be installed in a thin layer...medium bed can be thicker.

double check re: ceramic floor tile install in kitchen

Jadnashua, Ultraflex 2 professional grade thin set mortar with modified polymer additives by MAPEI will be used. Would this be considered a right type of thin set you were refering to ,for the application desired with level variances in a concrete floor?

yes.

all thinset are good for this. there is no thinset that is not appropriate for this. Any other thinset is also good. The cheapest thinsets have no polymer; you don't need the polymer for this goal to bond to the slab and fill space, unless there is a reason the tilesetter is aware of that I am not aware of.

the idea that you could mix some thinset yourself and fill in the depressions is a good thing to do. Even though tilesetters can do some of that along the way, it is much better to do a large part of it in advance for them. You won't do a perfect job, but you will help them by giving them a better starting point. Then, the maximum variance might only be 1/8" and only across smaller areas.

if you do it yourself in advance, you will ensure that the tilesetters pay attention to getting the flattest floor possible instead of trying to compensate as best they can which may produce a seemingly flat floor that isn't in reality very flat. When a floor isn't all that flat (but looks it), you might find that opening a door all the way makes it bump against the floor tile, far back from the tiles closest to the door sill and frame. Other little problems can also arise.

david

Why not self-levelling cement?

It's more expensive than thinset, but a lot easier to get a dead-level surface. I think there was discussion of it here, but you could also check the John Bridge tilesetters forums for details.

floor

You can almost depend on two things when concrete is poured.
1. The area around the toilet's pipe will be uneven, and possibly higher than the surrounding area.
2. Floor drains will almost always be higher than the surrounding floor.