ceramic-tileconcreteshower
We are currently redoing our shower and would like to use float-cement to carry the tile. The wall behind it is a bit crooked, so, to get it nice and level, the float-cement would have to be a bit thick (>1") in some areas.
Is there a maximum thickness that float-cement can have, for example before it starts cracking in ways that could damage the tiles attached to it?
If your tile is not secure, then the backer is not secure either. You will need to gut it to the studs and install water proof membrane, concrete board or heavy hardy-backer to tile over. The window frame must also be carefully water-proofed as well and trimmed out with a moisture resistant material. Get some professional advise on this one, a new tile job is not cheap or easy and be a shame to have a leaky, grout dropping job when you're done.
As far as the type of tile, ceramic or porcelain are similar products, difference being the hardness grade and the type of glazing. Porcelain is always a better choice in my view as the surface glaze is smoother, easier to keep clean and usually a harder grade.(3 to 7) prices can vary wildly, usually again because of the glazing and hardness factors. Designer patterns also effect the cost as well.
Like Greebo says, you want to get back down to the concrete, but I'd suggest that more to have a flat surface to build on top of. To make the job go faster, you can use a power tool. Several would get the job done:
Power Chisel (best fit for the job):
Air Hammer (you'd need a high capacity air compressor):
Demo Hammer (more power than you need, but it could be useful for other jobs in the future):
MC Hammer (don't touch this):
Best Answer
I am not aware of any maximum thickness requirements, only minimum. Many tile setters do not like going over a cement base that is thinner than 1 1/2" for fear of cracking, although there are additives of one sort or another to get it thinner, though not much. To have more concrete on one side or another to account for an existing condition, will not adversely affect the concrete. The concrete needs to be sloped to the drain anyway so no shower water sets.
The concern you have with a thicker concrete base is confusing to me. The only way that a thicker base can crack is to put too much water in the mix, when the water dissipates, the concrete will crack from shrinkage. But the amount of water to be used in that situation is to be only enough to get the concrete to set up. The term used with this type of concrete setting is "dry pack" at least it is what the tile setters called it. The amount of water needed to get the concrete damp enough to stay in a ball when you pick up a handful and squeeze. No squishing, no water dripping. Just getting it damp enough to hold together. With this, there is no maximum, though 2"-2 1/2" is the thickest ever needed to make the base for tile. You could add reinforcing wire to it although I have never seen it done for showers. mainly because of the rust potential, I think. Concrete and galvanized don't get along too well, let alone regular wire mesh with no rust proofing.