I want to tile all around the bathtub alcove in a bathtub/shower. The previous people only put a small section of cement board, about 2' or less high right behind the tub faucet area. They put regular wallboard in the rest of the alcove, and the same behind the vanity area. Should I put cement board as wallboard in the entire alcove area, or only on the wall that contains the tub/shower faucets, or what it the most appropriate? Should I put green board behind the vanity area? Thanks!
=== cement board in the entire shower area and waterproof that with walls of tile === the green board is to prohibit the growth of mold in the bathroom and if you have gutted the entire room then it is best that you do the walls of the bathroom with green
I didn't use any cement board when I renovated my bathrooms about 10 years ago but I did use green board for the entire rooms because both I and my bf like to take long, steamy showers and the high moisture level in bathrooms eventually penetrates ordinary drywall and permits growth of mould or mildew. So far, my bathrooms still smell fresh.
The best method is to put cement board in the entire tub surround, not just in the faucet area. Steam from showering can cause damage to drywall if there are any cracks in the tile or grout. You can use green (moisture resistant) drywall or blue (moisture and mold resistant-preferred) drywall in the rest of the bathroom. Make sure the gaps between the cement board panels are sealed with modified thinset. You can do this just before you tile.
The reason you want the cement board is considering that it's considered a rigid or static fabric, just like the tile or marble you must set up. You wish to have to put off all flex from the ground. Or else, any weight applied to it, like walking, will motive the slightest flex under your toes. That you may do away with the flex with either thick enough plywood, or concrete board. The one layer beneath your old flooring isn't sufficient. The tile is not going to bend since it is inflexible and static, and so is the grout between the tile, but the grout is a very small skinny strip, handy to break if reasonably bent. The tile will definitely act like a lever when the floor under it flexes, the grout joints between the tile will quit and crack, and finally break out from between the tiles.
