Installing Hardiebacker Cement Board
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I swear this project has been going on FOREVER! The husband finally agreed to let me hire someone to lay the tile and he is doing all the prepwork. Tile guy will be here Monday!
We have screwed down the second sheet of plywood to the original subfloor and now just have to get the hardibacker down. Bill has already assured me that it is necessary to put the hardibacker in a bed of mortar, so we are planning to do that. Here are the questions.
-is it OK to screw the hadibacker down while the mortar is still wet? -when is it OK to walk on? -any tips on cutting the stuff? I already vetoed the idea of buying $250 shears for just this one job and got him a carbide tipped knife.
There are a lot of cuts, so there will be much swearing.:) Any help or advice would be much appreciated! So WHY does my tile installer says that is is NOT necessary to put thinset under the hardibacker? He says that since we put down the extra sheet of plywood on top of the subfloor that the thinset is not necessary. It took ALL DAY to cut the hardibacker for the hardibacker for the project and my husband (who had orginally planned to use the thinset as advused) has now decided to go with the installer's advice and is planning to just screw the hardibacker to the plywood. Please tell me what the dangers of not using thinset b/t the plywood and hardibacker are. I have until about 10am PST to convince him! In case it matters, the tile is 20in porcelain.
You just tell him it is absolutely necessary and this is not an option. I lay tile and hardwood for a living and I see with my own eyes what can and will happen if you get lazy and forgo using the thinset underneath. Go by the instructions on the Hardibacker. I have a feeling you are going to have a problem with both these guys. Make sure you buy Durock CBU tape and have it there. Give it your tileman first thing Monday morning and make sure he tapes the seams as he goes. Taping is not optional either.
I have a bad feeling about your tile job. A 20in tile requires a very,very flat and stiff substrate or you will end up with lippage everywhere. One person installing both the Hardibacker and tile is a better way to go. They will both be blaming each other for a lippage problem if it happens. Good luck to you. 'Please tell me what the dangers of not using thinset b/t the plywood and hardibacker are.' This is simple.
The backer and hence the tile will be installed contrary to the manufacturer's express installation instructions and hence will void any and all warranties. Thinset is necessary under concrete board to: 1)Level the floor 2)Keep the concrete board and screws stable during expansion and contraction of the wood subfloor due to humidty changes 3)To eliminate future squeaks or softspots in the backer than can result in cracked or loosened tiles.
Not using thinset under concrete backer is just plain WRONG and will lead to a failed tile job. The saga continues. Husband spent all day mortaring and only got 1/3 way done with the 400sf area. Turns out the screw gun didn't work well, so he resorted to nailing.