I was planning on using Hardie Backer, but the instruction state that Hardie Backer is not designed for use over concrete. I need to raise the finished floor height about one inch to match an existing floor. If I can use cement backer board, do I use thin set to attach the backer board to the concrete? If I can't use it, what are my options?
I think that would work to attach it using thinset. If it were a wood subfloor, you would attach it with deck screws. But, you should then use a leveling compound over it to level it all off and give the thinset that holds the tile something to adhere to. You should also put a slipsheet over the leveling compound. That will allow the tile and the concrete/hardy backer to expand and contract at different rates, which will prevent tile and grout cracking due to thermal expansion.
I have done it for a fireplace hearth, wanted the tiles up a so they are more even with the carpet so put down some 3/8 inch hardi backer with some thinset. I used mastic on the fireplace though, its just so much easier to use. Been a year now, so far so good. Just make sure you use thinset instead of mastic over the concrete in case of moisture wicking up from the concrete.
How To Fasten Cement Board
Putting down backer board is a waste of time and money when going over a smooth cement floor. Backer board is used to stiffen up an existing wooden floor or wall. It can also be used when planning a shower to allow for build up to slope to a drain. As far as sweating is concerned backer board will not prevent it if it is a problem. It will just make your floor thicker. The sweat comes from the air contact with a cooler floor surface it is not from water seeping through the floor. A dehumidifier will help to solve this problem in the summer months. Make sure you use a sufficient base of thinset (1/4 inch trowel minimum, 1/2 inch if uneven or rough spots). Mixing a latex additive to the grout is also a good idea in below grade and outdoor grouting situations.
No .. The only way to build it up to even think about it is to use a thin set under a cement board,and using that much thinset it doesn t have the compression strength . And you cannot properly attach a cement board to cement. Best way to achieve this is to use a mud which is basically using cement to make another floor. You ll need lathe , portland cement and sand . The sand and cement in the proper ratio and mixed to a special dry consistency is then used to make another floor over your slab. Special tricks and method to do this. Care must be taken when doing this over a slab. Any questions you can e mail me through my avatar and check my qualifications there. GL
