how to install cement board for tile floor?
definitely go down to the sub floor ,either use thin-set as described above or use construction sub floor glue in a tube either large or small i use it quite often and it bonds very well and is a lot quicker than thin set just make rows 8 to 10 inches apart,i recommend 1/4 inch hardy backer board ,you don't want it to be too high to match up to other floors connecting,1/2inch is used primarily on walls to match standard drywall thicknesses,mainly i use roofing nails because its a industry standard and i have a nail gun for them,but if i do it for myself and im not in a hurry stainless large head screws grab very well,you can cut the hardy backer board with a scribe and then snap it ,when im in a hurry i use a die grinder to cut its fast and easy to do curves ,bad side to that is the dust i do it out side or with a big fan in the window and aim at it ,the die grinder can be bought at harbor freight for less than 20 bucks and it also cuts tile
i would recommend removing the old tile first, the reson is that if you install the cement board on top its not really going to grab that well, and when you put in new tiles you are going to have a high floor.intall the cement boards on floor overlapping each board,and before you put it on use a flex bond to adhere cement boards to floor than use screws to hold down cement boards,also make sure that your floor is level,than measure the center of floor and start tiling from there.
If you have a stiff, as in at least 3/4, subfloor, all you have to do it spread a little thinset on the clean subfloor using a 1/4 X 1/4 notched trowerl and nail it down with roofing nails about 12 on center. Roofing nails because they have a large head and are corrosion resistant and easy to install. Then use some thinset and fiberglass mesh tape to close up the joints between the sheet of tile backer.
Your subfloor should be atleast one inch thick after checking that install cement board by screwing it down with 11/2 screws every 6 to 8 inches square.This is the best method and ensures a long lasting bond to the subfloor.I would prefer to pay the extra cost for screws and time then to have to come back on a repair.Also you can tape the seams but since your going over cement board you'll need to use a good mortar and that should handle any movement at the joints .
