OK, I have searched and found lots of debate but very little concensus so before I begin I have a couple of questions for the experts…
I am preparing my bathroom for a tile floor. The house is quite old and I am nervous about movement . The floor currently is 3/4 in plywood on the studs. I plan to put backerboard down but do I need another layer of plywood first? For fastening the plywood and/or backerboard , I think I read somewhere not to screw/nail to the joists as to avoid transforming the movement to the new floor. I also read the opposite, any recommendation?
I want to avoid an additional layer of plywood if possible, too much height. Is the following OK?
Backerboard – Whatever thickness Durrock is. Screwed and glued to existing flooring.
Layer of concrete – 1/8″ over durrock
Tile with thinset
What about a moisture membrane? If I put the layer of concrete, wouldn’t skipping the glue/nail make the floor ‘float’ and avoid transferring movement to the tiles??
I was suprised not to find a ‘recipe’ for tile prep.
Thanks for your comments –
Replies
go look at http://www.google.com then look at Hardee board, or Hardie board. They will tell you lots of stuff on that very subject.
It is not hard to figure out, just a pain sometimes on a redo.
the tile backer is just a tile backer.... what you are trying to achieve is a non-flexing floor..
the joist sizing and spacing should be on the hefty side ...not on the light side.. and most tile experts will tell you they want 1.25" of floor under the backerboard... or even instead of the backer board..
you can get away with a lot of things .. but what would be recommended would be stiff floor frame, 3/4 subfloor, then 1/2" plywood then either tile or backerboard...
but remember.. tile backer will not do anything for flexure
Mike Smith Rhode Island : Design / Build / Repair / Restore
I just finished reading the Georgia-Pacific http://www.gp.com/gypsum site for installing my own floor. I was considering at their DensShield proguct and after reading the info, I am going to use it for the floor in my bath. I have used Hardee Board and found it very heavy and very hard to work with. The DensShield product is almost half the weight and cuts with a box-knife.
As far as adding additional sub-flooring, G-P calls for 5/8" ply on 16" center joists. They specifically recommned NOT nailing into joists. The backer board comes in 4x4, is put down with latex-cement mortar and then is nailed or screwed to the subfloor - full instructions on the G-P site.
JC O'Keeffe