Hi -
I am preparing to put a ceramic-tile floor in a 4-season porch, which has dimensions of approximately 17 ft long by 6 feet wide. This porch was apparently an add-on, built some time ago by the original owner. The flooring that was there (I just ripped it up) was carpet-over-pad-over-vinyl tile-over 3/4 plywood-over-sheet vinyl-over-tar paper. All of this was on top of 1X8 pine boards that are laying on the joists. The joists run lengthwise, and are unfortunately on 20-inch centers (like I said, the guy did this himself). What remains right now are the 1X8 pine boards on the joists.
My plan was to screw down a layer of plywood of some thickness, then put down 1/2-inch cement backer board on top of thin-set mortar, and tape all the seams.
The question is when I go to lay down the plywood, what thickness should it be? I ask this because I know from reading that the subfloor under tile should be at least 1-1/8 inches thick, and this includes the thickness of the backer board.
An additional question: is the subfloor thickness measured from the top of the joists to the top of what's laying on the joists? If it is, then do I already have 3/4-inch subfloor already there, due to the thickness of the pine boards?
The thickness of the floor is of concern because if the top of the tile gets too high, I wont be able to put a door mat or runner at the inside of the back door, which leads into this porch.
Long-winded question, but if you can make it through, I would appreciate any help with this.
Thanks very much,
DaveRead More