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GeekBoy
 
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Default Can Cement Board Be Used Between Subfloor and Bathtub?

Also cementboard. You take everything out of the room, screw down
good 3/4" ply, then apply flexbond mortar and screw down 1/2"
cementboard on top of the plywood&mortar with cement screws (remember
not to align the seams the same way you laid the plywood). Now your
floor is all one level, and all cementboard. Place the tub on the
floor with wood stringers on the wall(s), or whatever you prefer.
Insulate the walls and staple 4 mil plastic to the shower/tub area
studs. Some people use tar paper, like you use on a roof. Screw 1/2"
cementboard to the shower/tub stud area, leaving 1/4" gap on top of
the tub so it's not resting on it, and greenboard everywhere else in
the room walls, including the ceiling. Fill the tub with water to
weight it down and caulk the 1/4" gap you left between the cementboard
and tub. Since a regular tub is 30" deep, I like to use cementboard
at 36" deep and all go around the tub with cementboard/caulk, just in
case water drips out of the shower area. Let it dry and drain the
tub. Lay your floor tile, again leaving 1/4" space back from the tub
and 1/4" above the tub when you do the walls too, just like you did
the cementboard on the walls. Caulk that gap when you're done. Tubs
move around -- you don't walk grout there. Remember, most steel tubs
come with a "lip" around the three sidewalls. You want to put the
cementboard and tile ON TOP of that lip so water rolls down INTO the
tub, not behind it. Yes, the tile will be SLIGHTLY tilted out just
above the tile if you do that. Don't worry about it. I like to lay
floor tile first, so the wall tile ends up nearly resting on top of
the floor tile (again, with a slight gap). That way, water rolls off
the wall tile ONTO the floor tile, not behind it. The only other thing
I worry about is the fact that 3/4" ply, plus 1/2" cementboard, brings
my floor higher than it used to be. So, when I put the marble saddle
in the door threshhold, someone could trip walking into the bathroom.
You can get attractive wood step-up saddles, easily stained/poly'd to
the color of the floor, however, and this works nicely in front of the
marble saddle.
I'm no expert, though.


(e patashnikov) wrote in message . com...
From what I've read, cement board is placed between the plywood
underlayment and the floor tile in the bathroom. What is placed
between the subfloor and the bathtub?