On May 16, 10:06*am, "Dante M. Catoni" wrote:

I think you are right about the tile job. No screws were added to the
existing subfloor to prepare it for tile. The ply wood is too thin and
doesn't have nearly enough screws. Now, the Hardiebacker website says
that 5/8" ply is the minimum to put the cement board on top of. Does
that mean if there is nothing else underneath it? So if I remove the
1/2" layer then screw the 3/4" layer to the joists every few inches so
that it is very solid, could I use 1/2" ply under the cement board? I
would still have over 1" of wood underneath the cement board.

Please learn to quote correctly and include the poster's name in the
quote. It makes it easier for people to follow who said what.

You are thinking along the right lines. There are two options.

Remove the crap, fasten the 1x8 perpendicular-to-the-joists boards
securely, install 1/2" plywood with glue and screws, use 1/4" backer
board attached to the plywood with thinset and screws or roofing
nails, set the tile with thinset.

Second option, which may or may not be preferable depending on the
bathroom setup, remove everything down to the joists, 3/4" plywood
screwed to joists (don't glue it to the joists as water damaged
subfloors happen in bathrooms over the years and pulling up a glued
subfloor damages the joists), 1/2" backer board attached to the
plywood with thinset and screws or roofing nails, tile in thinset.

The second option would probably turn out to be a bit cheaper,
possibly faster and has fewer layers with less chance of movement.
The thinset between the backer board and plywood is important - it
prevents any movement and makes the whole assembly one unit.

R