I would not use silicone. Any of the good polyurethanes would
work well. NP1 is my favorite.

--
______________________________
Keep the whole world singing . . . .
DanG (remove the sevens)




wrote in message
...
Hi;

I'm laying tile in a second floor bathroom. There is an OSB
sub-
floor. I put 1/4 inch backer board (Hardi) down on the
sub-floor and
used thinset and screws to attach it down. I haven't started
tiling
yet.

Prior to this there was just carpet over the OSB sub-floor, and
we had
a small mold issue at the shower; water drips when we open the
shower
door and it soaked through the carpet and got the OSB wet and
there
was some mold growth on the carpet there and the sub-floor.

I cleaned up the mold very thoroughly before laying down the
backer.
There is an 1/8 inch gap between the shower pan edge and the
backer
board, and I'm worried that moisture will get in there as it did
before.

I read somewhere, but I can't find it again, that I can/should
put a
bead of silicone between the backer board and the shower pan to
seal
off the possibility of water getting in there. Then, I'll have
tile
over that, with another caulk bead between the tile and the
shower
pan.

Does this make sense to do? If so, what kind of caulk should I
use
between the backer board and the shower pan? I think I would
use GE
Silicone II.

Comments appreciated.