caulk between backerboard and shower pan

[lucygi...@aol.com]

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.

[Mikepier]

It would not hurt. The GE stuff would be fine.
But if you tile and grout correctly, you should have no water problems.

[John Grabowski]

<lucygi...@aol.com> wrote in message
news:de1d1b44-9956-4a23...@r37g2000prr.googlegroups.com...

Do it. Not sure what caulk to recommend, but every little bit of protection
helps to prevent water from traveling.

[EXT]

You could use Schluter KERDI to seal the backerboard and the joint between
it and the shower base. An 1/8" gap could pose a tile laying problem when
trying to fit the tiles against the base, doesn't the shower base have a lip
all around that fits behind the tiles to aid in waterproofing the joint?

<lucygi...@aol.com> wrote in message
news:de1d1b44-9956-4a23...@r37g2000prr.googlegroups.com...

[Red Green]

Mikepier <mike...@optonline.net> wrote in news:1fdef5db-d47a-4819-9b52-
a94969...@v15g2000yqn.googlegroups.com:

Even with brand new tubes, before actually caulking squeeze some of the
silicone on scrap. In 30 min it should slightly skin. If it doesn't,
don't use that tube. It will not dry/fully dry. GE silicones are
notorious for it. I got burnt once.

> But if you tile and grout correctly, you should have no water problems.

Well, shit happens ya know.

[Joe]

On Dec 17, 2:44 am, lucygirl1...@aol.com wrote:

> what kind of caulk should I use
> between the backer board and the shower pan?  I think I would use GE
> Silicone II.
>

Many posts in this NG relate problems with GE silicone II. Short shelf
life, failure to cure completely, etc. Personally I can confirm the
problems. The original silicone formulations are still the best. I've
used tubes that have been around the shop for some years with no
difficulty at all. But you may want to consider another high
performance or specialized sealant, because anything the silicone
touches will inhibit bonding of tiles in that area. Polyurethane door
and window sealants are possibilities. Choose wisely and good luck.

Joe

[DanG]

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)
dgri...@7cox.net

<lucygi...@aol.com> wrote in message
news:de1d1b44-9956-4a23...@r37g2000prr.googlegroups.com...

[lucygi...@aol.com]

Thanks very much for all of the responses. For the folks who
recommended polyurethanes over the silicone, why is this? Any
particular reason?

Thanks.

[lucygi...@aol.com]

On Dec 17, 7:03 am, "EXT" <noem...@reply.in.this.group> wrote:
> You could use Schluter KERDI to seal the backerboard and the joint between
> it and the shower base. An 1/8" gap could pose a tile laying problem when
> trying to fit the tiles against the base, doesn't the shower base have a lip
> all around that fits behind the tiles to aid in waterproofing the joint?
>

The 1/8 inch gap was what was recommended on the installation
instructions for the backer board. I guess I'm just figuring since
that piece of tile will not be loaded it will be OK to overhang the
edge of the backer?

The shower base doesn't have a lip, it just goes straight down and
sits directly on the subfloor without any kind of flange or lip.

[Joe]

Read my post on the subject. Silicones are like Pam in a frying pan or
baking pan. Things don't stick to them. A single loose can of silicone
spray has been known to shut down a big factory painting operation in
just minutes. Knowledge of your materials will always get you a
superior outcome. HTH

Joe