JB,

Thanks for the feedback ... I also ended up calling the company's
customer service. The first answer I got was to let the backer board
hang over the lip. When I mentioned that the shims would have to be 3/8
inch the service rep told me I could let the board end above the lip
and use no shims. Using shims would mean using them top to bottom, on
all studs in the bathroom. And who wants to do that.

Thomas
jbh wrote:
I had the same problem. I use the 4mil (?I cant really remember the
thickness of the poly off the top of my head?) poly as a vapor
barrier
behind the backer board and used copious amounts of good silicone
adhesive
to adhere the poly and then I used thinset to fill the gap between
the
backerboard and the top of the tub (being careful not to let the
thinset
protrude past the vertical plane of the backerboard.). I then let
the tile
hang down over the small gap and used the standard bath tub tile
caulk to
seal the joint.

I tried to use the tar paper for the vapor barrier as recommended by
several
books and helpful borg folks. But I found the corners much too
troublesome
to do right by myself. Not sure if having an extra pare of hands
would have
really helped though.


not sure bout the rest of your issues, the back side of my tub rested
on a
couple of braces, no need for nails through the rim or shims.


Hope this helps
jbh

wrote in message
oups.com...
That's exactly the problem I'm facing now. I'm redoing my 5x8
bathroom
and installed an Americast bathtub, which is about 3/8 inch thick
all
around, also at the lip. I can't fathom how I would bend cement
board
that far out from the studs (even though that's what one of the
guys at
the place where I bought
the tub suggested). It wouldn't match up with the rest of the wall
and
getting the tiles in the corners right would be difficult. So I'm
leaning towards letting the cement board sit on the lip.

On the other hand, the tub instructions say to nail the tub against
the
studs with roofing nails to hold it in place. Makes sense. They
also
say to put a shim on the other side of the nail. Makes sense as
well.
However, the shims would have to be 3/8 inch thick as well, if they
should serve any purpose, and then they'd be in the way of the
cement
board which should be resting on top of the lip.

What should I do? Should I make cut outs in the cement board for
those
shims? Should I carve away that 1/8 of an inch from the cement
board
where the nail will be and so to speak use the cement board as the
shim?

Sorry for asking this stupid question, but I want to do it right
and
not twice.

Thanks,

Thomas