Backing board and the lippy Bathtub


Old 07-04-03, 09:15 PM
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Question Backing board and the lippy Bathtub

We have had a bathroom torn apart going on 4 years now and we have finally got to guts to start in again. We installed a jacuzzi tub that is not a "set in", but looks like a standard tub. It has about a 1 inch lip going around the perimeter of the tub which also follows down the two front sides to the floor. When we put the backing board up, are we supposed to put the backing on the wall such that it sits on the lip, or are we supposed to cover the lip with the backing board? If we put it on the lip, the backing board will not be flush but will overhang some. If we put it over the lip, we will need to build up the wall a little. We just want to make sure we do this right. Either way presents problems, we just aren't sure which one we need to tackle. Any help would be appreciated.

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Old 07-04-03, 11:22 PM
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Bring the backerboard down to, but not over, the lip. When you tile, the bottom row of tile can cantilever over the bottom of the backerboard to cover the lip. Then caulk the final gap between the bottom tile and the tub.
Old 07-05-03, 07:57 AM
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if you do as john suggests then you need to make sure you put mortar on the back of the tile to support the part that is overhanging or it will break.You can use furring strips to build the wall out a little and then run the backer bord down over the lip
Old 07-05-03, 09:22 AM
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First put a plastic moisture barrier across the studs. and hang down into the tub.

You want the CBU over the "flashing" lip, but not down on the tub. Leave a 1/8-1/4" weep space under it and the tile you set on top. After CBU installation run a razor blade under it to cut the plastic moisture barrier, so it doesn't hang out, then set your tile.
Old 07-05-03, 07:21 PM
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the moisture barrier in this situation is not needed only in showers that are part of steam shower then the moisture barrier is put on the outside of the c.b.u. so you don't puncture it with all the nails or screws you will be putting in to it.Install the c.b.u.using the fur strips and allow to overhang the lip screw about every 4 to6" on the studs,make sure you have the seams on the studs and nail them every 2",once fastened take nylon mesh tape and thin set and tape the seams and corners and take the flat side of the trowel and a little thin set and smear the thin set over the tape and allow to dry

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