I’m renovating an old bathroom where the old cast iron tub is to be retained. The tub does not sit square in the alcove, and I’ve firred out the studs to overlap the lip around the tub with J-channeled greenboard. The greenboard will be finished with a tub surround. I’m still concerned with potential leakage, as there is a 1/8″ gap between the tub lip and the firring in opposite corners of the tub. Has anyone ever tried flashing a tub to prevent leakage?
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Replies
I think most people flash their bathtubs regularly.
;-)
"A completed home is a listed home."
I'm confused. Is this a one piece tub surround? Is the tub surround going to miss the tub by 1/8" (and therefor a gap between the surround and the tub)?
It's an old cast iron tub. I'm installing greenboard around the tub prior to installing a 5 piece surround around the old tub. The problem is, is that even firred out, there are places around the tub where the drywall is not fully over the 1/4" lip of the tub. I thought I would put aluminum flashing between the studs and drywall so that the bottom edge of the flashing rested on the tub lip under the drywall. All this is mute, if the surround doesn't leak, but I don't want to take the chance and get called back to redo the wall. I've never heard of anyone putting flashing around their tub, so I thought I'd ask before I unrolled the aluminum.
Thanks
Somebody had posted something simular to this just a couple of days ago. I provided a pretty detailed response to that post and I'd hate to repeat it. There might also be some other information in the thread that you'd find to be helpful. It's under "Construction Techniques" and is titled "Bathtub surround caulk".
BTW-hold the green board 1/4" above the surface of the tub. Any moisture that gets behind the surround will wick up the cut edge of the board. The gap will help prevent the wicking.
Edited 10/16/2002 10:54:55 AM ET by Tim
Is the drywall on yet? You could put #30 tar paper across the studs so it laps over the tub flange and then put your drywall on. Any moisture that passes the drywall will run down the felt over the tub flange keeping it out of the wall.
Richie
Do not put drywall on the walls in the tub area it will fail. Use cement board.
John,
I agree, cement board is better around a tub but since Nick said he was using dywall I made reference to that in my post. However, I must say I have seen a lot of these fiberglass tub surrounds put over drywall (and bare suds for that matter!) without a problem. If done correctly, they are good at keeping water where you want it...in the tub.
Richie
I guess he stated a 5 pc tub surround and I assumed it to be one of those glue on kits rather than a fiberglass rigid unit. If it's a rigid kit then you are correct, if it's a glue on kit I wouldn't use drywall behind it.
Instead of aluminum, run tar paper over the studs and seal it to the edge of the tub with roofing cement. I also seal the seams in the tar paper as well as the over the staples. Then run your board over that, holding it 1/4" off the surface of the tub. This gap is then sealed with 100% silicone. I agree to use cement board instead of drywall, because any water that gets behind the surround will wick up the drywall and rot it out. While CBUs will wick water as well, since they are unaffected by water, if you have a layer of tar paper between the CBUs and the studs, you at least have a little protection before the leaking starts. This of course is assuming that water manages to get past the tub surround.