how do i seal up this bathtub!?!?!?

My sister is moving into a new apartment, and asked me to make her new bathtub deeper. i built a small wall out of redwood 2x4's with a good coat of uerathane on them, and the wall itself should be good and watertight, but the joint between the redwood and the bathtub is proving next to impossible to make watertight. i can't screw into the tub, for obvious reasons, so i have used two different types of caulk, a sealer strip made for replacing caulk, and i am not sure what to try next. i am getting really frustrated by this project, so i am wondering if anyone here has any suggestions on how to make a good watertight seal between redwood and a fiberglass tub. can anyone help?

caitlinsdad8 years ago
You should use 100% silicone caulk in clear or whatever color would match your tub. I think the joint will still fail at the wood part as it will peel away as the wood would still suck up moisture from the back in a humid environment like the bathroom. You should look at your design and have a flashing under and behind the joint to act as a "waterfall" diverter for any splashed on water. It could be a strip of L-shaped plastic that you caulk to the tub and the wall. The redwood could just hang a little bit higher than the tub and the joint would allow it to dry out after a bath. Make sure you waterproof the exposed bottom of the wood. Good luck.
ran5045 years ago
Trying to increase the depth of an existing tub is a bad idea. There is no permanent way to do it without damaging the existing tub. If permission to modify the tub has not been granted by the landlord, you could potentially be evicted. Other issues that can occur are growth of mold and mildew, wall damage and floor damage from leakage. Also if the water level is too high it can contaminate the water supply by creating a cross connection.
NachoMahma8 years ago
. Most RTV "caulks" (eg, L's aquarium sealant) should work.
lemonie8 years ago
Aquarium-sealant? But like the screws you'll probably find that it leaves permanent traces on the tub. L