I am repairing a tub enclosure and have discovered the previous owner installed a quarter round at the base of the tile wall where it meets the tub because the wall falls short of the tub by 1/2". Not only that, but there is no backing board behind this section, so any mastic applied just disappears down along the wall and tub. I've read about "backer rod" and was wondering if this is something I could use to plug up the space so the mastic has something to adhere to, then replace the quarter round.

Any thoughts,

Thanks

 

Is the tub surround also a shower?

My thought is that if the tub surround also functions as a shower, mastic should NOT be used in this application. Mastic will soften and dissolve when it gets wet.

1/2 inch gap between the bottom of the tile and top of the tub is just poor quality workmanship. If this is also a shower surround, and the installation is tile on greenboard or drywall, using mastic as the adhesive, it must not be too old, or else tile would already be falling off.

 

I sounds to me like you are not talking about 1/2" between the tile and tub, but 1/2" between the backerboard and tub. Is this right? Sounds like the tile is not yet installed. Is this right too?

First, make sure your backerboard is cement backerboard. If not, take it down and replace it. Drywall, even greenboard, is a poor choice for under shower tile. Make sure you have a moisture barrier between the backerboard and the studs.

Then use thinset mortar rather than mastic to mount your tiles (no matter what Dean says). Mastic is a poor choice for showers, since it is not very water resistant. Thinset is not affected by water, and it creates a bond ten times stronger than mastic.

Finally, the 1/2" gap is no problem at all, because the tile will have no trouble at all extending 1/2" (minus the 1/8" expansion gap that you will caulk) past the bottom of the backerboard.

 

I'm sorry I did not make myself clear. Unfortunately this is repair of someone else's work. I do intend to use thinset, the problem is that when the tile was set they only brought the cement board down to 1/2 to 3/4" above the tub, leaving a very large gap and nothing until the greenboard, there is no cement board from where the tile ends and the tub begins.
Any solutions to this problem, anyone?

Thanks

 

Is it cement board or greenboard? We need to know that in order to recommend the proper solution.

 

There is both the green board is attached to the studs. The cement board is then attached to the greenboard and comes down to 1/2-3/4" from the edge of the tub matching where the tile ends.

 

This is a tough one.

Try jamming some fiberglass mesh tape into the back of the space, then put in thinset mortar cement. Apply a thick bead of silicone, and bed your quarter round into that.

Don't use mastic, or anything sold as "pre-mixed mortar", or any product that comes pre-mixed.

Mix the thinset to a very thick consistency. Two or more applications of the stuff may be necessary to prevent sagging of the stuff.

Of course, ripping the whole thing out and starting over might also be a good solution ....

 

it makes for a larger then needed are desired joint however !!!??? You might be able to get a backer rod from a building or home center> Its only porpose is to fill the gap so you dont need so much caulk or sealant. As was mentioned earlier the tile can hang 1/2"unsuported and no one will ever know.