Corner shower seat

[jean A]

I had a walk in shower built and tiled which included a corner seat. The seat is made of treated pressure lumber and not built to the floor (free standing seat area made of lumber, exposed to floor). Cement board used but tile has come off entire front of seat...top small tile all tight and in place.
I noticed the carpenter made the front of the seat with a piece of cement board (green lumber under) which has a 1/2 + gap where it joins the flat cement board on for the top of seat area. He filled the gap with mastic and then tiled over. The tile didn't stay on for even a month. Tile was set and no water to shower for over 10 days after installation.
He is coming back to fix problem but I don't think a simple reset of tile is going to fix the problem.
How should gap in cement board be treated? The lumber does butt together well but not the cement board. Thanks for any comments or help.

[bbcamp]

Jean, your shower seat has bigger problems than a gap in the backerboard. First, it's made with treated lumber, which is prone to warping. Second, the frame is covered with backerboard nailed directly to the wood. Expansion and contraction of the wood will be transmitted through the backerboard and into the tile. It doesn't sound like any waterproofing was installed, and the backerboard joints were not taped. And finally, you said mastic, but I hope thinset was used in your shower.

[ceramictec]

the only thing that will help you out is if you replaced
the seat up now with a Noble - Bench or a Better Bench.

[Ken]

I second you using the Noble Bench

[earlyretirement]

Using a noble bench is surely a good idea, less prone to failure. That said, it isn't impossible for a corner frame bench to work, from the master himself:

John Bridge
Mudmeister
Join Date: Mar 2001
Location: Houston, Texas
Posts: 48,963
A frame bench will work fine as long as it's strong and strongly attached to the walls.
I would RedGard the whole bench including the surrounding wall areas up to about a foot away. Fix it so no water ever gets in, and you won't have to worry about water getting out.
******

Things to keep in mind:
all weather wood (what you have) is sometimes wet, and takes a long time to dry out (very problematic to seal)

I would think that using kiln dried framing and sealing with membrane will work though.




__________________

[Ken]

Here is another solution if you don't want a shelf bench that Brian and I linked you to earlier..

Noble Bench -- This is a solid bench and is ready to tile and 100% waterproof.

[ceramictec]

or even a Masonry Shower Bench.