need bullnose advice

[CarlosD]

Hi,

I installed a Kohler bathtub that has a thick flange (about 1/4") where it attaches to the studs (see photo). Since according to the installation instructions, the drywall needs to fit over these edges, I installed furring strips on the studs and installed the drywall so it fits over the flange. So the new drywall is now about 3/4" above the existing drywall (photo). Looking for ideas on how to handle the tile here since there are no bullnose tiles (mud cap, the kind that bend 90 deg) that are that deep.

Thanks,
Carlos

[Tool Guy - Kg]

Hi Carlos,

That can be a relatively common problem. Most pros will run their tiling substrate down to the top of the flange instead of completely in front of it to avoid the very problem you have. It’s typically not a problem on the back 5’ wall, but can be very problematic on one or both of the 30” wide walls where it joins with the walls outside your tub area.

But before we go too far, I’ll point out that unless you are going to cover that green board with Schluter Kerdi waterproofing membrane, you are probably asking for trouble both in a shorter service lifespan of the tile work and trouble with a lack of code compliance (if applicable in your neck of the woods).

There is also missing wood where the old and new substrate meet each other. The lack of something to join the two together will allow excessive flex when leaned on and may lead to cracked tile and/or groutlines.

Can you tell us what your waterproofing plan is?

[Tiger Mountain Tile Inc]

Hi Carlos, It looks like you're in a little bit of trouble right here.

Right now, that greenboard, the way it is, probably isn't going to work for whatever you want to do.

How about this- Can you tell us what you are wanting to do and how you are building this wet area and we can help get you there.

[CarlosD]

Thanks for the responses, guys. Yes, I planned to use Schluter Kerdi membrane over the greenboard. I havent applied the membrane yet. I could reinstall the greenboard without the furring strips but then it would not overlap the flange. But it would solve the space problem between the two substrates Bubba was referring to. Would Kerdi membrane be sufficient to waterproof the flange joint? I thought of doing that, and actually am doing that on the wall away from the showerhead. But I called Kohler and they said the greenboard should extend over the flange.

[Tool Guy - Kg]

I’d remove the furring strips, add a vertical wood stud or piece of plywood to bridge the new and old drywall, install the drywall flush with the existing walls (and stopping it just above the tub’s tiling flange), then run your Kerdi membrane down over the front of the tub’s tiling flange. Use KerdiFix to adhere the bottom backside of the Kerdi to the flange.

And realize there’s generally more to lose than gain with greenboard. The minuscule amount of temporary water shedding is far outweighed by the coating that acts like something of a bond breaker. Unless there’s a code forcing me to use greenboard, I will never install it. Plain drywall has a better bonding surface.

[CarlosD]

Thanks, will do as you said with plain drywall. Did not know that about the greenboard not bonding well. I had used plain drywall+Kerdi for my other shower project but thought greenboard would be better for added redundancy.

[Tiger Mountain Tile Inc]

I agree with Kurt on installing the wall board above the flange and Kerdi over. It used to be in Kohler's instructions to install above the flange but it looks like they've changed it.

[CarlosD]

Thanks, much appreciated!