Kerdi at tile flange of tub

[Glen 71]

I'm planning a bathroom remodel to install an acrylic whirlpool tub (Kohler K-1630) in a 3-wall alcove on concrete slab. As this will be combination tub/shower, I am ordering it with a tile flange. I will furr out the studs flush with the flange and cover with drywall and Kerdi, then 4" porcelain tile using Kerabond thinset.

My question is how do I finish off the bottom edge of the Kerdi membrane at the tub? Do I just trim it the same length as the drywall (which will extend below top of flange), or wrap it over the edge of the drywall and glue it to the tub flange?

This is a great site! Thanks.

[Glen 71]

Btt

[Mike2]

Glen, stop the wallboard short of the tub so the membrane can be lapped onto the tub flange. There it can be secured very nicely with thin-set. Kerdi-Fix will work as well but thin-set's a lot cheaper.

[Glen 71]

Thanks, Mike. I assume the first row of tile can extend below the drywall to hide the Kerdi but leaving a gap at the tub for silicon caulk?

[river-wear]

Yep, that's the way to do it.

[Mike2]

Michele's got you covered, Glen.

[Glen 71]

Thanks a bunch!

[Glen 71]

Oh! One more question. If, as suggested, I stop the drywall short of the tub's tile flange, can I omit furring out the studs to be on the same plane as the flange? Thanks.

[Splinter]

Correct-a-mundo!

[cx]

With a Kerdi shower that wouldn't scare me, Glen. I think I'd want some KerdiFix to pookey the Kerdi to that tub lip. It's expensive, but so is most everything good, eh?

My opinion; worth price charged.

[Mike2]

Sure, you can omit the furring strips providing your wall tiles are large enough. I'd say minimum tile size to bridge than gap and still have enough surface area for a good bond to the wall would be in the neighborhood of 4", with more being better.

Yep, Kerdi-Fix would be good too. However if you look at page 32 in John's Kerdi eBook, he still recommends using thin-set.

[Duckman]

if your drywall is 1/2" and the tub flange is only abou 1/8" then you'll have a 3/8" gap between the tub flange and the kerdi, correct? isn't that a pretty large gap to have filled with pookey?

[Glen 71]

Nick,

According to the tub installation instructions, the flange is 1/4" thick. I planned to bring the Kerdi over the end of the drywall and seal to the face of the tub flange. The 1/4" transition doesn't seem to be much of a problem to me, but I've never done it before either! I assume that back-buttering the bottom of the first course tiles a little thicker will mostly fill that gap.

[Duckman]

hmm.. ya, my flange is 1/4" too... i guess that isn't going to be a lot to deal with then.

[Glen 71]

Same project - new question:
In the interest of time, I have decided to hire a contractor to install the tile both around the tub and on the (concrete) floor. I have demo'ed the tub sorround back to the studs. Is the installation of the substrate (HardiBacker) commonly done by the tilesetter, or by someone else?