No offense taken, Buzz. Just kidding around.

I sometimes forget about the different climate you fellows have up there. Nobody uses the foam board around here since we don't have the extreme cold for extended periods like you fellows do. It's in the mid 90's here right now, and we've had a pretty mild summer compared to the last few years. When is someone going to invent a hat with a built-in cooling system?

Hello,

This is a question about the shower curb.

As I’ve mentioned, I’ll be using the Kerdi pan, membrane and drain. I’m now debating on what to do with the curb. The floor substrate is above grade concrete slab. Also, I’ll be using a swinging door as the entrance to the shower.

The two option I see are to either use 3 stacked 2x4’s or the Kerdi curb. I sees pros and cons to both approaches – some of it has to do with me being a newbie.

1st method. wood - I’m concerned about wicking into the wood curb from the concrete. But, I’m also worried about not doing a good job in that I’m not sure of the steps. From what I’ve pieced together the procedure would seem to be: 2x4s go directly on top of and make contact with concrete; wrap membrane around 2x4’s but not underneath; wrap a wire mesh around the membrane; nail mesh into place; mud curb so that it comes out flush with the drywall on either side of the curb on both the inside and outside of the shower. What kind of mud should be used? Are these steps incorrect?

2nd method. Kerdi curb. I seem to be somewhat lucky here as I’m anticipating the finished walls, where the shower is to go, to be about 58 ½ “ apart. My biggest concern here is whether it is possible for the curb to come undone from the concrete slab with time? The curb is only held in place by mortar.

Would I be making a mistake by going with the Kerdi curb option in my situation?


Thank you.

In John Bridge's book on Kerdi, he mentions problems he had with moisture wicking from the concrete into the 2x4 curbs he made since he wrapped them tightly with Kerdi. If I remember correctly, he now simply lays brick as a curb. I've used 2x4 every time, and never had a problem, but it doesn't mean I never will. You could try putting a piece of felt paper between the curb and slab, and securing the curb to the door jambs. I would use three 2x4's, securing each one as you stack it. You will still want to wrap the curb with something to attach the kerdi to, such as a CBU or drywall. Kerdi is not supposed to be attached directly to wood.
The Kerdi curb is always an option, I've just never used it since it's easier for me to cut a 2x4 down to size. Also, something makes me think the Kerdi curb might not be as sturdy.

Thanks for the response Kman.

I did some further investigation and ended up purchasing the JB book. Further to your point regarding
attaching Kerdi to wood, he says that framing lumber doesn't provide a good bonding surface for
the membrane. I've also learned that Kerdi curb should be attached to concrete using unmodified thinset and that the curb cuts without difficulty.

Thank you.

Hello,

Just some questions regarding the outside walls of the shower in the bathroom.

1. Would it be ok to not use moisture resistant drywall on the non-shower walls if I go with full wall tile wainscoting?

2. Would there be any benefit to using Kerdi membrane in behind non-shower wall tiles over either regular drywall or moisture resistant drywall?

3. Am I correct in assuming that the bathroom, non-shower, ceiling will need moisture resistant drywall?

Thank you.

In my experience, drywall is drywall. If it gets moisture, I use Kerdi or Redgard and thinset (as opposed to mastic). If you think the area you are tiling is going to see significant moisture for whatever reason, paint two coats of Redgard on it. You could go with a CBU, but if it's already got drywall, then Redgard would be cheaper. A proper exhaust fan will take care of most of the condensation, so in my house, I have the fan positioned just outside the shower, and I never have any significant condensation on the walls or ceiling (just on the HVAC vent once in a while). Use a good quality ceiling paint and that will retard any moisture from wicking into the ceiling.

Thanks Kman. Got it.

I phoned Redgard and had a pleasant conversation.

I’ll have to decide how much wainscoting to go with in the bathroom. My thought is to go full wall, but I’m not totally sold on that yet. Any thoughts?

Back to Redgard. He indicated that Redgard is to be kept down 1 inch below the wainscoting and is not really appropriate for painting over. He suggested, as you did, two coats. Also, he recommend starting off with a primer, 4 parts water to 1 part Redgard. Tile is to go on with modified thinset.