[JA Boomer]

Hi,

I am about to start my first Kerdi project.

Couple of questions. First, the Kerdi shower valve seal.

My shower valves have check stops on either side of the valve.

So the Kerdi valve seal isn't going to fit around my shower valves. I assume I can just run my Kerdi membrane around my shower valve and rely on the gasket or a silicone ring around the shower valve face plate to keep water out?

Second, I wonder if layering Kerdi from bottom to top is acceptable, or even preferred? In typical Kerdi instructions, I see that the Kerdi band applied in corners is applied after the walls and pan.

Consider the bottom corner between the shower wall and pan. If you applied Kerdi membrane on the pan, then Kerdi band on the pan/wall corners, then Kerdi inside corners, and then Kerdi membrane on the shower walls, your Kerdi system would be layered so that water would never hit thinset on an upslope. Every transition would be Kerdi to Kerdi to the drain whereas the typical installation method would leave a thinset "lip" at the wall corner where the Kerdi band starts. Any thoughts?

Thanks.

 

[chandler48]

IMO, you will be spending a lot of money for little return. You already have Durock on the walls which is an acceptable substrate for tile. Applying Kerdi won't gain anything. Yes your valve hole in the Durock is surgically too small. It should have come with a black spacer which would give you the proper dimension for the hole in the wall to where the trim will fit.

 

[JA Boomer]

Yes, the "mud box" left little room for error to the gasket ring on the valve face plate, so I made the hole smaller to make sure the tile around the shower valve will have as much backing as possible. I know Kerdi might not be strictly necessary, but I'd rather have a waterproofing system vs only a substrate that won't disintegrate with a little water exposure. Both is better, IMO. This is my home, and I plan to live here for a long time. I've got many other rooms to renovate, and I don't want to be back in here fixing a problem anytime soon.

 

[chandler48]

This is my home, and I plan to live here for a long time.

Of course it is your choice to do what you feel best. We're here to give advice to questions asked. You need not worry about tile support around the valve. You will need to open the hole up more or the trim ring won't fit properly. I asked about the plastic trim ring template and protector. No answer on that yet. It should have been left in place to give you the proper opening at the valve. Red Gard or other sealants painted on the Durock will make the surface more waterproof, and cheaper than Schluter.

All I am trying to do is save you some money and achieve a good job at the same time. Best of luck with it.

 

[JA Boomer]

Of course it is your choice to do what you feel best. We're here to give advice to questions asked. You need not worry about tile support around the valve. You will need to open the hole up more or the trim ring won't fit properly. I asked about the plastic trim ring template and protector. No answer on that yet. It should have been left in place to give you the proper opening at the valve. Red Gard or other sealants painted on the Durock will make the surface more waterproof, and cheaper than Schluter.

All I am trying to do is save you some money and achieve a good job at the same time. Best of luck with it.

So I'm clearly missing something here. A few pictures might help to clarify.

Here's what I understand (maybe you could point out if I've made any wrong assumptions, because it's definitely going to be easier to cut out the cement board now!)

The blue piece, what I've called the "mud box", I thought was simply to protect the valve from thinset / drywall compound during the construction process. I had them on the valves until I hung the cement board. When I was hanging the cement board, I looked at the "mud box" vs the gasket area on the plastic valve ring (see picture above). There wasn't a lot of wiggle room, so I took the "mud boxes" off, cut holes in the cement board to provide access to each valve and the stop checks, and taped the valves with painters tape for protection. This way I knew for certain I'd have tile close enough to the valve for that gasket to seal to.

I am not under the impression, nor was there any instructions that the "mud box" provided a template for the cement board cutout, although thinking about it, that does make sense.

However, you can clearly see where the plastic ring screws into the valve body, and the screw holes are clearly open within the cement board cutout, so I currently don't see any problem. I also believe there's enough space to access the valve body/cartridge and the stop checks.

Do you see anything differently?

Thanks!

 

[chandler48]

You're good to go. It appears the waffle side of the white ring gets the black seal, and goes against the tile, while the pretty gets put on last. You've taped your valve up to prevent thinset intervention. Just keep the area clean.

 

[jeffnc]

I use Kerdi Valve seals all the time with valves that have shutoffs. You cut a 5" hole for the valve seal to fit. The valve should be mounted well to a backer in the wall framing. Putting backerboard right up to it doesn't help anything. The Kerdi valve seals isn't a must-have, but a nicety. Notice if you look carefully that the ring is actually tapered, so that any water that drips is going to either run around it, or drip to the inside of the shower.

Backerboard isn't waterproof, so you should waterproof it with something. I prefer Kerdi myself. But then, I usually avoid backerboard altogether because it's awful, and use Kerdi Board, which has the Kerdi membrane preinstalled.

 

[jeffnc]

Second, I wonder if layering Kerdi from bottom to top is acceptable, or even preferred? In typical Kerdi instructions, I see that the Kerdi band applied in corners is applied after the walls and pan.

Consider the bottom corner between the shower wall and pan. If you applied Kerdi membrane on the pan, then Kerdi band on the pan/wall corners, then Kerdi inside corners, and then Kerdi membrane on the shower walls, your Kerdi system would be layered so that water would never hit thinset on an upslope. Every transition would be Kerdi to Kerdi to the drain whereas the typical installation method would leave a thinset "lip" at the wall corner where the Kerdi band starts. Any thoughts?

It doesn't matter. You're thinking of Kerdi as if it were like the shingles on your roof. Kerdi doesn't shed water that way. It's waterproof no matter which order you install it, if installed correctly. But if it makes you feel better, it's certainly fine to install it in the order you are more comfortable with.

One question I have is how are you even getting Kerdi products without the membrane preapplied? That stuff looks old fashioned. Anything I've bought int he last couple years - benches, curbs, pans - are all orange right from the factory.

 

[jeffnc]

Oh never mind, I thought you were using a Kerdi bench and curb, lol.

 

[JA Boomer]

You're good to go. It appears the waffle side of the white ring gets the black seal, and goes against the tile, while the pretty gets put on last. You've taped your valve up to prevent thinset intervention. Just keep the area clean.

Thanks!

I use Kerdi Valve seals all the time with valves that have shutoffs. You cut a 5" hole for the valve seal to fit. The valve should be mounted well to a backer in the wall framing. Putting backerboard right up to it doesn't help anything. The Kerdi valve seals isn't a must-have, but a nicety. Notice if you look carefully that the ring is actually tapered, so that any water that drips is going to either run around it, or drip to the inside of the shower.

Interesting, I wasn't sure if the valve seal was actually large enough to leave access to the check stops on either side of my shower valves.

It doesn't matter. You're thinking of Kerdi as if it were like the shingles on your roof. Kerdi doesn't shed water that way. It's waterproof no matter which order you install it, if installed correctly. But if it makes you feel better, it's certainly fine to install it in the order you are more comfortable with.

That's EXACTLY what I was thinking. I contacted Kerdi with the question, they said Kerdi band and corners must be installed after the membrane on the pan and walls, so there you go.

 

[jeffnc]

I contacted Kerdi with the question, they said Kerdi band and corners must be installed after the membrane on the pan and walls, so there you go.

Not sure why they said that. I've been to 2 Schluter seminars and they have always said it makes no difference. There might be some other reason they told you that, but it's not waterproofing.

 

[JA Boomer]

Not sure why they said that. I've been to 2 Schluter seminars and they have always said it makes no difference. There might be some other reason they told you that, but it's not waterproofing.

Ya, they just said that's how it is in the installation handbook. I know thinset isn't exactly permeable, but I wanted the eliminate the lip where the wall membrane hits the Kerdi band on the corner. No worries, I'll do it their way.

 

[jeffnc]

Ya, they just said that's how it is in the installation handbook. I know thinset isn't exactly permeable, but I wanted the eliminate the lip where the wall membrane hits the Kerdi band on the corner. No worries, I'll do it their way.

Oh OK, well that's just because it makes more sense to put in the wall membrane and pan membrane first. But like I said I haven't installed that stuff in years - it comes standard with the Kerdi board and pan now.

Anyway, thinset IS permeable. That's why Schluter's technology is interesting. There's something about the fleece in the Kerdi that combines with wet thinset to break the wicking or migration or capillary action of water through that thin layer of thinset. Normally water could go through thinset, but when installed correctly with Kerdi it can't.

Anyway, you're going to have a bit of a lip no matter what. But the Kerdi Band is actually thinner than the membrane so it's not much. It can build up once you put 3 layers together though. If it's in the corner of a shower floor that's not a problem - if anything it helps with drainage. It does get a bit annoying around other places like niche corners.

 

[JA Boomer]

So I guess on the Kerdi shower valve seal, the gasket is 4.5" wide. I'd need at least 5" to provide access to my check stops. So I'll just go with regular Kerdi membrane around the valve and rely on the gasket in the valve face plate for water diversion.

 

[JA Boomer]

I've got another question if anyone is willing. My wife wants tile edge trim where the shower tile meets the drywall. So how far do you run the Kerdi out towards the drywall? Couple options:

1) To the location of the shower glass on the wall - no reason not to go farther in my mind.
2) To the edge of the tile - this means the edge trim will have to go overtop of the Kerdi, and there will be a very small gap between the wall and the trim which could be filled with caulk.
3) Close to the edge of the tile - runs the risk of the trim piece being half on top of the Kerdi and half over drywall, could lead to an uneven placement against to wall, could cut the trim flange to fit.
4) Halfway between the glass and the edge of tile - this way the water protection runs past the glass, but the trim will sit flush against the drywall and your tile will seat nicely because the trim flange and the Kerdi will be close to flush above the wall as well.

Picture:

Seems like Option 4 is the way to go. Have I grossly overthought this, or is there a right answer?

Thanks!

 

[jeffnc]

So I guess on the Kerdi shower valve seal, the gasket is 4.5" wide. I'd need at least 5" to provide access to my check stops. So I'll just go with regular Kerdi membrane around the valve and rely on the gasket in the valve face plate for water diversion.

I use a 5" hole saw both to cut Kerdi drains in the floor, and to cut holes in Kerdi board for the valve seal. I've installed many valves with stops and I've never seen one that I couldn't access with the standard valve seal in place. Remember the seal has rubbery edges that have some give in case you have a tight fit for your screwdriver.

 

[jeffnc]

So how far do you run the Kerdi out towards the drywall?

Yes you are probably overthinking where to stop the Kerdi in terms of tile and trim installation, but you are probably underthinking in terms of waterproofing. (There is really no "risk" of the trim profile being half on Kerdi and half on drywall - the thinset will cover any minor difference in height - just get it flat and leave it.)

Technically, if all goes well, you don't need to waterproof past the glass (lets' just say a half inch past just to give some margin for error.) Any amount you want to go past that makes no difference, even for the supposed "problems" you mentioned. But presumably you have a shower curb there. What I like to do is give extra waterproofing for those outside-the-shower dribbles that you see so often, that cause minor water damage. Or sometimes the silicone caulk used around the glass or glass trim hardware fails somewhere. So really you want to waterproof the outside corners of the shower curb as well. If tiling the floor I use Ditra, and I put a strip of Kerdi Band connecting the bottom of the curb to the Ditra on the floor, before tiling the floor. Along the wall corners I use Kerdi outside corners, or you can use Kerdi Fix caulk or similar polyurethane caulk to seal this. Then simply base how far the Kerdi goes on that. I virtually always bring the tile outside the curb a little bit because I think it's a good look, and it also covers all this.

 

[JA Boomer]

I use a 5" hole saw both to cut Kerdi drains in the floor, and to cut holes in Kerdi board for the valve seal. I've installed many valves with stops and I've never seen one that I couldn't access with the standard valve seal in place. Remember the seal has rubbery edges that have some give in case you have a tight fit for your screwdriver.

So it looks like I will be able to access the screwdriver slot on the stop valves with a slight angle of the screwdriver against the mixing valve seal flange. Do stop checks ever need to be replaced, because that's probably not happening with the Schluter mixing valve seal in place.

 

[JA Boomer]

 

[JA Boomer]

Sorry for all the posts. The back of my valve trim plate is waffled and won't seal to that Schluter flange. I don't see any point in installing the mixing valve seal.

Is it the tile that's supposed to seal against the flange?