Expansion Joints in Shower Walls ? [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile

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wizardpb
02-25-2008, 05:27 PM
Hi All,

This is my first post here, but not the first time I've been here. I did a bathroom remodel on my house over the summer - both bathrooms down to the studs - and found all your postings and advice incredibly helpful. A huge thank you to one and all, professionals and DIY'ers alike. Tile is complete, but I still need some cabinetry. Will post pics when it's done.

Now I have a problem. I'm doing a simple shower job for a contracting friend, for which I'm being paid. I don't usually do this for a living - I do computer software consulting for that - but I'm 'on the bench' right now, and he offered it to me based on what I did with my bathrooms.

I have done it with Kerdi, which worked great, here are the details: 60x32 rectangular corner shower, stone is tumbled marble pre-sealed, 3x6" 'subway' design. I used a Schluter tray for the base and built the kerbs myself, as I needed a specific size. Mortar is MegaBond. Ceiling was also tiled, as per customers request. (And no, it wasn't pleasant doing that. I still have mortar in my hair :-). Grout is SpectraLock (the Lowes variety).

The issue is with a disagreement with my friend (who's also my boss at this point !) about expansion joints. As per everything I've ever read, I left 1/8" expansion joints at all 90 deg joints - inside corner, base and ceiling - and planned on caulking with silicone and backer rod. My friend insists I push grout (SpectraLock !) into these before I caulk, to seal them, since he thinks the silicone won't stick well to the pre-sealed surface of the marble well enough to seal things properly.

Now, he's an experienced, and very good, contractor (and a very decent guy), so I'm loathed to disagree with him too much, but ... I do disagree. I warned him that doing that could lead to tile popping off as the walls move. I also think that the silicone will stick fine (I've done a test tile to find out), and even if it does leak a little, so what ? That's what the Kerdi membrane is for, isn't it ? Isn't the idea with Kerdi that the shower can get as wet as you want, and will dry out quickly, because the membrane keeps the water away from the substrate (CBU in this case). ?

So who's right ? Maybe neither, maybe both ? I'd really appreciate an expert opinion to help resolve matters.

Many thanks to all,

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jadnashua
02-25-2008, 05:37 PM
Tile Council of North America (TCNA) writes the guidelines accepted in most plumbing codes as to how to build a 'proper' shower. They specifically state to caulk (only) all changes of plane....i.e., no grout. If you're going to grout it, forget the caulk as a surface applied caulk never works well. Unless the structure is VERY stable (say a mudbed, not a typical stud based wall with sheeting on it), it will move and crack in the corners.

You can get color matched caulk in both sanded and unsanded, so the texture and colors are pretty good.

ceramictec
02-25-2008, 06:47 PM
the best way to do it would to use the Schluter - Dilex (http://www.schluter.com/4_15_dilex_ehks.aspx) or caulk like you state.

Schluter-DILEX-HKS features a soft, thermoplastic rubber movement zone that is attached to the profile via rigid rubber grip bars to absorb larger movements at floor/wall transitions and at inside wall corners.

Splinter
02-25-2008, 07:56 PM
Since this is a Kerdi shower, there's no chance of water damage if Paul uses grout and it cracks. If the corner studs are screwed together tightly before the wallboard is put up, it greatly reduces the amount of flex in the corner.

Grout will look better with the tumbled marble than some shiny silicone. I dont like the sanded caulks at all, they're usually only a siliconized latex which looks like crap in no time.


Edit:

My friend insists I push grout (SpectraLock !) into these before I caulk,

It would help if I read all of Paul's post the first time, eh? If caulk must be used, skip the grout... But I'm still saying forget the caulk altogether and just grout it! :tongue:

wizardpb
02-25-2008, 11:14 PM
Thanks to all - you guys and gals rock.

A short clarification: the backer on one wall (the long one) is directly on the studs, the other wall is sheeted with 3/8 ply, and backer dropped on that. I had to shim it to make the shower square, but it is sitting pretty firmly on the ply. I don't remember how the corners go together - I think they're pretty tight. I can check - the other side of the wall is not sheet-rocked yet. I might even be able to get screws into it from that side.

I guess grout might work. My only concern here is the ceiling. It's an old house that is being remodeled. The shower is downstairs, and the ceiling was moving drastically just with the foot traffic above it. We had to put steel plates on the (old) joists (which had already been reinforced with 2x12's) to stabilize it enough so that the ceiling tile would stay put. I think it could easily move some more. Especially since there's a Jacuzzi tub in the upstairs bathroom - directly over the shower.

And no problems about coloured caulk - the grout is bright white. The caulk will be bright white GE Silicone II. I hate those sanded 'siliconzied acrylic' caulks also. 'Siliconized latex' - what the hell is that ?!??!?

So I have two for caulk and one for grout. Anyone else want to chime in ? :-)

Thanks again!