Bath Reno - Glass Block-to-wall tile seal, trim questions [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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07-24-2019, 12:35 PM
Hello, and Help!
I'm working on renovating my 1st floor bath w/walk-in shower in my 1920's "Old Style" brick home.

I recently had a glass block window installed (will be in the walk-in shower), and have insulation scheduled to be sprayed in the outside wall and ceiling in a couple of days.

I'm finally getting around to building up and replacing studs and framing on all the open walls, in preparation for drywall and underlayment for the tile walls and walk-in shower, and I'm struggling with the area immediately surrounding the glass block!

(The first photo shows the whole window, and me test-fitting new framing along the left side. I've since proceeded with actually installing some framing along the right side.)

The installers left the interior window frame quite rough and uneven, so I'm attempting to add in framing around the glass block, but because of how rough the framing is, i'm not sure how to proceed (I've tried to capture the "cavity" around the window, and my current approach to "framing in" new wood - everything lighter colored - in the attached photos.)

My questions:
1. Should my goal be to bring in the new framing right up to the edge of the glass block - or should i be leaving a narrow gap to be filled in later with a tile-trim piece? The windows sits back a bit from the interior studs, btw.

2. Do i need to be concerned about condensation or sealing the "inside" channel of my new framing - the surfaces that will face the edge of the glass block. There's a channel-space between my new framing and the GB that I can't close up with wood pieces due to the uneven-roughness of that old window frame the installers used to sit the GB inside of! Can I just fill it with insulation? Leave it? Prime/paint/protect the inside?

CURRENTLY: I've already installed a new "stud" along the right side, with that small square-profile length of pine trim attached in an effort bring this edge in closer to the GB - and there's room to attach another, which would almost exactly abutt the GB (image of the lower right corner, and then the close-up looking down the "channel" show the already installed piece).

But now i've paused because i'm not 100% sure this is the best approach -



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08-01-2019, 02:09 PM
...? any opinions or suggestions?

08-01-2019, 04:46 PM
Jose, you've got a puzzle there for sure. I'll answer as if I were doing for myself. I'm confused how they actually mounted window. Was it an assembly or build in place? What does it bear on? Glass block or acylic?

1. I'd run tile and waterproofing to butt into block with a bead of silicone caulk in small gap left between the two. It looks to me like you'd need to fur the wall into the room some to create more of a recess and a game plan. My mind's eye would like something close to 3/4" or 1". If I had the space in the room, I might fur it out further and make that window into a cool looking niche.

2. If you use a surface applied membrane you'll save yourself a lot of grief. Also foam boards are great for stuff like this. Framing and window have to be solid and if waterproofed correctly moisture migration shouldn't be an issue into house frame at all.

08-01-2019, 05:02 PM
Sorry you got missed there, José, but I was about to respond saying that it's likely nobody wanted to take that on because the only practical time to decide how to finish the inside would have been before you installed that window.

And like Peter, I'm wondering just how that window was installed and properly weatherproofed on the exterior. I see no evidence in your photo of any sort of flashing at all in the opening. Also, not having a geographic location in your User Profile doesn't help in knowing just how much of a problem you might have in that regard.

I tend to agree with Peter that doing some more framing to allow your to have a more appropriate material adjoining the glass block might be the best approach, but I can't really tell what difference you currently have between the plane of the glass block and the plane of your wall framing.

My opinion;n worth price charged.

08-01-2019, 09:33 PM
Carbidetooth: thanks for your ideas - they're helpful. The GB window is actual glass, was pre-assembled, and was mounted within the old wood-framed rough opening that encased the original window (which was original to the house, from my assessment). This is the rough, uneven, splintered frame that is causing at least some of the problems. I didn't realize the condition of it before demo - and I didn't think the installers would just plop the new GB right on it if it were an issue.

This old wood frame would be the equivalent of the "prefinished window frame" in the image below.

If I continue with my current approach, I'd end up with a "recess" of about 5/8" - do you think that'd be enough to work with?

I'm planning on using Schluter-Kerdi membrane - how would the foam board work/help in this situation?

cx: thanks to you as well! I'll fix my profile-location info, but I'm in southeastern Wisconsin. The installers arrived at the site, removed my old window, and inserted the glass block. This after a preliminary visit to assess the job and provide me an estimate for installation. In terms of weather-proofing, it looks like it amounted to sealing the seam between GB and old window frame, inside and out, with caulk.

The GB sits back from the wall-stud framing about 5/8". I could frame right up to the edge of the GB if need be. Do you think 5/8" is enough to work with, or do I need to consider furring the wall out into the room further? It's not a big bathroom, so I can use every inch i can get!

Bottom line, i guess: Do I need to worry about how to seal the wood in the frame to keep moisture from rotting the frame or getting in the wall?

08-02-2019, 01:44 AM
As I see it you have two concerns here. Judging by the construction, I'm betting old house. Perhaps '50s or earlier.

First, indulge me by tapping the glass block with a key or coin. Glass will "tink", acrylic will "thud".

Installing replacement windows in old sash work is common practice. I don't think much of it, but it solves problems for installers when it comes to preserving existing exterior trim and siding. What is doesn't do very well is attach the new window to the FRAME of the house. In your case it seems it mostly attaches it to the sheathing (boards).

With access from the inside best install would have framed that opening to appropriate size and installed the new window through sheathing into frame. Flexible flashing would be applied and hopefully tied to building (tar) paper for weather resistance. Exterior then trimmed to match. There are variations of the theme, but suffice to say if wasn't done well and the window is exposed to weather, there is every possibility it will introduce water into wall. Never good.

For the window to be included in the shower ASSEMBLY it must be tied to the house frame. Some would probably argue this, but it's the best chance for a trouble-free future. If it's in fact glass, the window assembly would likely weigh in at something over sixty lbs. A fair amount of weight tugging on movable parts.

Concerning finishing interior. 5/8" is workable if not ideal. Add to that typical 1/2" of tile backer and with foresight you can create a tile-able, waterproof surface. Attach that surface to the block with a redundant seal and you've got a shower that will last and last.

This is where foam boards come into play for me. Assuming I have a surface to attach too, I could line that surface with 3/16" Kerdiboard, seal it to block, then tile up to window and seal once again. Of course that necessitates the waterproof surface to wrap around to on shower wall itself. Hence the recommendation for surface membrane which makes this transition easier.

All I recommend gleaned from demo-ing many that didn't stand the test of time and caused significant collateral damage. More modern materials have made this a bunch simpler. If I look back and think of folding building paper Origami style into window openings it seems pretty janky to me now. Stuck in the mud in some ways, I suppose, but will certainly embrace newer techniques that stand up to (my) scrutiny.

That's my litany. Take what you will.

08-03-2019, 01:55 PM
I did the soundcheck, and it is indeed glass.

thanks again for sharing your expertise!