# Adding glass block to existing shower wall



## tns1 (Jun 26, 2009)

I'll be adding a small glass block window to the upper 2ft of one shower wall directly above the shower head. This is an existing interior wall with a thickness of 5.5". The glass block is only 4" thick. Once I frame the window I was going to center the blocks over the framing, which would leave a 3/4" lip at the window edge. What is the best way to insure this lip does not cause moisture problems in the shower?


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## Blondesense (Sep 23, 2008)

Not an expert here, but in your shoes I think I would add a slope to that 3/4" so any stray splashes run off, then prime and paint with good quality latex. 

Since it is above the shower head and not susceptible to direct water hitting it you might be OK. Installing and using a good bathroom fan so the shower dries out properly will help. Still, wood in a shower is not a good idea, you might reconsider your plan.
I understand why glass block windows are used in a shower, but why are you installing it on an _interior_ wall? 
Just curious.


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## tns1 (Jun 26, 2009)

The interior wall is a few feet from an exterior wall with a window. 

The wall is normal framing but has cement board and plaster an inch thick on each side. There wouldn't be any extra wood or exposed wood. I was thinking of adding a vinyl sill or cap that would extend to the edge of the cement board but would be covered with thinset + tile. I had planned to slope the sill edge. 

The window above the shower head does not worry me as much. Now I've been asked to add a single glass block below and to the side of the shower head. I have not see a single post that says anything positive about windows in showers. The only possibility I see is if I found a vinyl window frame the full thickness of the wall.


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## Blondesense (Sep 23, 2008)

I'm dealing with a window in a shower right now, and believe me, I would get rid of it if it was an option.

You are right about one thing, windows in showers = bad idea. Putting holes in your shower wall when you don't have to is a bad idea. Windows are a significant weak spot when it comes to waterproofing a shower and you are looking at a strong possibility of leaks, mold, and water damage down the road. If you are trying to get more light, just install a light fixture. 



tns1 said:


> Now I've been asked to add a single glass block below and to the side of the shower head.


IMHO, Just say NO.


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## Ron6519 (Mar 28, 2007)

I would install the glass block flush with the tile wall. No recess, no issue.
Ron


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## tns1 (Jun 26, 2009)

I thought of that. The shower would look good, but the weight would not be centered over the framing, and I don't like the 1.5" sill on the other side. 

I have even considered leaving it as an open frame with no glass. The shower door is only 6ft high anyway so its not like this is an enclosed space. There is some framing on the ceiling that would act as a drip edge. The same flashing issues for an open sill still apply though. 

I think if I could find some vinyl window framing or u-channel to use as a cap, I could create a sill, glass or not, that had very low chance of leaking. If there are no holes in the sill material and it has a lip that extends over the cement board, then the only ingress points are the outer joints/seams. A full vinyl frame that fits the opening would be the easiest, best bet. In a pinch I guess you could make a custom sill cap/frame with a fiberglass repair kit.


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## tns1 (Jun 26, 2009)

I decided to leave the upper wall as an open frame with no glass block. The sill will be tiled with a slight drain slope. Extending above the sill is an open 2x4 frame which I have wrapped in plastic and sheathed in hardibacker just like the shower area. All screws had a dab of caulk on the threads. I have added metal edging to the outer edges of this wall. 

Should I also add metal edging to the open frame itself? 

I think it would not be necessary or desirable where the sill edge is going to be completely covered in tile - it might even cause problems.


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## GB Greg (Oct 14, 2010)

tns1 said:


> I'll be adding a small glass block window to the upper 2ft of one shower wall directly above the shower head. This is an existing interior wall with a thickness of 5.5". The glass block is only 4" thick. Once I frame the window I was going to center the blocks over the framing, which would leave a 3/4" lip at the window edge. What is the best way to insure this lip does not cause moisture problems in the shower?


I know you've already decided to leave the opening but to answer your initial question...

Since this is in a shower: I would use silicone to assemble the blocks. This way the window itself is water tight. Use marble for the sill, sides and head of the opening. If your finished wall thickness is 5.5", buy a 6" wide sill and hang it over .25" on either side of the wall. This way you can caulk the outside of the marble to the tile surface. Plan everything so that you have 1/8" clearance around the perimeter of your glass block section and silicone that to the marble. Your end product will be glass, silicone and marble. These parts shouldn't have any issues w/ water.

You should be able to find pre-finished marble sills at your local tile store. Most places who offer marble and granite counter tops would be able to cut these to your dimensions. The stock sills themselves are pretty inexpensive.


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