Glass Blocks Are Cracking

 
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Old 12-17-2010, 01:15 PM   #1
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Glass Blocks Are Cracking


I have a project with glass blocks that area cracking. These are original to the home. We removed two of the frames, which each have 2 vertical rows of six. They were removed a bit over a year ago as part of a dryrot repair project. One glass block was broken. We replaced it, removed all the dryrot, reinstalled the glass block, repaired all the stucco, retiled the inside of the shower where they are located, and completed the project in good standing. Recently, a few of the blocks are cracking. One on one of the frames, and two on the other. They seem to have all cracked on the inside of the glass, not the interior of the home side, but the interior of the block. The owner seems to have spoke with someone who thinks it has something to do with the framing, which is not at all clear, but for now I'll give it the benefit of the doubt. The blocks are simply installed within a 1x6 frame, set into the opening, then stucco moulding applied to the exterior, and tile butted up to the glass block frame from the interior. I can only suspect that perhaps there is pressure from the sides from movement causing them to crack (not enough expansion room). Strange thing is, there is the exact same configuration at the other end of this bathroom and the glass blocks have been there for years without cracking. I can't help but wonder if the shower location is lending to the problem. Any thoughts would help.

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To The T Construction, Inc.
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Old 12-17-2010, 01:26 PM   #2
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Re: Glass Blocks Are Cracking


I would suspect a structural issue above the opening.

Was the header over the opening replaced during your repair? Is there even a header there to begin with?

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Old 12-17-2010, 01:58 PM   #3
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Re: Glass Blocks Are Cracking


Quote:
Originally Posted by ToTheT1 View Post
I have a project with glass blocks that area cracking. These are original to the home. We removed two of the frames, which each have 2 vertical rows of six. They were removed a bit over a year ago as part of a dryrot repair project. One glass block was broken. We replaced it, removed all the dryrot, reinstalled the glass block, repaired all the stucco, retiled the inside of the shower where they are located, and completed the project in good standing. Recently, a few of the blocks are cracking. One on one of the frames, and two on the other. They seem to have all cracked on the inside of the glass, not the interior of the home side, but the interior of the block. The owner seems to have spoke with someone who thinks it has something to do with the framing, which is not at all clear, but for now I'll give it the benefit of the doubt. The blocks are simply installed within a 1x6 frame, set into the opening, then stucco moulding applied to the exterior, and tile butted up to the glass block frame from the interior. I can only suspect that perhaps there is pressure from the sides from movement causing them to crack (not enough expansion room). Strange thing is, there is the exact same configuration at the other end of this bathroom and the glass blocks have been there for years without cracking. I can't help but wonder if the shower location is lending to the problem. Any thoughts would help.

Thanks,
Craig,
To The T Construction, Inc.
Also the sill issue. Glass blocks require more support than a window because of the weight, double up the framing below,
allow 1/2" on a sides and top for expansion, use foam pipe wrap or fiberglass insulation in the spaces. Set on cushion.
Glass block panels should also have steel reinforcement in the joints that attach's to the framing,
and waterproof mortar.


The type of crack you're describing sounds like it took a hit from the outside.
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Old 12-17-2010, 04:39 PM   #4
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Re: Glass Blocks Are Cracking


There was definitely plenty of header and sill support. Also, each window opening was only two blocks wide and six blocks high. They're actually 8x8 blocks, not 6x6 as mentioned before. I don't think that bearing weight will end up being the problem.

I'm wavering now between it being my employees having too tight of an opening or water had entered into the mortar joints and reached the metal eventually expanding them due to rust and cracked the glass.

Likely I won't be able to get to the bottom of it until we decide to start tearing them out again. Biggest problem in the glass blocks were made in West Germany years ago and are no longer available. Of course there's a number of other windows in the same bathroom and also on the first floor that match.
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Old 12-17-2010, 05:09 PM   #5
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Re: Glass Blocks Are Cracking


Quote:
Originally Posted by ToTheT1 View Post
There was definitely plenty of header and sill support. Also, each window opening was only two blocks wide and six blocks high. They're actually 8x8 blocks, not 6x6 as mentioned before. I don't think that bearing weight will end up being the problem.

I'm wavering now between it being my employees having too tight of an opening or water had entered into the mortar joints and reached the metal eventually expanding them due to rust and cracked the glass.

Likely I won't be able to get to the bottom of it until we decide to start tearing them out again. Biggest problem in the glass blocks were made in West Germany years ago and are no longer available. Of course there's a number of other windows in the same bathroom and also on the first floor that match.
ll.
Check the expansion joints. Wood structures and houses breathe, glass block does not.
A house will expand and contract with the seasons.
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Old 12-17-2010, 05:40 PM   #6
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Re: Glass Blocks Are Cracking


Thermal stress ? Does that area get hit with alot of direct sun? at a weird angle where it is part shade on and part sun

Same as expansion and contraction but slightly more to it.

(Thermal stress) if part is hot and the other part cold glass will crack because it is not moving at the same rate within itself .. Or....umm.. what was the problem again?

These were removed and reinstalled, Maybe the removal was too much for them, Chipping mortar from brick breaks brick now and then.

One was already broken. how?

Back in the auto glass period of my life Customers would come back flipping a piece of moulding with their finger making it rattle saying "It never did this before" "Really" I would say. "Did you ever do that to it before" Usually they hadn't. But they just needed to check to see if i had done a good Job

Maybe they already had small cracks in them and the reno just got everyone lookin closer

Last edited by ccappaul; 12-17-2010 at 06:21 PM.
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Old 12-17-2010, 06:01 PM   #7
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Re: Glass Blocks Are Cracking


According to your original post I personally don't think it is structural... reason being if the block are 8x8 (taken from your other post) and there are 2 verticle columns then you are still roughly within a 16 O.C. normal exterior wall... no need for a header as your load is already supported due to normal framing practices. You basically have a punched opening, I would make sure you have a minimum of 1/4" and ideally 1/2", as essrmo stated, around the entire casement of blocks for your expansion and that should rectify your issue.
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Old 12-17-2010, 06:16 PM   #8
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Re: Glass Blocks Are Cracking


Thanks for the input all!

This won't be an easy fix, but i'm not going to let it ruin our company's reputation either. Plan to man up and do the right thing.

Happy Holidays to all!
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Old 12-17-2010, 06:22 PM   #9
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Re: Glass Blocks Are Cracking


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Originally Posted by SuperGlazier View Post
According to your original post I personally don't think it is structural... reason being if the block are 8x8 (taken from your other post) and there are 2 verticle columns then you are still roughly within a 16 O.C. normal exterior wall... no need for a header as your load is already supported due to normal framing practices. You basically have a punched opening, I would make sure you have a minimum of 1/4" and ideally 1/2", as essrmo stated, around the entire casement of blocks for your expansion and that should rectify your issue.
2 blocks wide and 6 blocks high, 8"x8", plus 1/2" on each side, top and bottom would require a

rough opening 17" x 43"
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Old 12-17-2010, 07:22 PM   #10
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Re: Glass Blocks Are Cracking


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2 blocks wide and 6 blocks high, 8"x8", plus 1/2" on each side, top and bottom would require a


rough opening 17" x 43"
Wrong what about the grout joints? It would most likely be 17 1/2 X 45 1/2. At least that's how I frame them leave room for 1/2" Grout lines if the smaller its easier for the tile guy to fir in the opening a little than to have an opening to tight.
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Old 12-17-2010, 08:30 PM   #11
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Re: Glass Blocks Are Cracking


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Wrong what about the grout joints? It would most likely be 17 1/2 X 45 1/2. At least that's how I frame them leave room for 1/2" Grout lines if the smaller its easier for the tile guy to fir in the opening a little than to have an opening to tight.
Manufacturer accounts for grout joints. http://www.sizes.com/materls/glassBlock.htm
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Old 12-17-2010, 08:37 PM   #12
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Re: Glass Blocks Are Cracking


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Originally Posted by essrmo View Post
Manufacturer accounts for grout joints. http://www.sizes.com/materls/glassBlock.htm
oooooo.......you been had
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Old 12-17-2010, 09:14 PM   #13
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Re: Glass Blocks Are Cracking


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Manufacturer accounts for grout joints. http://www.sizes.com/materls/glassBlock.htm
Maybe some do but I know some do not. I learned the hard way on a curved wall with glass block (interior windows). Got to do quite a bit of fixing after drywall. Like i said its easier for them to fir in then make a hole bigger.

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Old 12-18-2010, 06:06 PM   #14
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Re: Glass Blocks Are Cracking


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Originally Posted by skyhook View Post
2 blocks wide and 6 blocks high, 8"x8", plus 1/2" on each side, top and bottom would require a


rough opening 17" x 43"

I also said he is roughly within a standard 16 O.C. framed wall. That one inch is not going to crack the inside of a glass block like that there isn't enough load.
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Old 12-18-2010, 08:36 PM   #15
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Re: Glass Blocks Are Cracking


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I also said he is roughly within a standard 16 O.C. framed wall. That one inch is not going to crack the inside of a glass block like that there isn't enough load.
You can frame 24 in oc and not have problems either unless theres huge point loads on it.
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Old 12-18-2010, 08:46 PM   #16
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Re: Glass Blocks Are Cracking


We still don't know the (e) rough opening but it had to be framed too tight if the blocks are cracking.
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Old 12-18-2010, 10:47 PM   #17
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Re: Glass Blocks Are Cracking


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Originally Posted by skyhook View Post
We still don't know the (e) rough opening but it had to be framed too tight if the blocks are cracking.

Hence the rest of my post...

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