# Glass block in wood frame wall



## dielectricunion (Feb 27, 2013)

Apologies in advance, this is kind of an ignorant question... I've never worked with glass block before. I'm adding two simple "windows" in a newly built exterior wall. Is it practical to make your own mortar mix? I have lime, Portland, and sand. Obviously not white, but this is for my own place, not a customer, so I'm not sure that I mind grey. All I'm installing are two vertical lines of 6 blocks, 8x8s. Can I build a wood frame or is there a metal track that's more preferable?


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## Tscarborough (Feb 25, 2006)

Mortar to wood will always crack. Better to use a vinyl or metal channel frame and caulk the dis-similar materials.


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## dielectricunion (Feb 27, 2013)

Yeah I wasn't imagining that mortar wasn't going to fit in, but I definitely like the look of mortared block better than those pointed with a silicone or other tube product. Should be pretty easy to frame it out using the PVC track. Just wanted to make sure I'm not buying some DIY track accessories that were totally unnecessary.


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## Tscarborough (Feb 25, 2006)

If it is 1 block wide, 6 block high you do not need any accessories other than the channel, mortar, and caulk.


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## dielectricunion (Feb 27, 2013)

I've seen a few types of stainless rebar but I assume that's not needed in single block to block joints only 1 wide


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## Fouthgeneration (Jan 7, 2014)

If there is any chance the glass block will be bumped during their lifetimes, I'd band them with some galvanised wire.

Some block are availiable with a factory white coating that increases light transmittal when laid in non white mortars.

I'd follow Tscar advice and use the plastic channel and lay up the glass block and wrap with the channel mold in a jig an eight inch smaller then the opening, let it set up a couple of days then slide the whole block sash in your R.O. Installing the block in the channel mounted in the opening would be rather difficult.


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## mikeswoods (Oct 11, 2008)

Most brick yards will build and band the blocks for you---this way you do not need to learn the masons trade---very reasonable charge at my brickyard.


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## dielectricunion (Feb 27, 2013)

mikeswoods said:


> Most brick yards will build and band the blocks for you---this way you do not need to learn the masons trade---very reasonable charge at my brickyard.


 I've tried the masons trade here and there and it's safe to say I've got a lot more practice ahead of me!


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## stonecutter (May 13, 2010)

dielectricunion said:


> Yeah I wasn't imagining that mortar wasn't going to fit in, but I definitely like the look of mortared block better than those pointed with a silicone or other tube product. Should be pretty easy to frame it out using the PVC track. Just wanted to make sure I'm not buying some DIY track accessories that were totally unnecessary.


Just use a sanded caulk. That replicates mortar pretty well and you can color match it to your grout once it dries.


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## dielectricunion (Feb 27, 2013)

This is one of the glass block windows I'm attempting to frame. Not sure if this is going to be acceptable but im going to assemble it and see if it works. Most of my difficulties have been figuring out how I'm going to trim/flash and tie it into the aluminum siding that will be on the outside.

It's in my own house (like most of the unpaid projects I've been working on for the last year) otherwise, I would not be convincing a client that I knew what I was doing!


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## dielectricunion (Feb 27, 2013)

...


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## dielectricunion (Feb 27, 2013)

please criticize :wheelchair:


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## dom-mas (Nov 26, 2011)

looks ok


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## CarpenterSFO (Dec 12, 2012)

I put 2 drip caps over the top row of block - once inside the frame, and once over the top of that, and flash the inside of the frame all around with metal - copper usually - sometimes with a small lip inside, but usually with the flashing stopping just short of the interior side of the block. Glass block will eventually fail - you have mortar joints from exterior all the way to interior, and you need to be ready for water to get at least half-way in, and if it runs to the sill, to have a way out.

I like glass block a lot, and have done a few projects, maybe a dozen, with it. I spend much more time flashing than setting the block itself. I wish more people liked it, as I like the look.


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## Fouthgeneration (Jan 7, 2014)

Maybe a Aluminum/wood/plastic 'wood'- framed "storm" pane to provide another layer of protection.....removable for cleaning, and raises 'R' value.


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## dielectricunion (Feb 27, 2013)

Fouthgeneration said:


> Maybe a Aluminum/wood/plastic 'wood'- framed "storm" pane to provide another layer of protection.....removable for cleaning, and raises 'R' value.


Not a bad idea. I would need an odd size. What is the R value of standard glass block anyway? I made plywood spacers between the blocks and will be using sanded caulk or silicone to seal the joints. Do full mortar joints have better insulating value than silicone/caulk? I'd imagine so, except having an air gap between should add to that.



CarpenterSFO said:


> I put 2 drip caps over the top row of block - once inside the frame, and once over the top of that, and flash the inside of the frame all around with metal - copper usually - sometimes with a small lip inside, but usually with the flashing stopping just short of the interior side of the block. Glass block will eventually fail - you have mortar joints from exterior all the way to interior, and you need to be ready for water to get at least half-way in, and if it runs to the sill, to have a way out. I like glass block a lot, and have done a few projects, maybe a dozen, with it. I spend much more time flashing than setting the block itself. I wish more people liked it, as I like the look.


What do you mean 2 drip caps? I plan to install an aluminum drop cap but not sure how an additional one would be integrated.


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## Railman (Jan 19, 2008)

I'd use silicone for the joints. It's flexible, has good adhesion to the glass, Will insulate better than mortar, is near invisible, & is a lot less likely to leak, especially in a wood frame. From what my supplier told me when I did some in my shop, they do mostly silicone these days.


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## Fouthgeneration (Jan 7, 2014)

As a 'diaper' to SFO drip caps, I'd tin or flash the bottom of the R.O. with 'sticky back' EDPM flashing to route any leakage out to the face of the siding below the window--Just as any properly installed window/door would have.........the window pan draining into a 'drip edge' under it at the sill.

There has couple of good threads regarding rain screen walls and flashing around penetrations, I use a sky light or chimney as a model for routing the water back to the surface/exterior of the roof/wall system.

Local land grant University has a glass block 4 story stair well that they have to sump pump the basement landing during heavy rains from the East. It IS AN ENGINEERING building, but not the Con E. one.......


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## CarpenterSFO (Dec 12, 2012)

dielectricunion said:


> Not a bad idea. I would need an odd size. What is the R value of standard glass block anyway? I made plywood spacers between the blocks and will be using sanded caulk or silicone to seal the joints. Do full mortar joints have better insulating value than silicone/caulk? I'd imagine so, except having an air gap between should add to that.
> 
> 
> 
> What do you mean 2 drip caps? I plan to install an aluminum drop cap but not sure how an additional one would be integrated.


Really a flashing with drip edge inside the rough opening, and a flashing with drip edge above, lapped over the one inside. If you're installing that frame as a piece, the one above can be a full drip cap. You REALLY want to keep water away from that top edge.


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## dielectricunion (Feb 27, 2013)

I've read a bunch of building science articles and other miscellaneous stuff on flashing and rain screens, vapor barriers.

I feel stupid that I still can't seem to totally wrap my head around the right way to build, install & flash in a particular situation. I've only done bits and pieces of siding and window / door installation.

I still don't completely understand the mechanics of a window pan, sloped sill and weep holes. The sill on this glass block assembly is just a solid 2x chunk with a drip grooved cut and beveled slope. I know this isn't ideal but since it's on my own house, I can see how it fares with age and learn my lesson.


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