Lots of Cracked Glass Block Windows

[Mike Lamb]

An all brick house I looked at recently had glass block windows at the basement. There were seven windows and each had 3 or 4 cracked glass blocks. Structure and lintels were fine so no pressure of that kind.

I?m sure thermal expansion of the glass caused this but am interested in any more info or experience you may have. I see so many glass blocks that are doing just fine. I?m think it?s just bad glass. Right?

[Mike Lamb]

I see if I type in Word and paste, the apostrophe's come out as question marks.

[kurt]

Contrary to popular opinions, glass block is not structural. So, anything is possible, but I'm guessing stress from somewhere.

They could have jacked it up by fitting the lintels too tight; if there's no expansion capability, that'll crack them.

The slightest lintel delam will crack them.

[Tom Raymond]

Were they original or retrofit?

Glass block retros are an incredibly low margin product so they tend to get slapped in. Around here it's very common to wedge a unit in with shims on all four sides, squirt in some mud with a bag and strike it off flush with the opening, a 15-20 minute job including demo and clean up. The good news is that they're cheap, common sizes tend to be under $200 installed.

[Mike Lamb]

Not original windows. They never are around here. Thanks all.

[mgbinspect]

One would think that if it was stress from differential movement, the glass would more likely shatter, than simply crack. I lean toward Mike's assessment - thermal expansion - quick change in temperature maybe?