3 inch glass Block --- Window or Structural Support????

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Posted by: from Edmonton
5/20/2011 at 10:40:34 AM

Hi there,

I have a 6 and a half foot long 'window' in my basement that is made up of thick glass blocks. I was told that I wont be able to install another window along that same wall because there is a rule that only 25% of any one wall in a basement can have windows in it. I am wondering if these glass blocks will count as a window since they seem to be part of the structural support??

Thanks so much for any help!

3 inch glass block --- window or structural support????
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Dave in Oshawa
Date/Time5/20/2011 at 11:35:14 AM

You're going to have to talk to your local municipal building official. Codes and standards vary across the country. Some provinces have their own Building Codes and some use the model National Building Code. I'm not sure what the requirements are like in Alberta, but I do know that you guys have very strict fire regulations on limiting distance from one house to the next. Glass blocks may or may not count towards the allowable window area in a side wall. They are however, not structural. It's best to go to the source for advice on this. Don't be afraid of them, the Building Officials are (supposed to be) there to help.

~ Dave

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Date/Time5/20/2011 at 3:34:20 PM

Your glass block won't be structural and the more access to the outside the better. There is no maximum allowable space from the basement to the outside. The determining factor will be the distance the floor structure above can span its support. You should always check with your local authority. They will tell you what they like to see. If you are pulling out glass block to put a window then you shouldn't have a problem.


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Date/Time5/26/2011 at 11:49:40 AM

Hi Jeremy,

I would also say that the glass blocks are definitely not structural in any way. If you were going to install a window there, why not just remove the glass blocks and install a window in its place? This would address the question of if you have too much window space on the wall , and it would give you your window that you want as well. I am not sure what the codes are for your province, so a call to the local inspections office would surely help answer more of your questions.

Hope that helps,

Bill Clawsie

Clawsie Contracting


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Norman in Ottawa
Date/Time8/10/2011 at 3:30:27 PM

As I understand, the building code says that a window size in a bedroom must be a minimum size. (usually 5% of the room's floor space) ie. If the room is 10x10=100 sq feet than the window's minimum wall size must be 5 sq feet. Therefore, a window size of 30" high x 24" wide would suffice.

3 inch glass Block --- Window or Structural Support????

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