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Question:

What gap do I need when building my glass Block windows?

I'm putting glass Block windows in my barn. A lot of them. I need to build all the openings first. When figuring out my openings I need to allow for the gaps between the blocks and around the edge. What should that gap be?

Answer:

Glass masonry units are typically square, and are available in nominal 6, 8, and 12 in. sizes. Rectangular units are also available. Actual sizes are 1/4 in. less to allow for the typical 1/4 in. mortar joints. Unit thicknesses are either "standard" 3-7/8 in. or "thin" 3-1/8 in. or 3 in. for hollow units and for solid units respectively. Thin unit panels are typically used in residential and light commercial applications. For exterior applications you will want to add integral water repellents to the mortar to prevent water penetration. If you are talking about what size of an opening to use for your windows. That will depend on what the "rough opening" dimension is based on the window manufacturer. Typically is is 1 in. larger than the window size. This gives you 1/2 in. space all around the window for shims and alignment.
Apr 14, 2017

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