Stories From the Field

Post: Glass Block Windows

Wednesday June 12, 2019

AAA-1 licensed masons installing a wavy-styled glass block window unit in a basement opening

Traditional windows with an operable sash are made by companies like Marvin, Pella and Kolbe, and are commonly installed by a carpenter or window contractor. But because glass block windows require the use of mortar, their installation is best left to licensed masons.

Glass block windows are comprised of individual glass blocks and these come in a multitude of patterns (e.g., wavy glass, opaque glass, diamond-etched glass, etc.) and sizes (e.g., 12” X 12” panes, 8” X 8” panes, 4 X 6” panes, etc.)

In this photo, the masons are installing a wavy-styled glass block window unit in a basement opening. The individual glass blocks measure 8” X 8” and provide a modicum of privacy.

Because glass blocks have thick interior and exterior glass walls, glass block windows are very strong and provide an extra level of security not found in traditional windows (from time to time we find small caliber bullets trapped between the panes of glass).

Glass block windows can be constructed pane by pane in the field using mortar but this does not produce a very weather-tight product because mortar does not bond well to glass. To ensure the highest quality glass block windows, we construct our windows differently: First we lay out the glass blocks on a flat table in the configuration required. Then Portland cement is added between the individual glass blocks, the entire unit gets banded together with steel strapping, and then baked in a temperature controlled kiln which allows the Portland cement to fuse to the glass blocks.(We only use mortar around the perimeter of the glass block window during field installation where the blocks make contact with the brick jambs and windowsill.)

AAA-1 Masonry & Tuckpointing has been installing glass block windows for almost as long as there have been glass block windows!For a free estimate for your next glass block window project, please give us a ring at 773/622-7300 or via e-mail at

Thank you,


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