How to Install Glass Block Spacers

Written by barbara freeman
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How to Install Glass Block Spacers
Glass block wall. (glass block image by Sunshine Photos from

The messy mortar used to build breeze block walls is no longer necessary for constructing glass block windows. Instead, you can use horizontal and vertical spacers and bond them with a silicone sealer. The spacers are an innovative way to consistently and evenly assemble glass blocks You can purchase the spacers in pre-cut systems that include everything needed to build a professional-looking window.

Skill level:

Things you need

  • Measuring tape
  • Drill
  • Wood screws
  • Glass blocks
  • Silicone sealer
  • Vertical spacers
  • Level tool
  • Anchors
  • Horizontal spacers

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    Installing spacers to construct a glass block window.

  1. 1

    Measure the length of the area you will use to build the glass block wall, then divide this by the width of one glass block. This will give you approximately the number of glass blocks you will need for one row.

    How to Install Glass Block Spacers
    Measure the area and divide by the width. (measuring tape image by Rich Johnson from
  2. 2

    Install channel sections end to end around the glass block frame, using a drill and wood screws. The channels will serve as a brace to hold the glass blocks in place.

    How to Install Glass Block Spacers
    Install channels using drill and wood screws. (drill image by Vladislav Gajic from
  3. 3

    Test the first row of materials for correct fit. Start at the right corner of the first row by fitting one glass block securely into corner then adding one spacer. Continue the pattern of adding blocks and spacers all the way to the end of the first row. When you feel they are correctly aligned remove the blocks and spacers.

  4. 4

    Apply two rows of silicone lengthwise onto bottom window channel. Then, starting at the corner of the window, place the first glass block securely into the corner and the bottom channel of the frame. Add four dots of silicone onto the side of the first glass block and press on the first vertical spacer. Continue this pattern to the end of the first row using the level tool to make sure each glass block has been installed correctly.

    How to Install Glass Block Spacers
    Use level to install each glass block. (level image by Albert Lozano from
  5. 5

    Place an anchor securely into each side of a horizontal spacer to keep each row of glass blocks stable. Apply two dots of silicone to the top of each glass block in the row and carefully press the horizontal spacer into place (with the anchors facing up). Because channels have been installed, attach the anchors with silicone glue, not screws.

  6. 6

    Repeat the pattern for each row using glass blocks, vertical and horizontal spacers and silicone bonding. Add two dots of silicone to the top of each block in the last row. Do not use a horizontal spacer for this row. Fit each glass block and spacer into top window channel by repeating the glass block, spacer and silicone pattern until you reach the last spacer and block.

  7. 7

    Fit the last glass block into the corner of the window, then fit the spacer in place.

    How to Install Glass Block Spacers
    Glass blocks and spacers make a beautiful window. (woman and glass blocks image by cullenphotos from

Tips and warnings

  • If you do not use channels for this project, use wood screws instead of silicone. This will help stabilise the glass blocks.
  • Make sure the frame is strong enough to hold the glass blocks.

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