How to Install Thickset Glass Blocks in an Exterior Wall

Written by kimberly johnson | 13/05/2017

Glass blocks are decorative building materials that can add a unique appearance to interior and exterior decor. Although most often used in office buildings, they are also very popular building materials for bathrooms.The glass blocks allow light to filter into rooms while providing an opaque appearance for privacy. Glass blocks are installed in a similar manner to standard bricks, but care must be taken to clean up all of the silicone around the edges.

Measure the width and length of the exterior opening with a tape measure.

Calculate how many glass blocks are needed by dividing the width of the opening by the size of one glass block. Then divide the length of the opening by the size of one glass block. Add the numbers together to determine how many total blocks are needed.

Frame out the opening with flat pieces of wood that are the same width and length as the opening. Attach the wood to the wall by applying wood glue to the bottom of each piece and then placing it into the opening. Insert long screws into the surrounding wood joists to secure it.

Place the glass blocks into the opening to make sure they fit. Then remove them to begin installation.

Cut the glass block mounting channels to fit each side of the exterior opening. Use a tape measure and hacksaw.

Attach the mounting channels to each side of the opening, using screws and a screwdriver.

Apply a thin layer of silicone sealant down the centre of the perimeter of a glass block. Place the block flush against one side of the wall opening. Gently hit the top of the block with a rubber mallet to spread the sealant out.

Insert a plastic spacer next to the glass block. Then apply silicone sealant to another block and place it next to the spacer. Tap it with a rubber mallet.

Install blocks and spacers until the entire opening is filled with blocks. Allow the silicone sealant to dry for 24 hours

Remove the spacers from between the glass blocks.

Apply a thick layer of silicone sealant into the openings between each block. Allow the blocks and sealant to dry for an additional 24 hours before exposing them to humidity such as a shower.


Wipe off all extra sealant from the glass blocks.

Tips and warnings

  • Wipe off all extra sealant from the glass blocks.

Things you need

  • Glass blocks
  • Wood
  • Wood glue
  • Glass block mounting channels
  • Hacksaw
  • Screws
  • Plastic spacers
  • Clear silicone sealant
  • Rubber mallet
  • Rag

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