How to Make Glass-Block Windows

Updated July 01, 2018

Glass block is beautiful, durable and secure. Most homeowners and builders use it in locations where light is needed but ventilation is not required. Glass-block windows are commonly found in garages, basements and bathrooms. Glass block is a great replacement window or a good choice for new windows in these and other areas of your home. You can install a glass-block window yourself. Basic carpentry skills will suffice for this project.

Remove inside trim around the window and measure the window opening carefully. Subtract 2 inches from each width and height measurement to allow for insulation and the glass-block window’s framing track.

Count the number of courses from top to bottom of the opening and the rows from side to side. Use these measurements to calculate the total number of blocks needed.

Repeat measurements and check for accuracy. Sketch the completed window, per your calculations.

Order the glass blocks for your window as a ready-made unit for the quickest installation option. The dealer or distributor will assemble your window, apply the silicone sealer or mortar, and band all the blocks together.

Buy rectangular or square blocks in the sizes required for your window opening from a distributor or home improvement centre if you prefer to assemble your window. Select one size or a combination of squares and rectangles required to fill the opening. Blocks cannot be cut.

Remove the existing window, if this is a replacement installation. Remove any loose debris from old window.

Measure and cut the block track or channel to fit the window opening. Attach the channel to all four sides of the window jamb with screws.

Set the individual blocks or the assembled glass block panel into the opening and level them.

Insert spacers between each block on each row. Insert a reinforcing strip on top of each course before adding the next row of blocks. If you ordered a panel, skip this step.

Apply silicone sealer horizontally and vertically between individual glass blocks. Wipe away any excess sealer as you go along.

Apply caulk between the blocks and the track to seal the window. Insert furring strips or foam expansion strips, if necessary to get an exact fit between the glass blocks and the tracking.

Wait for caulk to dry and apply trim to your new glass-block window.


Consider different types and sizes of glass blocks. Clear blocks let in light and increase view from outside and inside. Textured blocks let in light, without providing transparency.

Glass-block windows can be ordered as panels for ease of installation. Experts recommend this option for homeowners.


Assembled glass block panels are heavy. Get help when lifting your panel into the window opening.

Things You'll Need

  • Glass Blocks
  • Channel
  • Silicone Sealer
  • Caulk
  • Spacers
  • Drill
  • Putty Knife
  • Screws
  • Tape Measure
  • Marker or Pen
  • Level
  • Reinforcing strips
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About the Author

Carol Luther has more than 25 years of business, technology, and freelance writing experience. She has held leadership roles in higher education management, international development, adult education, vocational education, and small business support programs