How to Install a Glass Block Window

By Gene and Katie Hamilton

Tools Required
  • Tape measure
  • Hammer
  • Pry bar
  • Chisel
  • Drill/driver
  • Level
Materials Required
  • Glass block window
  • Silicone caulk
  • Caulking gun
  • Insulation (fiberglass or
    low-expansion aerosol foam)
  • New interior molding
  • New exterior window trim

Before You Begin

Take steps to protect interior surfaces from tools and materials as you work. If the window is located over the tub, put down a few layers of cardboard and cover it with a thick blanket or folded drop cloth.

For this installation, we'll presume you want to replace the old window with a new one of approximately the same size. Don't start removing the old window until you have your glass block window on hand (especially if it is a special order). But before you place your order, remove the interior trim surrounding the existing window and measure the rough opening. You want to be sure that you won't have to make changes to the wall framing unless it's absolutely necessary. If you can't get a glass block window to fit this opening, you may have to order a smaller size rather than enlarge the framing. Keep in mind that rough openings are about an inch or so larger than the actual window, which gives you room to shim and level the window in place.

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  • Step 1 : Prepare the opening

    With the interior window molding removed, look in the gap between the jambs and wall framing and find the nails or screws that hold the window in place. Many older windows are nailed through the sides of the jambs into the framing, usually through shims (thin wood shingles, or any material used as spacers to position the window in the opening). You may not see the nails because they were driven through the shims. Split and remove the shims with a chisel, then use a metal-cutting blade to cut through the nails or screws.

    (Note: Modern windows are often fastened through an integral flange attached to the exterior edge of the jambs. It may be necessary to remove this type of window by pulling the nails from the outside.)

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