How to Install a Glass Block Window into a Wood Frame in 8 Simple Steps


How to Install a Glass Block Window into a Wood Frame in 8 Simple Steps

More than ever contractors and do-it-yourselfers are electing to install glass block windows due to the numerous benefits glass block windows offer like security, privacy and energy efficiency.

Most contractors know that mortar does not adhere to wood properly. The wood sucks the moisture from the mortar and begins to flake off and even shrink; leaving the window unstable, leaky and even drafty. Here is an easy to follow 8 step process to install new glass block windows into a wood frame opening.

What you will need to get started

  • Carpenter Bar
  • Glass Block Silicone
  • Shims
  • Level
  • Glass Block Window
  • Tuck-pointer (or flathead screwdriver)
  • Insulation (Roll or spray minimally expanding)
  • Aluminum Capping (optional)
  • Parting Stop (cut final size, saw may be needed)
  • 1 ¼ inch staples with high powered staple gun  (or finishing nails with hammer)

1.       Removing the Sash

In most cases the existing frame can stay. Simply remove the sash and remove any hardware that will get in the way of the new glass block window. You may need to use a chisel in some places to tear away some of the frame that keep the new glass block window from fitting in properly (if it is a vinyl framed window, remove the entire frame).

2.       Set the shims

Set as many shims as needed on the left and right sides on the bottom of the opening to secure the glass block window in place. Try to estimate the placement of the shims so that when the new window is placed, the glass block joints are not directly on top of the shims (Try to avoid having unnecessary stress on the joints of a glass block window).

3.       Setting the Window in Place

Before attempting to set the window, be sure to have a carpenter bar, another handful of shims close by or in a back pocket and a level. Learn from others past mistakes and never turn a shoulder to a window that is not securely in place, this will save money and potential hospital bills. Set the glass block window centered into the opening using the carpenter bar to gently adjust the window to center and level it. Put enough shims into the top center and tap securely into place to keep hold the entire window in place while getting ready for the next step.

4.       Cut the Shims

Using a razor knife, cut the excess from the shims directly even with the face of the glass block for an easy installation of parting stop and exterior wrapping and framing.

5.       Fill with Insulation

The last thing a property owner wants is leakage through a window, so pack the edges with as much insulation as possible (or use the minimally expanding spray-in insulation. Using a tuck-pointer (or screw-driver) for this makes it really easy. Just tear small pieces off of the roll and turn the tuck-pointer sideways to fill the tiny gaps between the frame and glass block window.

6.       Install the Parting Stop

The parting stop can be of preference, we generally use ½ x ¾ inch parting stop made of pine. The size and type is completely optional that should fit the project requirements. The parting stop should go completely around the interior of the window and extend in front of the glass block window by at least ¼ of an inch. Hold the staple gun as close to the glass block window as possible and secure the parting stop to the frame.

7.       Silicone

The silicone will give an airtight and watertight seal to the glass block window. It can get messy, but using soapy water to spread thin lines will help to remove excess silicone, just use a lot of soap and remove excess silicone immediately. Use the clear silicone against the glass block window and parting stops. Cover all the tiny gaps. The recommended silicone is approved for use with glass block window, the glass block silicone can be purchased here. Use whatever color silicone needed for other areas as needed.

8.       Framing the Exterior

Now all that is left is to frame the exterior of the new glass block window. Do so according to the project requirements or property owner’s preference.


Now not every project is as cut and dry as this. Every window opening is different and ingenuity with resourcefulness will come in handy just like most window installations. Should a property owner, contractor or construction professional ever run into issues while installing glass block windows or other glass block structures, the professionals at Quality Glass Block and window Co. are just a call away to lend support and offer expert advice and guidance.