How To Replace A Single Pane Of Glass In A Wood Frame With A Glass Block Pane

30 June 2016
 Categories: , Blog


If you want to add interest to a window, replace the glass with glass block window. Glass block window panes save energy, and they allow more light without sacrificing privacy. It can be done by a beginning DIY enthusiast. Here are some tips to replace a single window pane with a glass block.

Prepare to Work

For this project, you need:

  • work gloves
  • pencil
  • soft cloth
  • measuring tape
  • pliers
  • putty knife
  • flat-blade screwdriver
  • hair dryer
  • hammer
  • cardboard strips the size of the blocks or wood spacers
  • wood shims
  • cement-based glass block mortar
  • trowel
  • wood preservative
  • caulk and caulk gun
  • wood trim
  • glass block pane

Measure the height and width of the window opening excluding the frame, and add about one-fourth of an inch to allow for mortar. Take the measurements to a glass maker. Don't remove the old glass pane, since it may take several days for the glass block to be ready.

Remove the Old Glass

Determine how the glass is attached to the frame. If it has trim, work the tip of a flat-blade screwdriver between the window jamb to free it, and use the claw end of the hammer to remove nails. If the frame is attached by glaze, heat the glaze with a hair dryer on a high setting, then scrape the glaze with the putty knife.

Use pliers to pull out the spikes. Loosen the glass by tapping it with your hand from the outside. Slowly remove the glass from the frame, and get someone to hold the glass from the other side, if needed.

Install the Glass Block Pane

Set the glass block pane in the window for a test fit. Place wood shims across the bottom of the frame, and insert cardboard pieces or wood spacers tightly in between the shims to act as mortar joints. Mark on the frame to indicate the shims' position, and remove the shims.

Apply wood preservative around the frame, and let it dry. Set a shim in the window frame corner. Mix the mortar to the thickness of bread dough for the best results.

Dip the trowel in the mortar. Brush mortar on the open side of the shim, and place another shim tightly against it. Repeat the process across the bottom of the frame using the marks as guides. Run a striker tool over mortar joints to even them.

Allow the mortar to dry. Repeat the process of setting shims and marking them on the frame sides. After the mortar dries for around two hours, smooth the joints. Wipe excess mortar with the cloth, and let the area dry for twenty-four hours.

Since mortar isn't used on the frame, install wood trim around it with a half-inch overlap on the blocks for a tight insulation. Apply a bead of silicone caulk on the inside and outside of the frame where it meets the blocks to seal it tight. Repeat on the outside of the frame, and allow the caulk to dry.

For more information, contact Fischer Window and Door Store or a similar company.