How to Make a Frame Around an Exterior Glass Block Window

Measure the opening of the window. Sketch the opening on a piece of graph paper. Use the measurements of your glass block to determine how many glass blocks to use to fill the opening. The blocks are slightly smaller than the dimensions by which they are sold in order to allow space for mortar. Calculate that extra space within the opening.

Frame in the window the bottom portion of the window to match the space necessary for the glass block. At the window's bottom, hammer in one piece of framing wood that matches the width and length of the window opening. Use 16-penny framing nails.

Check the measurements after you add the wood to ensure you do not close in too much of the area. Make adjustments if necessary.

Add framing wood to the sides of the window opening, and then to the window's top as necessary until the area conforms to the space needed by the glass block.

Paint the surface of the framing wood with a wood preservative. Allow it to dry.

Insert the glass block by following the manufacturer’s instructions for mortaring.

Cut 1/2-inch thick wood trim molding at a 45-degree angle with a miter saw. The molding will fit against the glass block window inside and outside the home, holding the window in place. Nail the wood trim molding into the framing wood with a nail gun using 3/4-inch long trim nails.

Apply caulk between the glass block and the wood trim on the exterior and interior of the glass block window.