How to Build a Block Window

Measure the width and height of the window opening with a measuring tape to determine the number of glass blocks you need. Check the bottom of the window frame with a carpenter's level to ensure that it is level.

Apply mortar to the bottom of the window frame with a trowel. Embed spacers into the mortar where the corners of each block that makes up the bottom course will sit.

Install the first course of glass blocks on the mortar bed, installing spacers and spreading mortar between each block with a trowel, and between the blocks and the sides of the frame.

Continue installing block courses until you reach the top of the window. Check each course with a carpenter's level to ensure that it is vertical. Spread mortar on top of the final course of blocks before installation.

Brush away excess mortar from the blocks on both sides of the window with a wire brush. Strike the mortar between the blocks and along the perimeter of the window with a jointer to create a smooth indentation.

Load a caulk tube into a caulk gun and snip the end of the tube with scissors. Squeeze the handle of the caulk gun and apply caulk along the perimeter of the glass block window on both sides.