Blocks with large faces will let in more light, and thin blocks are better for windows. You can use different sizes, colors and textures to create the look you want.;
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Plan your project to use whole blocks. Glass blocks can't be cut.
Allow a space of ¼ to ⅜ inch (0.6 to 1 cm) between blocks and between the blocks and the wall, jamb or window frame. You must include the spaces for your drawing to be accurate.
You may discover that no arrangement of glass blocks will completely fill the area of the installation. Plan to add finished wood or other material to the arrangement.
 The amount of mortar you will need depends not only on the size of the project, but on the size of the blocks. Mix the mortar in batches that can be used in about an hour so the mortar won't start to set before you get a chance to use it.



Place the first block. Then, trowel enough mortar onto one side of the next block so that when you set it beside the first block, the mortar fills the space between and sticks the blocks together. Add mortar to only one side of each subsequent block in the row.
The spaces between the end blocks and the wall, jamb or window frame will be filled with an expansion strip, not mortar. The expansion strip will allow the blocks to expand and contract with changes in temperature.
 Tap the blocks snugly against the spacers with a rubber mallet. Spacers ensure that the spaces between blocks are uniform and that the weight of the upper rows don't force mortar to squeeze out of the lower rows.


Use "T" spacers around the perimeter. Press the first spacers into the mortar as the first row of blocks is installed. For the sides, screw or nail "T" spacers to the adjoining wall or window frame.
Place "X" spacers between blocks. They will ensure even spacing between blocks on the same row and between rows.
Put the spacers between blocks halfway between the back and front so they don't interfere with tooling the joints later. Leave them in place and mortar over them.



Lay a thin bed of mortar and press the reinforcing rod into it.
Connect the rod to the anchors. The anchors extend from the wall or window frame at least 1 inch (2 to 3 cm).
 Before the mortar sets, use a mason's jointer along all the spaces between the blocks to make the mortar joint smooth and concave.


Except for very small glass block installations, you will need to regularly stop and tool the joints. Don't wait until you're done laying the blocks.
 The dust that forms on the blocks as the mortar dries can be wiped away with a soft cloth later.
 Use regular caulk between the blocks and the wall or frame and clear silicon sealant between blocks.
Choose the right glass block for your project.
Draw a diagram of the installation.
Mix the glass mortar according to the directions.
Put down a bed of mortar and place the first row of blocks.
Place the appropriate spacers between the blocks.
Install anchors and reinforcing rods every 2 feet (0.61 m) (61 cm) to provide strength and stability to your glass block installation.
Tool the joints.
Clean any stray mortar off the faces of the blocks with a damp cloth.
Seal the perimeter and joints when the mortar is completely set.
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