Nothing can be more frustrating then discovering that you must replace a cracked glass block in your wall. Difficult, yet straight forward, most homeowners should be able to complete this project.
Step 1 - Preparing the Area
Using your grout saw, make a groove in the mortar around the glass block that you will be replacing. Typically this groove will need to be about 1/2 inch or more deep. Cut a groove on both the inside and the outside. This groove is essential as it helps to prevent damage to the glass blocks that are around the one that your are replacing.
Step 2 - Removing the Block
Using your hammer, tap a hole in the center of the glass block. Chip the glass away until you reach the mortar joints. Do this to both sides of the wall (If you are only able to access one side of the wall just follow the steps and only do it for one side). Make sure that you are wearing safety glasses and glove during this project.
Once you have tapped a hole in the center of the glass block, use a hammer and chisel to remove the mortar and any remaining glass. Be patient while doing this as not to damage any neighboring blocks.
If you find any plastic spacers in the corner you can cut those out with a pair of pliers.
Step 3 - Laying the Glass Block Mortar
Once you have removed the glass and mortar, clean up your work area. Make sure all the debris is gone from the hole, all loose material should be completely removed to allow the new glass block to sit properly.
When preparing the glass block mortar, the easiest approach is to pour a little water into a bucket then add the mortar. While you are using the margin trowel to mix, add more water until the mortar is the consistency of toothpaste.
Using your trowel, lay a bed of glass block mortar across the bottom of the hole. The top of the bed should be 1/2 inch tall. Lay two pencils across the bed of mortar.
Step 4 - Replacing the Block
Using your trowel, spread the sides and the top of the glass block with mortar. By doing this, it will prevent any gaps from showing.
Set the glass block into the hole, sliding it along the pencils until it is in place. The pencils help keep the bed of mortar in place. Once you have the block in place, you can remove the pencils.
Use a tuck pointer to fill in any space on the top and both sides of the glass block with glass block mortar. Continue to push mortar into the joints until they are filled. Do this on both the inside and the outside.
Step 5 - Cleaning Up
Once you have the glass block set, clean the glass block with a sponge and warm water until it is set. Be careful to not remove to much mortar from the joints while cleaning or it will not set properly.