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How to Replace Glass Block Window Grout With Silicone Caulk

Robert Sylvus

Glass block grout contains pores that trap moisture and debris, such as soap scum and cleaner residue. Over time, the contaminants stain the grout, often changing the grout from bright white to dull yellow. The glass block grout's rough surface wears holes in cleaning rags or sponges, leaving small particles on the grout's surface. Some glass block applications use a silicone caulking as a sealant instead of grout. Replacing a glass block window's grout with silicone caulk gives the joints a smooth texture that repels contaminants.

Silicone caulking gives a glass block windows a smooth-textured joint.

Step 1

Lay a drop cloth on the floor below the glass block window. Cover the walls surrounding the window with plastic sheeting, using masking tape to hold the plastic against the wall.

Step 2

Cut a groove along the center of each glass block grout joint with a handheld grout saw. Run the grout saw across each horizontal and vertical grout joint until the saw's handle reaches the joint. A handheld grout saw's blade uses a carbide tip to grind through the grout's surface.

Step 3

Score the edge of each grout joint where the grout touches the glass block with a utility knife, using the knife blade to create a ¼-inch-deep ridge in the grout along each edge of each glass block.

Step 4

Hold a cold chisel's blade on the grout's ¼-inch-deep ridge and angle the chisel toward the groove cut in the center of the grout joint. Lightly tap the chisel's handle with a hammer until the grout at the end of the chisel releases from the joint. Use care to keep the chisel off the glass block. Remove all the grout using this method.

Step 5

Clean the glass block window with a stiff bristle brush and white vinegar, removing all the small grout particles the utility knife and chisel missed. Wash the vinegar from the glass block with a sponge dampened in clean water. Let the glass block dry completely before continuing.

Step 6

Place a tube of silicone caulking in a caulking gun. Cut ¼ inch off the tip of the caulking tube with the utility knife.

Step 7

Hold the caulking gun at a 45-degree angle to the glass block window and place the tip of the tube of caulking in the glass block's grout joint. Squeeze the caulking gun's trigger, forcing silicone caulk out the end of the tube. Fill each glass block grout joint with the silicone caulk.

Step 8

Run a grout edger's curved end across the silicone caulking in the horizontal joints, creating an even caulk joint with the tip of the tool. Clean the excess caulking from the tip of the grout edger with the sponge when needed.

Step 9

Run the grout edger down each vertical joint, working from the top of the joint toward the bottom. Clean the excess caulking from the grout edger with the sponge as needed.