Slate flooring has gained popularity in contemporary design. Although the slate tiles should last many years, over time the grout can break down or stain and need to be replaced. Replacing the grout in slate floors is particularly important in areas with high moisture, such as a shower stall, which can cause the slate to separate from the base and crack.
Step 1: Remove the old grout. To complete this step in a timely manner, purchase a bit to remove grout that will fit a cordless drill. Then use this tool to carefully remove the grout while wearing safety glasses.
TIP: To use the grout bit, use the narrow edge of the bit to carefully remove the grout. Start from the center of the grout line, using the bit to remove the grout. Then, after the first pass in that area, you can use the bit to expand the line and remove the rest of the grout.
Step 2: Vacuum as you go, removing the grout dust with a shop vac. This will ensure that you can see how much grout should be removed.
Step 3: Use a stiff bristled nylon brush to clean out the crevices between the slate tiles, then vacuum one last time.
Step 4: Mix sandless grout with water, following the proportions recommended by the manufacturer. Too much or too little water could cause the grout to prematurely crumble. You may have to mix the grout in batches: you should never mix more grout than you can use in 20 minutes.
Step 5: Use a rubber float to push the sandless grout into the cracks of the slate. Wait 10 minutes to allow the grout to harden slightly before continuing.
Step 6: Remove any grout that is on the surface of the slate with a sponge. Buff the surface of the slate with a rag to remove any grout haze.
Step 7: Allow the grout to dry at least a full day before walking on it. After a couple of days, you can clean the slate once more and seal it to prevent grout staining.