How can I repair crumbling bathroom tile grout?
Clean the surface that needs grout change then using a grout saw, remove the existing crumbly grout. Vacuum the debris to make sure everything is clean before adding the new grout. Prepare your grout mixture (best option for bathroom floor is SnapStone Urethane Flexible Grout) Using a margin float, apply grout on the floor. You want to make sure the gaps are being covered by pushing the grout mix in using a rubber grout float. Let the joints settle and dry before wiping it with a damp sponge. If you see any haze on your floor, just buff it off with a wet towel/cloth.