Repair Cracked or Missing Tile Grout
Crumbling grout lets water reach the subfloor and causes much bigger damage. Re-grouting a tub surround or floor is a weekend fix anyone can do.
Scrape out old grout
Use a carbide-tipped grout saw or a rotary tool with a grout bit. Remove at least 2/3 of the depth of the old grout. Vacuum the grout lines clean.
Mix new grout
Mix sanded grout (for joints over 1/8") or unsanded (for thinner joints). Mix to peanut-butter consistency. Let it slake for 10 minutes, then remix briefly.
Apply with a rubber float
Hold the float at a 45° angle and press grout into the joints on the diagonal. Work in 3x3 foot sections so grout doesn't dry before you can wipe it.
Wipe with a damp sponge
After ~15 minutes, wipe at a 45° angle across the joints with a barely-damp sponge. Rinse the sponge constantly. Don't drag grout out of the joints.
Polish the haze after 2 hours
A thin haze of grout will form on the tile. Buff it off with a dry cloth. Let grout cure 24–72 hours per package instructions before exposure to water.
Seal (for cementitious grout)
Apply a penetrating grout sealer once cured. Prevents staining and mold. Not needed for epoxy grout.
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