How to Seal Exterior Tile Grout

Masons and do-it-yourself type homeowners install tile outdoors to cover patios, walkways and driveways. Grout lies between the tiles to fill in spaces and give the surface a uniform finished appearance. Sealing grout prevents the grout from staining. Cement-based grout requires sealing in outdoor spaces because the grout is somewhat porous. Sealers prevent mold penetration and growth. Stains, mold and mildew can only lie on top of the sealant.

Sealing exterior grout protects the surface.
  1. Sweep the surface to remove all dirt, dust and debris from the grout lines.

  2. Wash the grout surface with a mild detergent and scrub brush. Rinse the soap off the grout and allow the grout to dry completely. Remove areas of mold and mildew with a commercial mold killer. You can use an equal mixture of chlorine bleach and water to remove mold from white grout. Chlorine bleach may discolor or lighten colored grout.

  3. Apply an exterior-grade penetrating grout sealer with a small brush. Some sealers come with an attached brush application on top of the bottle.

  4. Allow the grout sealer to dry in accordance with the manufacturer's instructions, generally one to two hours. Apply a second coat of grout sealer and allow to dry.

  5. Test the sealer by pouring water on the grout. If the water beads up on the surface, the sealing is complete. If the water spreads, dry the area and apply another coat of grout sealer.


  • Grout sealers may darken the grout color.

About the Author

Sal Marco began writing professionally in 2009. He has written many online home improvement articles based on his more than 20 years of experience in the home improvement and building industries. He has worked as both part of a team and as a site supervisor. Marco has a Bachelor of Science in management science from Kean University.