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How to seal exterior brick

Updated February 21, 2017

Bricks offer a range of advantages as building materials, including classic aesthetic appeal, durability, fire resistance and energy efficiency. Seal exterior bricks to prevent damage caused by moisture such as efflorescence, flaking and separation of mortar and bricks. Siloxane brick sealers deeply penetrate the pores of bricks to create a chemical bond that shields the bricks while still allowing them to breathe. Non-glossy, siloxane sealers also will not compromise the natural texture or colour of the brick.

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  1. Repair and clean older brick walls before sealing. Chisel away any loose or crumbling mortar. Wash the bricks and mortar, scrubbing with phosphoric acid cleaner. Patch areas of excavated mortar with dry mortar pre-mix, using a point trowel. Smooth down the mortar joints with a jointer tool. Allow the mortar to fully cure.

  2. Mask any surrounding, non-masonry surfaces, using tape and plastic.

  3. Fill a hand-pump sprayer with siloxane brick sealer. Do not dilute unless the manufacturer recommends it. Pump the handle to build the pressure.

  4. Apply a light tack coat when sealing a wall. The tack coat is not necessary for floors. Pull the trigger to release a mist of sealer. Hold the nozzle at least 6 inches from the surface. Start at a corner (a top corner for walls) and work in left-to-right and up-and-down, continuously-moving, sweeping motions. Apply the sealer minimally, in slightly overlapping rows. Do not allow the sealer to puddle or drip.

  5. Apply a second, more generous "flood" coat. Begin with the flood coat, if sealing a floor. Work in the same manner as the tack coat but saturate the bricks with a greater amount of sealer.

  6. Apply one more coat of sealer if the brick is in an area that sees unusually large amounts of moisture.

  7. Tip

    Choose a day to apply sealer that is dry, with moderate temperatures. For smaller projects, you can use paintbrushes or rollers instead of a sprayer.

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Things You'll Need

  • Chisel
  • Hammer
  • Phosphoric acid cleaner
  • Scrub brush
  • Dry mortar pre-mix
  • Point trowel
  • Jointer tool
  • Tape
  • Plastic sheeting

About the Author

Mason Howard

Mason Howard is an artist and writer in Minneapolis. Howard's work has been published in the "Creative Quarterly Journal of Art & Design" and "New American Paintings." He has also written for art exhibition catalogs and publications. Howard's recent writing includes covering popular culture, home improvement, cooking, health and fitness. He received his Master of Fine Arts from the University of Minnesota.

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