How to Repair Crumbling Mortar Joints

Mortar acts as the connective tissue of your home, holding bricks or stone in a rigid, weather-resistant embrace. Over time, moisture infiltration and the natural settling of a house cause this material to turn to dust, leaving unsightly gaps that invite water inside. When you see cracks or missing sections, addressing them quickly is not just about aesthetics—it is about preventing structural water damage that can compromise your entire masonry wall. Repointing, or tuckpointing, is the professional process of replacing this degraded mortar with fresh material. Done well, the new mortar will match the texture and color of the original, creating a seamless seal that sheds water efficiently. This project requires patience and a steady hand, but it is one of the most effective ways to extend the lifespan of your exterior brickwork.

  1. Chip Away Crumbling Mortar. Use a hammer and a masonry chisel to chip away the crumbling, loose mortar to a depth of at least 3/4 inch. Ensure the cavity is deep enough to provide a solid foundation for the new mortar to bond.
  2. Scrub the Cavity Clean. Use a stiff wire brush to scrub the exposed brick edges, removing all dust, grit, and loose debris. Follow up with compressed air or a high-pressure garden hose to ensure the surface is completely free of loose particles.
  3. Achieve Perfect Peanut Butter. Mix your Type N or Type S mortar powder with water in a small mortar tub until it reaches the consistency of firm peanut butter. Avoid adding too much water, as a soupy mix will sag and weaken as it dries.
  4. Pack Mortar Tight. Use a mortar bag or a tuckpointing trowel to force the fresh mortar into the cavity. Pack it tightly against the back and sides of the bricks to ensure there are no air pockets.
  5. Shape the Joint Profile. Once the mortar loses its sheen and feels thumbprint-firm, use a jointing tool to press it into the desired profile, such as a concave or flush finish. This step compresses the mortar and creates a smooth, water-shedding surface.
  6. Brush and Cure Slow. Wait for the mortar to dry until it is crumbly, then lightly brush away any excess material from the brick faces with a soft-bristle brush. Keep the area shaded and lightly mist the mortar with water for the next two days to ensure a strong, slow cure.