Our Process

The craft behind repointing a chimney in Midway

Mortar conditions that call for repointing

Five conditions warrant repointing, according to Brick Industry Association Technical Note 46: mortar eroded more than 1/4 inch deep, crumbling mortar, voids in the mortar, hairline cracks within the mortar and cracks where brick meets mortar. Each of them can let moisture into the masonry.

During the free inspection we check each face of the chimney for those conditions, from the lowest visible course to the courses under the crown. Joints that are only weathered on the surface can often stay. Joints that are open, hollow or soft are marked for repointing and included in the written estimate.

Matching the original chimney mortar

For the best match, the Brick Industry Association recommends duplicating the original mortar's ingredients and proportions, and where the type is unknown, sending samples to a testing laboratory. ASTM C1324 is the test method generally used to examine hardened mortar and estimate its proportions.

Most homeowners do not need a laboratory report to repoint a chimney. Where the brick is old, soft or unusual, though, an analysis can be the safer route, and we will say so and explain how it affects the schedule. Either way, the mortar decision is made before the first joint is cut.

Joint profiles that shed rain

The shape of the finished joint matters on an exterior chimney. Technical Note 7B names concave, V and grapevine joints as the profiles that best resist water penetration in exterior brickwork, because tooling presses the mortar against the brick and leaves a dense, weather-tight surface.

Repointing normally matches the existing profile so the repair blends in. If the existing joints are a raked or flush style, which the same note lists for interior masonry, we discuss whether matching them or switching to a concave or V profile suits the repointed area. The choice is yours, and it goes on the estimate.

Softer mortar for older brick

Early masonry mortars were mostly lime, with little or no portland cement, and had lower strength. Technical Note 8B concludes that repairing older masonry will likely call for a weaker mortar than new construction, noting that Type O is often used to repoint older brickwork while Type N may suit newer brickwork.

The principle holds at any age. The new joint should be the part that gives, rather than the brick. Our specialists match the mix to your chimney's brick and existing mortar, whatever year it was built, and explain the choice before work begins.