Cracked chimney masonry repaired in Ventura

When joints need to be cut out and repointed

Five conditions, listed in brick industry guidance, call for repointing rather than surface treatment. We check for each of them during the inspection, joint by joint, on every face of the chimney we can reach.

• Mortar eroded back more than about a quarter inch
• Mortar that crumbles when scraped
• Voids in the joints
• Hairline cracks in the mortar
• Cracks between the brick and the mortar

Dampening the joints before filling

Joints are dampened before repointing, under brick industry guidance, while letting the brickwork absorb all surface water so the mortar can bond. Dry, thirsty brick pulls water out of fresh mortar too quickly, and a wet, glistening joint weakens the bond.

Getting that balance right depends on the brick and the day. We judge it on site rather than following a fixed routine, especially on a sunny chimney top. In strong sun, that may mean dampening the joints more than once as the work moves across the chimney.

The mortar types named in ASTM C270

ASTM C270 sorts mortar for unit masonry into types, and Technical Note 8B summarizes them. Your estimate names the type we propose for your chimney and explains why it suits the brick and the existing joints.

• Type M, high compressive strength but not very workable
• Type S, all-purpose with higher compressive and flexural bond strength
• Type N, all-purpose with good bonding and workability
• Type O, low strength, used mostly inside and for restoration

Loose courses at the top of the chimney

The top courses of a chimney take the brunt of the weather and carry little weight above them to hold them in place. When their joints fail, bricks can loosen and fall.

If you see loose brick at the top, keep people and vehicles clear of the area below, and do not climb up to check. We inspect from a safe access point, remove material that could fall, and then plan the repair or rebuild of that section.