Cracked chimney masonry repaired in Killarney

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

Airspace between the chimney and framing

Section R1003.18 of the residential code calls for at least 2 inches of airspace between combustibles and any part of a masonry chimney inside the building or within an exterior wall.

Masonry repairs must not fill that space with anything combustible, and rebuilt masonry must not be laid tight against framing. Where we can see the space, in the attic or at openings, we check it and note what we find, even when it sits outside the repair. Any framing found against the masonry is written up as its own item, since correcting it may involve other trades.

Staying safe around damaged masonry

Damaged chimney masonry is best inspected from a distance until someone has safe access. Do not climb onto the roof to look, and do not stand beneath loose brick to collect pieces.

A photo from the ground, taken from a safe spot, is plenty to start the conversation. Keep children, pets and cars away from the side of the house below any loose masonry until the chimney has been checked. If brick has already fallen, note roughly where it landed. It tells us which face and course it came from before we are on the roof.

Repointing only part of a chimney

Repointing a band or a single face rather than the whole chimney is common and often sensible. It does mean the new joints sit beside old ones, so the color match matters more.

Technical Note 46 advises matching the existing mortar color when only portions of a wall are repointed. We mix and compare samples first and set the boundary where the change will be least noticeable, such as at a corner or a course line. The new joints also weather toward the old ones over time, which helps the boundary fade.