Loose chimney brick and open joints repaired in Aloma

Only breathable products on exterior brick

Exterior brickwork should only receive water repellents that let water vapor pass, such as silanes and siloxanes. Brick industry guidance adds that film-forming coatings should not be applied to exterior brick at all.

A film traps moisture inside the masonry, where it can do more damage than rain on the surface. If your chimney already carries a film coating, we explain what it means for the repair and how we deal with it. Removing an old film coating is sometimes part of the repair, and when it is, the estimate describes the method and the area.

Offsets in a clay-lined chimney

Section R1003.7 of the residential code limits the offset of a masonry chimney built with a fireclay liner surrounded by one wythe of masonry. The centerline of the flue above the offset may not extend beyond the center of the chimney wall below it.

Offsets are part of the original construction, not something a repair should change. When we rebuild a section that includes one, we lay it back to the same geometry and tell you if the existing offset raises a concern. Rebuilding an offset also takes more care in support while the new courses cure, and the estimate reflects that.

Things that keep chimney masonry wet

Masonry dries between rains when it can. A gutter spilling against the chimney, a sprinkler aimed at its base, soil or mulch piled against the lower courses and plants holding moisture on its face all stop it drying.

We point out those sources when we see them. They are usually simple to change, and changing them gives the repaired masonry a far better chance than new mortar alone. Where the source is a failed crown, cap or flashing rather than something in the yard, we write that repair up as its own line.

What a masonry estimate should list

Our written masonry estimates list the parts of the job that decide price and result, so you can compare them fairly with any other proposal.

• The repair area, marked from sound to sound masonry
• The mortar type and how it matches the existing joints
• Replacement brick, if any, and the expected match
• Removal of old patches, sealant and loose material
• Access, roof protection and cleanup
• Separate lines for crown, flashing or other work