Chimney masonry repair for Hyde Park homes

Sealing hairline cracks in mortar joints

Fine cracks in otherwise sound mortar can sometimes be sealed without cutting the joints out. BIA describes face grouting with a thin mix of portland cement, lime and fine sand, brushed into dampened joints, usually in two coats.

The trade-off is appearance. BIA notes that grouted joints tend to look slightly wider and less textured, because the sand in the old mortar is covered.

We show you where face grouting would work on your chimney and where the joints need more than a surface treatment.

Signs that chimney joints need repair

BIA's maintenance note gives a short list of joint faults worth repointing. It includes erosion past roughly a quarter inch, mortar that crumbles, hollow voids, fine cracking, and separation along the edge of the brick.

Checking is simple for a mason. A look along the joints and a light scrape with a metal tool show whether the mortar is sound or powdery. Joints on the face of the chimney that takes the most rain often wear first, so each face is checked on its own.

Our crew does that check course by course on the parts of the chimney we can reach, and notes where the joints are still sound.

Matching the joint profile and color

The National Park Service asks that repair mortar match the original in color, texture and tooling, not only strength. Sand is the largest ingredient in mortar, so it controls much of the color and texture.

Joint profile matters too. A concave joint, a flush joint and a raked joint all read differently on the same brick. Where earlier repairs used a different profile, we match the original joints rather than the later patches.

We match the profile of your existing joints and explain how the new mortar will look as it weathers.

What your chimney masonry estimate should show

A masonry estimate is easier to trust when it answers specific questions about the work. Ask any contractor, including us, to spell these out.

• Which areas of the chimney will be repaired, and which are sound?
• Which bricks will be replaced, and which joints repointed?
• Which mortar type will be used, and why?
• How deep will old mortar be removed?
• How will the joints be finished, and how will the color be matched?
• What is being done about the crown, the flashing and the water source?