Masonry
Repointing or rebuilding a chimney?
Two very different repairs get mixed up. Knowing which one applies helps you read a quote.
Short answer. Repointing replaces worn mortar joints and leaves the brick in place. Rebuilding takes down and relays sections of brick. If the brick is sound and only the mortar has failed, repointing is usually the right scale of repair. If brick and structure have failed, rebuilding is the honest answer.
What each one is
Repointing means cutting out deteriorated mortar to a sound depth and filling the joints with new mortar. The National Park Service guidance on repointing says to remove old mortar to about two to two and a half times the joint width, which is roughly a half to one inch for typical brick joints.
Rebuilding means taking down the affected part of the chimney, often from the top down, and rebuilding with brick.
Which one fits?
| Condition | Usually points to |
|---|---|
| Mortar sandy, recessed or missing; brick sound | Repointing |
| A few damaged bricks, joints otherwise sound | Brick replacement plus repointing |
| Many bricks spalled or cracked through | Replace bricks, or rebuild if widespread |
| Chimney leaning or sections loose | Rebuild the affected portion |
| Only the top courses are bad | Rebuild the top section |
Why the mortar matters
Mortar is supposed to wear before the brick does. The National Park Service guidance explains that if repointing mortar is harder and less permeable than the brick, moisture moves out through the brick, and the brick faces spall. Repointing mortar should therefore be softer than the brick units. It is a fair question to ask any mason about the mortar they plan to use.
Related
Water entering the masonry is the underlying cause in most cases. See Why is water coming into my chimney?.
Sources
Common misconceptions
"Caulk is a cheap fix." It is not a substitute for mortar.
"Any mortar will do." Mortar should suit the brick it joins.
About this guide. Published by Dr. Sweeper as general homeowner education, last updated October 1, 2026. Sources are linked where they are cited. What applies to your home can depend on your local building code, your appliance and its manufacturer's instructions, and the actual condition of your chimney, so this guide is not a substitute for an inspection.
If you need help
Related services
Repointing
Replacing deteriorated mortar joints.
Learn moreCrown repair
Repair of the cement or masonry top of the chimney.
Learn moreChimney inspection
A condition check of the chimney system.
Learn moreBrick & Masonry Repair
Spalled, cracked or loose brick.
Learn moreChimney Rebuild
When repair will not hold.
Learn morePartial Chimney Rebuild
Rebuild only the failing top section.
Learn moreReady to have your chimney looked at?
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