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Chimney Crown: Repair, Resurface or Replace?
A cracked crown does not always need to be torn off. Whether it can be repaired or resurfaced, or needs to be rebuilt, depends on what the crown is made of, what shape it is in and whether it is doing its job.
What a crown is supposed to do
The crown is the slab across the top of a masonry chimney that sheds water away from the flue and the brick below. If you are unsure how it differs from the cap, see crown vs cap vs chase cover. This guide is about the decision once you know the crown is damaged.
Home-inspection training material says crowns should be Portland cement-based, slope to shed water and overhang the chimney by at least 2 inches. The same material warns that mortar at the crown is not durable and tends to crack, and flags crowns whose slope directs water into the flue. A model residential code calls for a concrete, metal or stone cap with a drip edge and a caulked bond break around the flue liner, sloped to shed water. The Brick Industry Association calls the crown area “often overlooked as a source of moisture penetration.”
Why a damaged crown matters
Water that gets through the crown can reach the brick, the mortar and the flue. The CSIA white paper on chimney fires notes that frozen water admitted by a poor crown can damage clay liners. Water in the brick can lead to the problems in spalling brick and freeze damage and the leaks in why is my chimney leaking.
How a professional decides
A crown is hard to judge from the ground, so it is assessed up close. CSIA inspection guidance includes checking the crown (the wash) and flashing as part of the exterior review. The questions that usually decide between repair and replacement are:
- How widespread is the damage? A few hairline cracks are a different situation from large cracks, missing chunks or a surface that is crumbling.
- Is the crown still sloped correctly? If it holds water or sheds it toward the flue, a coating over it will not fix the shape.
- Is it the right material? A crown made of thin mortar may not be worth repeatedly patching.
- Does it overhang the chimney by the recommended amount?
- Is the flue tile free to move? CSIA Level 2 guidance refers to a break where the top tile passes through the crown, so the flue can move vertically.
- What is under it? If the brick or mortar below is also damaged, the work may extend to repointing or a partial rebuild.
Repair or resurface vs replace
| Repair or resurface | Replace | |
|---|---|---|
| Usually considered when | The crown is mostly sound, with limited cracking and correct slope | The crown is badly broken, poorly shaped, too thin or missing its overhang |
| What it involves | Filling cracks and applying a new surface or protective coating to the existing crown | Removing the old crown and forming a new sloped one, with a proper break around the liner |
| Trade-off | Less work, but it relies on what is underneath being sound | More work, but it can correct shape, slope and overhang |
Our chimney crown repair service covers this work. Our Montclair project began with hairline cracks in the crown, which were resurfaced and weatherproofed, with a new cap added. The Tinton Falls project began with a Level 1 inspection and included crown, flashing and stucco work.
Other work that often goes with the crown
- A new cap, since the cap and crown protect the chimney together.
- Flashing repair, because the crown and flashing are both main places water can enter.
- Waterproofing of the brick below.
- Repointing where joints are open.
For scope and price questions, see understanding a chimney repair quote.
Frequently asked questions
Can I fix crown cracks with caulk?
Caulk or a thin sealant may be part of a repair, but the right fix depends on the damage. A professional should look at the crown first, particularly because a bad slope or an open crack to the flue will not be solved by sealing the surface.
How can I tell if the crown is cracked?
From the ground it is hard to be sure. Stains on the brick below, flaking mortar, or water in the fireplace can be signs. Do not climb onto the roof to check it yourself; a professional can photograph it.
Is a crown repair a permanent fix?
It depends on the condition of what is underneath and the cause of the cracking. Ask what is being done to prevent the crack from returning.
Next step
Request an inspection or call (862) 225-6529. AM Chimney Sweep is a registered (NJ HIC #13VH14312300) and insured New Jersey home improvement contractor.
Sources
- InterNACHI, How to Inspect Fireplaces, Stoves, and Chimneys (crown mortar cracks, Portland cement-based, slope, 2-inch overhang)
- Model residential code text (R1003.9.1), via GoCodeBook (cap or crown with drip edge, caulked bond break per ASTM C1283, sloped to shed water; this is the California adoption, shown as an example of the model code)
- Brick Industry Association, Flashing Chimneys (crown area often overlooked as a source of moisture)
- CSIA, Chimney Fires: Causes, Effects and Evaluation (frozen water from a poor crown can damage liners)
- CSIA, Level 2 Inspection of a masonry chimney (inspecting the crown and flashing; break at the top tile through the crown)