Chimney Cap vs Chimney Crown: What Is the Difference?
Caps and crowns protect the top of your chimney differently. Here is what each does.
Reviewed by John Freeman, chimney and fireplace professional with 20+ years of field experience.
Last updated
Short Answer
The crown is the sloped concrete or mortar slab across the top of the chimney that sheds water off the masonry. The cap is the covering over the flue opening that keeps out rain, animals, and debris. The two terms get mixed up because the Oregon Residential Specialty Code calls the sloped top slab a cap, while the chimney trade calls it the crown and uses cap for the cover above the flue.
Crown and Cap Side by Side
| Feature | Crown | Cap |
|---|---|---|
| Where it sits | Across the top of the chimney, around the flue liner | Over the flue opening |
| Made of | Concrete, metal, or stone (code); mortar or concrete is typical | Metal or masonry (code) |
| Job | Sheds water away from the flue and the masonry | Keeps rain, animals, and debris out of the flue; a spark arrestor screen also keeps embers in |
| What the code says | Sloped to shed water, with a drip edge and a caulked bond break around the flue liner | If a rain cap is installed, the open area under it must be at least four times the flue outlet area. A spark arrestor needs the same four-times area. |
| Typical failure | Cracks, crumbling, no drip edge, no gap around the liner | Rust, a missing or crooked cap, a blocked screen |
| How it shows up | Water streaks down the chimney, damp masonry, water in the firebox | Rain in the flue, nests or debris, smoke backing up if the screen clogs |
What the Crown Does
Without a crown that sheds water, rain runs into the top of the masonry and down inside it. The code calls for a slope, a drip edge so water falls clear of the chimney sides, and a caulked bond break between the crown and the flue liner. The Chimney Safety Institute of America (CSIA) says NFPA 211 requires that bond break where the top tile passes through the crown, so the flue can expand vertically, and notes it is rarely included in the original construction. CSIA's inspection procedure also calls the crown the wash, and checks it along with the flashing and any cricket.
What the Cap Does
The cap covers the flue opening against rain and debris and keeps birds and animals out. CSIA lists animal and bird nests among the blockages that can force toxic gases back into a home. The cap must not choke the flue itself: the code requires the open area under a rain cap, and under a spark arrestor, to be at least four times the area of the flue outlet. A spark arrestor screen must have openings that do not pass a sphere larger than 1/2 inch and do not block a sphere smaller than 3/8 inch, and it must be removable for cleaning. CSIA inspects top accessories for rust, corrosion, blockage, and moving parts that no longer work.
Chimney Height
A chimney also has to be tall enough. The code requires it to extend at least 2 feet higher than any part of the building within 10 feet, and at least 3 feet above the highest point where it passes through the roof. A chimney that falls short of that rule is a candidate to look at when smoke or draft problems show up in wind.
Why a Coating Does Not Replace Either One
The Brick Industry Association (BIA) says water-repellent coatings cannot stop water penetration caused by deficiencies such as ineffective caps or copings or incompletely filled mortar joints. A failed crown or a missing cap has to be repaired or replaced. A coating applied over it does not make up the difference.
Next Step
Cap and crown condition is part of a chimney inspection and a sweep, and it can often be assessed from photos. If you are in Southern Oregon, send photos of the chimney top for a free review, or book a $99 inspection. The right fix depends on how far the damage goes, and we explain the options in writing before any work.
Sources
- Oregon Residential Specialty Code (2023), Chapter 10: Chimneys and Fireplaces
- CSIA Standard Operating Procedure: Level 1 Inspection, Masonry Fireplace
- CSIA Standard Operating Procedure: Level 2 Inspection, Masonry Chimney
- Chimney Safety Institute of America: Avoiding Carbon Monoxide Hazards
- Brick Industry Association, Technical Note 6A: Colorless Coatings for Brick Masonry
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