These get used interchangeably, including by contractors, and it makes quotes hard to compare. They are different parts doing different jobs.
The crown
The crown is the slab that covers the top of the masonry, around the flue tiles. Its job is to shed rainwater away from the brickwork below it, the way a windowsill sheds water away from a wall.
A proper crown is cast concrete, two inches or more thick, sloped away from the flue, and — the part that is almost always missing — overhanging the brick face by an inch or two with a drip edge underneath so water falls clear instead of tracking back down the masonry.
What most older Connecticut chimneys actually have is a mortar wash: a thin skim of mortar troweled over the top by whoever built the stack. Mortar is not a weatherproofing material, it is thin, it has no reinforcement and no overhang, and it cracks within a few years. Every one of those cracks funnels water into the core of the chimney.
The cap
The cap sits over the flue opening itself. Stainless or copper, with a lid and a mesh screen, anchored to the crown or into the flue tile. It keeps rain out of the flue, animals out of the stack, sparks off the roof, and downdraught out of the room.
Side by side
| Crown | Cap | |
|---|---|---|
| What it is | Cast concrete slab | Stainless or copper lid |
| Covers | The masonry top | The flue opening |
| Protects against | Water into the brickwork | Water, animals, sparks, downdraught |
| Typical failure | Cracking, no overhang | Rusting through, blowing off |
| Fixed by | Crown coat sealing or recasting | Replacement |
How each one fails
Crowns crack. Hairline first, then wider through freeze–thaw, then a section lifts. Caught early, a flexible crown coat — an elastomeric sealer that bridges hairline cracks and stays flexible through temperature swings — will extend its life considerably. Left long enough, it needs recasting, which means removing the old crown and forming a new one properly.
Caps corrode or depart. Galvanised ones rust through and then funnel rust down the brick. Poorly anchored ones come off in wind, and the first anyone knows is water in the firebox.
Which do you fix first?
If both are gone, the cap is quicker and cheaper and stops the most immediate problem — water going directly down the flue. But if the crown is badly cracked, capping alone leaves water pouring into the masonry, and that is the damage that turns into a rebuild. In practice they are usually done in the same visit, because both need roof access and that is the expensive part of either job.
Which one you need
A cracked or flat crown is crown repair or replacement. An unprotected flue opening is a cap. A chimney that has been leaking for a few years is frequently both, and ABC Chimney Solutions will say so rather than quoting one and letting you find out. There are photographs of crowns we have rebuilt on the projects page.
Frequently asked
Can I repair a cracked crown myself?
A crown coat product applied to a crown with hairline cracks is within reach of a competent, comfortable DIYer — the material is straightforward. The parts that are not are working safely at height and judging whether the crown is a candidate for sealing or past it. ABC Chimney Solutions sees a lot of sealed crowns that needed recasting, and sealing one only hides it for a season. Learn more about this service.
How much overhang should a crown have?
An inch to two inches beyond the brick face, with a drip edge cut underneath. Without the drip edge, water follows the underside of the overhang back to the masonry by surface tension and the overhang achieves nothing — which is the detail ABC Chimney Solutions most often finds missing. Learn more about this service.
Is a chase cover the same as a crown?
Same job, different construction. A chase cover is the metal lid on a framed chase around a factory-built fireplace, where a masonry chimney would have a cast crown. It fails by rusting through, and ABC Chimney Solutions replaces them in stainless, measured to the chase — look for rust staining running down the outside. Learn more about this service.