Chimney crown vs chimney cap

Chimney crown: The concrete or masonry top of the chimney structure that covers the entire top surface of the chimney brickwork. The crown protects the chimney walls from moisture penetration. A properly-built crown projects beyond the brick edges (creating a drip edge) and slopes from the flue outward to shed water. Cracks in the crown allow water to enter the chimney structure, freezing and causing brick spalling and structural deterioration.

Chimney cap: A smaller metal covering installed over the flue opening itself (the actual smoke exhaust passage). The cap prevents rain, snow, and debris from entering the flue, and prevents animals (squirrels, raccoons, birds) from nesting in the chimney. Mesh sides of the cap also serve as a spark arrestor, reducing the risk of embers escaping and starting roof or vegetation fires.

For chimney sweep operators, both are common service items. Crown repair (typically using crown coat sealants or full crown replacement) is moderate-margin, periodic work. Cap installation/replacement is high-margin, quick service ($150-$400 for cap and labor). Operators should distinguish clearly when communicating with customers — many customers conflate the two terms and don't understand they protect against different risks. The recommended maintenance pattern: annual crown inspection, cap inspection at every cleaning visit.