CCS Chimney Cap & Crown Systems Flashcards

What is a chimney crown and where is it located?

Answer: The concrete or mortar slab that covers the top of the masonry chimney, surrounding the flue

The chimney crown is the concrete or mortar slab built over the top of the masonry chimney to shed water away from the flue, separate from the cap itself.

What is the recommended overhang for a properly built chimney crown beyond the face of the chimney?

Answer: At least 2 inches

A chimney crown should extend at least 2 inches beyond the chimney face to direct water away from the masonry and prevent moisture infiltration.

Which crown defect is most commonly found during a chimney inspection?

Answer: Cracks or spalling in the crown surface

Cracking and spalling are the most common crown defects, caused by freeze-thaw cycles that allow water to penetrate and break apart the crown material.

What product is commonly used to seal hairline cracks in a chimney crown without full replacement?

Answer: Elastomeric crown sealer or sealant

Elastomeric crown sealers are flexible coatings that bridge hairline cracks and resist further freeze-thaw movement without the need to rebuild the crown.

A chimney crown should be constructed with which type of mix to ensure long-term durability?

Answer: Portland cement-based mix (not mortar mix)

Portland cement-based concrete is required for crowns because standard mortar mix lacks the strength and water resistance needed to withstand outdoor exposure.

Why must a gap be left between the flue liner and the chimney crown?

Answer: To accommodate thermal expansion of the flue liner without cracking the crown

Leaving a gap (often filled with a flexible caulk) between the flue liner and crown prevents the thermally expanding liner from cracking the crown.