It’s been said that a chimney without a crown is like a house without a roof.
Most homeowners never think about masonry chimney maintenance beyond the occasional flue cleaning. Although a chimney may seem like a relatively simple structure, several important components must work together to keep a fireplace system in good working order. One of the often forgotten yet critical pieces of the system is the chimney crown.
Here’s what the building code says about the crown’s construction.
Chimney Crown Construction
International Residential Code – 2113.9.1 – Chimney Caps
Masonry chimneys shall have a concrete, metal, or stone cap, a drip edge, and a caulked bond break around any flue liners in accordance with ASTM C1283. The concrete, metal, or stone cap shall be sloped to shed water.
International Residential Code – 2113.9.2 – Spark Arrestor
A spark arrestor shall meet all of the following requirements:
- The net free area of the arrestor shall be not less than four times the net free area of the outlet of the chimney flue it serves.
- The arrestor screen shall have heat and corrosion resistance equivalent to 19-gage galvanized steel or 24-gage stainless steel.
- Openings shall not permit the passage of spheres having a diameter greater than 1/2 inch (12.7 mm) nor block the passage of spheres having a diameter less than 3/8 inch (9.5 mm).
- The spark arrestor shall be accessible for cleaning and the screen or chimney cap shall be removable to allow for cleaning of the chimney flue.
Chimney Crown Maintenance
As you see in this video, over time, the crown may develop cracks. The cracks in this crown have reached a critical point. If not repaired soon, rainwater could leak into the firebox below or, even worse, work its way into the ceiling.
Some handyman services and chimney sweep contractors make repairs by covering the crown with a flexible elastomeric coating. The coating will help stop existing cracks from spreading and can help prevent new ones from forming.
I do not inspect inside the chimney flue. Call a Chimney Safety Institute of America – CSIA approved Chimney Sweep to perform level 1, 2, or 3 inspections.
CREOSOTE – If you use a wood-burning fireplace, creosote is NOT your friend. It’s a tar-like substance that sticks to the inside of your chimney. Creosote is corrosive and can deteriorate brick mortar. If not kept cleaned out of the chimney flue, this byproduct of wood combustion is a serious fire hazard.Gary Smith – Construction Coach – Professional Home Inspector
Three Chimney Inspection Levels
The National Fire Protection Association (NFPA) 211 identifies three levels of inspections for chimneys, fireplaces, vents, and solid fuel-burning appliances.
The Level 1 inspection requires removing the damper plate for viewing the interior surface of a fireplace smoke chamber. This inspection type is conducted when the chimney is swept, for example, during a basic annual inspection.
A Level 2 inspection, the most common dheck-up, is normally conducted during real estate transactions. The chimney sweep would inspect the chimney and the interior surfaces of the flue by using closed-circuit video equipment.
Level 3 inspection is rarely performed and entails all portions of the Level 1 and Level 2 inspections and gaining access to concealed areas of the chimney. This inspection requires some dismantling or destruction of parts of the chimney.
Watch this video.