Does an Outdoor Fireplace Need a Chimney Cap?

Two Things Called a Cap

The word covers two parts. Section R1003.9.1 of the 2023 Florida Building Code, Residential, requires every masonry chimney to have a concrete, metal or stone cap, with a drip edge and a caulked bond break around the flue liner, sloped to shed water; many people call that part the crown. The metal hood that sits over the flue opening is a rain cap, and section R1003.9.3 requires at least four times the flue's open area underneath it so it does not choke the draft.

An outdoor chimney needs both. The first keeps water out of the masonry, the second keeps it out of the flue and the firebox.

Rain Into an Open Firebox

Indoors, a damper closes the flue between fires. Outdoors there often is none; one factory-built outdoor fireplace manual says plainly that the unit has no flue damper. Rain falls straight down an uncapped flue into the firebox, soaking the ash and the refractory, and that same manual notes the unit sheds moderate amounts of water but is not waterproof.

Factory-built units come with the answer. Unilock notes that pre-built outdoor fireplaces include a factory-made stainless firebox, pipe and metal termination cap, and the outdoor fireplace manual requires a cap approved and listed for that fireplace system, not a generic one.

Spark Arrestor Screens Near Trees and Screen Rooms

The code does not require a spark arrestor on a masonry chimney, but section R1003.9.2 sets four rules where one is installed:

• Its open area is at least four times the open area of the flue it covers.
• The screen resists heat and corrosion at least as well as 19-gage galvanized steel or 24-gage stainless steel.
• The mesh stops anything larger than 1/2 inch and passes anything smaller than 3/8 inch.
• It can be reached for cleaning, and the screen or cap comes off so the flue can be swept.

Metal That Lasts Outdoors

An outdoor cap lives in rain and humid air, so the metal matters. The code's screen rule sets the floor at the corrosion resistance of 19-gage galvanized or 24-gage stainless steel,. The outdoor fireplace maker also tells owners to paint the termination cap with a rust-resistant paint to protect the parts exposed to weather.

Placement counts as well. That manual asks for the cap to sit where it will not be plugged and away from trees or other structures, with its bottom at least 3 feet above a roof it passes through and 2 feet above any roof within 10 feet. Near a screen enclosure or overhanging oaks, a working spark screen is worth having even where the code does not require it.

Cleaning Under the Cap

Caps catch what blows into them. The outdoor fireplace manual lists birds' nests and leaves in the termination cap as a cause of a fire that smokes or will not light, and shows how each style of cap comes off for chimney cleaning. It also warns that the cap must overlap the chimney pipe by the specified amount, or the two can separate and let sparks, heat and embers escape.

NFPA 211, as quoted in national chimney safety guidance, calls for chimneys to be inspected once a year, noting that animals may nest in a flue even when it is not used. Replacing a rusted, bent or missing cap is chimney cap replacement. Our family-owned company is locally run, its experienced roof crew does the work, and every job begins with a free inspection and a written estimate. We are Proudly American, and a Proudly American crew fits a cap sized to the flue, not a guess.