Flues for Outdoor Kitchens and Pizza Ovens Under a Roof

Why the Roof Changes Everything

Out in the open, a wood-fired oven's short stack sends smoke up and away. Put the same oven under a pavilion, a lanai roof or an outdoor kitchen pergola with a solid top, and the smoke and heat collect against the ceiling, along with the sparks. The flue now has to pass through combustible framing and roofing to reach open air.

That is the case one oven maker's manual answers directly. It says the chimney connector shall not pass through an attic, roof space, closet or similar concealed space, or through a floor or ceiling, and that where an enclosure is combustible, only Class A chimney is used from the oven's anchor plate all the way to the termination outside.

Chimney Pipe Made for Solid Fuel

The same oven ships with an anchor plate for double-wall Class A stainless pipe meeting Standard HT 103, starting with a 24-inch section, and the manual warns that the chimney must be of a type suitable for solid fuel. Florida's residential code says the same of factory-built chimneys in a home: section R1005.3 requires those serving solid-fuel appliances to meet the Type HT requirements of UL 103, and R1005.1 has them installed and terminated to the maker's instructions.

Two more limits from that manual shape the route: the pipe may not bend more than 30 degrees in total, and extra 24-inch sections can be added, since the taller the stack, the further the exhaust is from the cook.

Clearances Around the Oven and Pipe

The oven maker's clearances to combustible materials are specific, and the manual warns that failing to keep them is a major cause of oven fires.

• At least 10 inches from the sides and back of the oven.
• At least 18 inches above the top and 30 inches below the bottom.
• At least 30 inches on each side of the door opening and 36 inches in front.
• At least 6 inches of air space between the anchor plate and flue and any combustible material.
• A non-combustible face on the enclosure, and the clearance spaces never packed with insulation.

Height Above the Roof

A factory-built chimney ends where its maker says. For masonry chimneys, section R1003.9 sets the familiar rule of 3 feet above the roof where it passes through and 2 feet above any part of a building within 10 feet, and one outdoor fireplace maker repeats that rule for its own termination cap, placed away from trees and structures. Under a pitched pavilion roof, that can mean a stack that rises above the nearest ridge.

A Fireplace in the Outdoor Kitchen

Outdoor kitchens often pair a fireplace with the cooking appliances, and the two are not interchangeable. One outdoor wood fireplace manual warns not to use its fireplace to cook or warm food. Built-in gas grills and ovens follow their own makers' instructions and the gas code, while a wood oven brings the chimney rules above. Each one gets its own flue.

How Oven Flues Are Swept

A wood oven's flue collects soot and creosote like any chimney; EPA notes creosote forms where smoke condenses in a cool flue, which a short oven stack does easily. The oven manual says the chimney and connector must be kept clean and in good condition, and the national standard, NFPA 211, calls for every chimney to be inspected once a year. On a factory-built chimney the cap comes off for cleaning, as one outdoor fireplace manual shows, so the pipe can be brushed from the top.

An oven flue through a roof is roof work, and a fall from a pavilion is as serious as one from a house. Our chimney sweep visit covers oven flues, and new outdoor kitchen chimneys are outdoor fireplace installation work. Expect a free inspection and a written estimate from a locally owned family business and its experienced crew. We are Proudly American, and we check clearances before any pizza is baked, which is how a Proudly American crew starts any kitchen job.