Roof Duct Chimney: Components

The Components and Their Functions

1. Double-walled element: the insulated pipe that safely channels smoke gases upwards and keeps the outer wall cool.

2. Roof duct tile or lead flashing: seals the roof opening around the duct watertight.

3. Storm collar: seals the seam between the duct and the pipe, preventing water from running down the pipe inside.

4. Spacers or brackets: keep the duct straight and stable, maintaining the distance from the structure.

5. Fire-resistant duct: mandatory for wooden or combustible roofs, as it maintains a safe distance from flammable materials.

6. Chimney cap or draft-enhancing finish: protects the outlet from weather and promotes draft.

Checklist: Is Your Set Complete?

• Double-walled element in the correct diameter and length

• Matching roof duct tile for a sloped roof or an adhesive plate for a flat roof

• Storm collar present

• Brackets and spacers for stability

• Fire-resistant duct for a wooden roof

• Chimney cap or finish at the top

• Sufficient height above the roof surface or ridge

Review this checklist carefully before you start. A missing piece is often only noticed on the roof, halting work. Preparing the complete set and checking the diameter in advance ensures faster and safer work.

Why a Complete Set is Important

A roof duct only functions properly if the set is complete. Without the storm collar, water can seep down the pipe inside. Without a fire-resistant duct on a wooden roof, there's a real fire risk. And without the right brackets, the duct may sag or tilt over time. Each component has its role, forming a cohesive whole.

The diameter is the starting point of your set. All components, from the double-walled element to the tile and chimney cap, must match that size. Never mix parts from different systems or brands, as the connections won't be gas-tight.

The double-walled element is intentionally insulated. This insulation keeps the smoke gases warm for good draft and keeps the outer wall cool at the duct. This way, the distance to flammable materials remains safe, and the chance of condensation in the duct is minimized.

If you want a complete overview of all parts between the stove and the roof, our explanation on which components you need for a chimney will help. For the approach with a flat roof, read how to install a chimney through a flat roof.

Height, Outlet, and Fire-Safe Duct

The height of the outlet and the fire-safe duct are not optional extras but fixed requirements. The outlet must be high enough above the roof surface or ridge for good draft and safe exhaust of smoke gases. For a combustible roof, a fire-resistant duct is needed to maintain the distance from the wood.

A too low or incorrectly placed outlet results in poor draft and smoke nuisance. Smoke can back up or cause problems near roof windows and neighbors. Correct height usually solves this and is part of the basic components of your roof duct.

The specific requirements vary by region and municipality in Belgium and by municipality in the Netherlands. Always follow your appliance's manual and local regulations as binding sources, and coordinate with your insurer if necessary. For a sloped roof, find the procedure in our guide on installing a chimney through a sloped roof.

If you're unsure about the setup or sealing, our article roof duct for a chimney, here's how it works provides more background. If you prefer to have the duct installed, see how we approach installing a chimney through the roof.