DIY Metal Flue Install

A fireplace can use a metal flue to allow the smoke to escape the house.

A metal flue provides a safe path for the combustion produced from furnaces, water heaters, and fireplaces to make it outside the building. These flues are typically double-walled metal pipes with an air space in the middle. The air space provides the insulation from the direct heat of the exhaust gases. Installing the flue properly is vital to avoid starting a building fire or releasing toxic gases into the living environment.

Things You'll Need

• Measuring tape
• Miter saw
• Framing lumber
• Drill
• Wood screws
• Metal self-tapping screws
• Draft hood connector
• Metal vent
• Wall supporting straps
• Flashing cone
• Storm collar
• Sealant
• Metal flue cap

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Instructions

1. Contact your local building authority to apply for a permit for the installation of a flue, and also to learn about the local rules for such a project.

2. Plan a path for the chimney to take. Common chimney rules state that the flue can make no more than a total of 90 degrees of turns (typically two 45-degree corners) and should extend 2 feet above any object within a 8 foot radius of its penetration point. If the flue runs horizontal at any location, it must slope upwards at 1/4 inch per foot.

3. Mark the center of the penetration points in the wall's or ceilings. Frame this area with a wood square to the dimensions listed in the resource section. The diameter of the flue determines the size of the square. Install the wall thimble between the framing members by securing it to the wood framing with nails through the marked holes.

4. Connect the draft hood connector to the top of the appliance by inserting it into its exhaust exit. Secure with three self taping screws and a drill. All connections need to be tight enough to prevent any air gaps.

5. Hold the next section of metal flue above the draft hood connector and insert into it. Once the two pipes are connected, turn the top metal pipe clockwise to lock them together. Repeat this step to connect the various sections of flue pipe to make the entire run.

6. Install wall supporting straps to the framing of the wall system, and wrap them around the metal flue to provide ample support. At minimum there should be two supporting straps installed on either side of each corner.

7. Pull the flashing cone over the top of the metal flue above the roof, then slide the storm collar on next. Apply a bead of sealant around the inside edge of the storm collar to prevent water penetration into the building.

8. Insert the metal flue cap over the last section of pipe, and secure with three self-tapping screws.

9. Contact your local building authority to set up an inspection for the new installation, to assure that it is safe and fully meets the local building codes.

References

• Chemeketa International Code Council: B-Vent Installation