Log Burner Flue Height Above Roof

As illustrated below if your flue exits through the roof within section a then you are required to rise at least 1800mm vertically above the roof surface and at least 600mm above the ridge.

Log burner flue height above roof. The picture below may illustrate it better than my words. If the flue exits the roof further down then it must extend high enough to acheive 2 3m of horizontal clearance. However to comply with the approved document j of the building regulations the flue still needs to rise a total height of at least 4 5m unless the appliance manufacturer specifies less. If the flue is over 3 m from the roof apex the flue top must be 1 000 mm minimum above the roof and at least 3 m horizontally from the roof surface.

This ensures correct operation of the burner limits back draughts and prevents flue gases impinging on the roof. Flue gases from the stove must be able to discharge freely without presenting a fire or health hazard whatever the wind conditions. When installing a new twinwall flue system if the flue exits the roof within 600mm horizontally from the ridge high point of the roof then the flue must extend a minimum of 600mm above the ridge. The distance between the cowl of the flue and the adjacent roof wall structure should be higher than 2 3 mtr.

This means that the flue outlet needs to be positioned sufficiently high above the roof surface and surrounding buildings to prevent it being affected by wind eddies or downdraughts. If the pitch of the roof is 38 degrees or greater the termination point of the flue or chimney will need to be 2300mm horizontally from the roof line and roofing material. For an enclosure simulating a chimney this raises the question of how high above. The flue termination is within 600mm horizontally of the ridge in which case the flue finish at least 600mm above the ridge.

Flue outlet height unsafe. The height of the chimney above the roof surface measured at the up slope side of the chimney from the roof surface to the chimney top should be at least three feet the green line in our photo. This is a bit of an odd measurement and chimney clearance case because the chimney side is actually about 8 away from the roof edge. The horizontal distance from the top of the flue pipe to the roof should be at least 2300mm or it should finish above the ridge unless.

Should your roof be thatched or made of any other combustible material then as you can imagine these distances must increase.