Two things determine chimney draft.
How high chimney above roof line.
Degrees the height of flue or chimney stack will need to be at least 1800mm above the roof when not close to the ridge.
Specifications aren t there to merely cause you problems.
Homes built on varying terrain have their own set of chimney and flue regulations.
The 10 foot rule explains the clearance you need.
The chimney opening above the roof of a sticks and bricks house should be 3 feet above the roof line or 2 feet above any part of the building within 10 whichever is higher.
This means that below 38 degree roof pitches that the height of the flue outlet should be at least 1800mm above the roof when not close to the ridge and above 38 degree roof pitches the flue outlet height should be 2300mm horizontally back to the roof flue height figures are given in the table above where the flue is not close to the ridge.
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.
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.
Flues that are more than 3 metres away from the highest part of the roof need to be 1000mm above the flue penetration.
And at least 2 higher than any portion of a building within 10.
The chimney must extend at least 3 above the highest point where it passes through a roof.
The top of a chimney pipe must extend at least 2 feet above the peak of the roof if the pipe is within 10 feet of the peak.
Taller chimneys make more draft but chimneys exposed to outside cold don t.
Both above the flat roof and 2 feet above the point at which a horizontal line from the chimney would touch the highest portion of the nearest roof.
If the pipe is farther than 10 feet from the roof.
They intend to make sure that the chimney draws properly and that a fire hazard does not occur.
For most small structures like small cabins and tiny homes the tallest part of the structure is within 10 of the chimney.
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.
Flues need to be 600mm higher than the highest part of the roof within 3 metres.
Other factors can influence the necessary height of the chimney such as house stack effect and high altitude.
