The figures above are minimum clearances for typical domestic boilers.
Boiler flue height above roof.
300 mm above ground roof or balcony level 2000 mm below a velux window for a vertical flue 300 mm above roof pitch or flat roof for a vertical flue note that more powerful boilers might require larger clearances between the flue and the relevant object.
From my very limited understanding of building regs part j for where the flue should be positioned i thought that the height of the top of the flue must be a minimum of 2 feet above the ridge.
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.
Homes built on varying terrain have their own set of chimney and flue regulations.
If your boiler flue has to face out onto a public space the installer will have to ensure that it s fitted at least 2 1 metres above ground level over head height.
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.
The amount of flue protruding from the slope of the roof is about 2 feet but the top of the flue is just a bit higher than the ridge of the roof.
Alternatively if your flue exits within section b then your vertical distance remains at least 1800mm and at least 2300mm horizontally from the roof surface.
So take the top number of your roof pitch and multiply it by 10 then add 24 note example 1.
Additionally per our rule we need to add 2 feet or 24 inches giving us a total height of 64 inches.
Flues need to be 600mm higher than the highest part of the roof within 3 metres.
Roof pitch rise run in inchesminimum height flat to 7 12 1 0 foot above the roof surface 7 12 to 8 12 1 5 feet above the roof surface 8 12 to 9 12 2 0 feet above the roof surface.
Flues that are more than 3 metres away from the highest part of the roof need to be 1000mm above the flue penetration.
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.
Back to our example over a run of 10 feet the roof would rise 40 inches.
Degrees the height of flue or chimney stack will need to be at least 1800mm above the roof when not close to the ridge.
Vent caps 12 and smaller may terminate a distance above the roof if 8 feet or more away from a vertical surface as follows.
