How high does the chimney/flue need to be?

Posted on Tuesday 8th November 2011 @ 7:50am NZDT by

How high does the chimney/flue need to be?

No matter which type of flue system is used, the height is critical to achieve the correct draught (see figures below). If a flue system is built and installed to the proper height, it will normally prevent down draught problems during windy weather and eliminate smoke spillage problems due to lack of draught.

The following figures from AS/NZS2918:2001 specify the following requirements:

  • If the centre of the flue passes through the roof within 3.0 metres of the ridgeline, the flue height must not be less than O.6 metre above the ridgeline.
  • If the centre of the flue passes through the roof further than 3.0 metres away from the ridgeline, then the flue height must be a minimum of 1.0 metre above the roof, or until above a height measured 3.0 metres horizontally back to the roof slope.
  • If the centre of the flue passes through the roof within 3.0 metres of another nearby structure (or part of), then the flue height must be extended until above a height measured 3.0 metres horizontally back to the nearby structure roof slope.

AS/NZS 2918:2001

AS/NZS 2918:2001 – FIGURE 4.9 MINIMUM HEIGHT OF FLUE SYSTEM EXIT


About Ian

I am a New Zealand and EC citizen, living and working in Hastings in the North Island of New Zealand. On March 5th in 2004 I retired from exactly 30 years with IBM UK Ltd, working in the Hursley software development lab near Winchester in the south of England. I am now an IBM Distinguished Engineer emeritus, working to my own agenda while retaining access to my colleagues and information inside IBM.
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