Required chimney height above apex of roof??

poochie2009

guys,since the last post i put out worked well today,heres another one.
Is there a required height for the top of the chimney to be above the heights point of the roof?i hear it has to be so downdraft doesnt occur! my chimney is 150mm above the top of the roof and is 2 meters away!any thoughts?

sydthebeat

http://www.environ.ie/en/Publications/DevelopmentandHousing/BuildingStandards/FileDownLoad,1639,en.pdf

see part 4.

poochie2009

syd,
i had a look at that and im in zone b but that doesnt tell me the minimum height that a chimney can be above the roof...or maybe im interpretating the document different?

sydthebeat

i beg your pardon, i read your post incorrectly.

basically there are two things you need to consider, ventilation to draw teh smoke, and structure of the chimney element.

the TDG that i linked to deals with the structural element.

Typically, the top of the chimney pot needs to be a minimum of 600mm above the ridge line to create adequate draw.
There is scope to lower this depending on distance from the ridge....
Refer to Diagram 1 here:
http://www.environ.ie/en/Publications/DevelopmentandHousing/BuildingStandards/FileDownLoad,1650,en.pdf

Penn

Going by the HomeBond manual:

If the side of the chimney is less than 600mm from the ridge, the chimney must be 600mm above the ridge

If the chimney is 600mm or more from the ridge, the chimney must be minimum of 1m above the highest point where the roof meets the chimney

poochie2009

thanks guys, from all that info,my chimney is ok!!