On Sep 13, 7:07*pm, "Sheldon" wrote:
Thanks
"DerbyDad03" wrote in message
...
Sheldon wrote:
I cannot find anything on the web that indicates that the flue has to
extend 2" beyond the crown.
The chimney has to be 3' beyond the portion of the roof where it emerges.
The chimney also has to be 2' higher than anything that is within 10'.
"DerbyDad03" wrote in message
...
wrote:
On Sep 13, 1:07 pm, DerbyDad03 wrote:
Sheldon wrote:
Why are so many chimneys built with the flue(so) that extend above
the
crown?
For Looks?
To improve the chimney draw? *I would think the small increase in
height
would make little or no difference
To allow the chimney to meet code? *I would think the chimney could
just
have been built at the correct height in the first place.
Sheldon
AFAIK, the code requirement in most areas is that the flue must extend
at least 2" above the crown. YMMV
Picture wind gliding across a sloped crown with no flue extension. You
can almost imagine the wind sort of sealing the flue opening.
Now picture wind gliding across a sloped crown and hitting the wall of
a
2" extension. The wind is forced upward instead of flowing across the
opening.- Hide quoted text -
- Show quoted text -
extension helps screw chimney cap on......... try to do it with "
flush flue"
But is that why it's code?
I found lot's of references to the flue being 2" above the crown but none
of them cite specific code references, other than "Check your local code".
This site says it the best, but I've included a few other references for
your reading pleasure.
ftp://imgs.ebuild.com/woc/M930413.pdf
Make sure the flue liner extends at least 2 inches beyond the top of the
chimney, but check local building codes for the requirements in your area.
This extension permits attachment of a rain hood and keeps ice and snow
that accumulates on the crown from dropping into the flue. To avoid
excessive cooling and condensation, don’t project the flue liner more than
6 inches above the crown.
http://www.chimneylinerdepot.com/lan...ey-anatomy.asp
Most flue liners extend above the chimney crown at least two inches. In
some chimneys the liner may extend higher than this depending on local
building codes.
http://www.diychatroom.com/showthread.php?t=3970
The crown should slope away from the flue liner, the flue liner should
protrude at least 4" from the crown and the joint between the flue liner
and the cap should be sealed with a flexible joint sealer.- Hide quoted text -
- Show quoted text -
In our area it must extend 4inches or more 6 is the norm