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A short, masonry chimney on the exterior of a house will
promote poor performance. This is because it will be difficult
to initiate and maintain temperatures warm enough to sustain
adequate draft. In extremely cold northern areas, it may be
necessary to reline the chimney or extend its height to help
improve performance. Conversely, a tall, masonry chimney
inside the house will warm more quickly and retain heat longer.
On the other hand, overly strong draft can also cause a different
set of issues such as excessive temperatures and short burn times
Ideally, whether masonry or prefabricated, the chimney should
be centrally located inside the house where it will be least af-
fected by exterior conditions and the stove's radiant heat can be
most evenly dispersed.
The following guidelines give the necessary chimney
requirements based on the national code, ANSI-NFPA 211.
However, many local codes differ from the national code to
take into account climate, altitude, or other factors.
NOTE:
Consult your local code authority to determine
what building and fire codes apply in your area before
installing your new stove.
authority in approving your installation.
2.3 Masonry Chimneys
A masonry chimney must conform to the following guidelines:
• The chimney flue size should not be less than the cross-
sectional area of the stove flue collar.
• The cross-sectional area of the flue of a chimney with no
walls exposed to the outside below the roofline shall not be
more than three times the cross-sectional area of the stove
flue collar.
• The cross-sectional area of a chimney flue having one or
more walls exposed to the outside below the roofline shall
not be more than two times the cross-sectional area of the
stove flue collar.
• Larger chimney flues should be relined with a listed or code
approved liner.
• The masonry chimney must have a fireclay liner or
equivalent, with a minimum thickness of 5/8" (16mm) and
must be installed with refractory mortar. There must be at
least 1/4" (6,35mm) air space between the flue liner and
chimney wall.
• The fireclay flue liner must have a nominal size of 8" X
8", and should not be larger than 8" X 12". If a round
fireclay liner is to be used it must have a minimum inside
diameter of 6" (157mm) and not larger than 8" (208mm)
in diameter.
• If a chimney with larger dimensions is to be used, it should
be relined with an appropriate liner that is code approved.
Your local inspector has final
• The masonry wall of the chimney, if brick or modular block,
must be a minimum of 4"(106mm) nominal thickness. A
mountain or rubble stone wall must be at least 12" (310mm)
thick.
• A newly-built chimney must conform to local codes and in
their absence must recognize national regulations. W h e n
using an existing chimney, it must be inspected by a licensed
professional chimney sweep, fire official, or code officer, to
ensure that the chimney is in proper working order.
• No other appliance can be vented into the same flue.
• An airtight clean-out door should be located at the base of
the chimney.
2.4 Prefabricated Chimneys
A prefabricated metal chimney must be tested and listed for
use with solid fuel burning appliances to High Temperature
(HT) Chimney Standard UL 103 for the U.S.
The manufacturer's installation instructions must be
followed precisely. Always maintain the proper clearance to
combustibles as established by the pipe manufacturer. This
clearance is usually a minimum of 2" (56mm), although it may
vary by manufacturer or for certain chimney components.
2.5 Chimney Height
The minimum chimney height is 15 feet (4.57 m). The
chimney must also be at least 3 feet higher than the highest
point where it passes through the roof and at least 2 feet
higher than the highest part of the roof or structure that is
within 10 feet of the chimney, measured horizontally. See
figure 3.
Chimneys shorter than 14 feet may not provide adequate
draft. This could result in smoke spilling into the room from
the stove when loading the stove, or when the door is open. In
addition, inadequate draft can cause back puffing, which is a
build up of gases inside the firebox.
Other times, chimney height can create excessive draft
which can cause high stove temperatures and short burn times.
Excessive drafts can be corrected by installing a butterfly
damper. If you suspect you have a draft problem, consult your
dealer.
139946_18 F 500 V3 Oslo
May 2022
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