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Masonry Chimneys
The minimum requirements for a properly constructed
chimney include the following:
• The foundation must be large enough to support the
intended chimney without settling.
• The masonry wall of the chimney, if brick or modular
block, must be a minimum of 4" nominal thickness. A
mountain- or rubble-stone wall must be at least 12"
thick.
• The chimney must have a fireclay flue liner (or
equivalent with a minimum thickness of 5/8" and must
be installed with refractory mortar. There must be at1/
2" air space between the flue liner and chimney wall.
• The preferred fireclay flue liner size has a nominal
size of 8" x 8", and should not be larger than 8" x12". lf
round fireclay liners are used, the inside diameter
should be 6" and not larger than 8". lf an existing
chimney with larger tiles is used it should be relined
with an appropriate liner.
• No other appliance can be vented into the same flue.
• An airtight cleanout door should be located at the base
of the chimney.
A chimney inside the house must have at least 2" of
clearance to the combustible structure. A chimney outside
the house must have at least 1" clearance to the
combustible structure. Fire stops must be installed at the
spaces where the chimney passes through floors and/or
ceilings. Remember that there must be air space around
the chimney, and that insulation must be 2" or more from
the chimney.
A chimney, wether masonry or prefabricated metal, must
be the required height above the roof or other obstruction
for safety and for proper draft operation. The requirement
is that the chimney must at least 3' higher than the highest
point where it passes through the roof and at least 2'
higher than the be at least and highest part of the roof or
structure that is within 10' of the chimney, measured
horizontally (fig. 4, page 21).
Chimneys shorter than 14' may not provide adequate draft.
This could result in smoke spilling the room from the door
or joints in the stove or pipe. In addition, inadequate draft
can cause puffing. A too-strong draft, on the other hand,
cause excessive temperatures and can shorten burn
times. Excessive drafts can be corrected by having your
dealer install a barometric damper at 0.1 " of water
column. lf you suspect you have draft problem, consult
your dealer.
Listed Metal Prefabricated Chimneys
The heater must be connected to a listed Type HT per
UL 103 or ULC S629 prefabricated chimney. When a metal
prefabricated chimney is used, the manufacturer's
installation instructions must be followed precisely. You
must also purchase (from the same manufacturer) and
install the ceiling support package or wall pass through,
the "T" section package, the firestops (when needed), the
insulation shield, the roof flashing, the chimney cap, etc.
Maintain the proper clearance to the structure as
recommended by the manufacturer. This clearance is
usually a minimum of 2", although it may vary by
manufacturer or for certain components.
There are basically two methods of metal chimney
installation. One method is to install the chimney inside
the residence through the ceiling and the roof (fig. 5,
page 22).
The other method is to install an exterior chimney that
runs up the outside of the residence.
C. Connection to the Chimney
Masonry Chimneys
When connecting to a masonry chimney, the chimney
connector must slide completely inside the chimney
thimble (or breach) to the inner surface of flue liner, make
sure the connector does not protrude past the inside of
the flue liner as that will reduce the flow area available
for the smoke and ultimately cause problems with your
chimney system. The chimney connector should be sealed
into the thimble with refractory cement and the connector
should also be mechanically fastened to the chimney.
See fig. 6, page 22.
Prefabricated Chimneys
Always follow the chimney manufacturer's instructions
and use all the components required by the manufacturer.
Do not take shortcuts or use make shift methods for
securing the chimney connector to the chimney.
Note: The clearances expressed in inches are those
approved for installations in the United States. The
clearances in parentheses that are expressed in
centimeters are those approved for installations in Canada.
Different test standards for the respective countries may
result in differences in the clearance requirements.
USA