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Fireplace flues, chimneys and vent
connectors should be inspected carefully, as they impact the safety,
health, welfare and comfort of the occupants.
Every fireplace must have a separate
flue. Fossil fuel-burning appliances should have separate flues.
There are exceptions. Multiple appliances are allowed to use the
same flue as long as the vent connector and the chimney flue can handle
the volume of exhaust from the appliances. The most common
situation where this occurs is when a heating appliance and a water
heater use the same flue. The vent connector from the water heater
or appliance with the smaller burner should enter the chimney flue above
the heating appliance or appliance with the larger burner.
 Modern
construction requires liners in all masonry chimneys. However, there
are thousands of older homes that do not have lined chimneys.
Generally speaking, these chimneys have 8² or thicker walls, and if there
is not an excessive amount of deterioration, are satisfactory. The
fact that all modern chimneys require linings is one of the reasons that
chimney specialists nearly always propose new linings, whether they are
needed or not. The older the chimney, the more likely it may need a
liner.
Determining the condition of a chimney
requires a thorough understanding of the functions of the chimney and
items that may impact its condition and functionality. Items that
impact condition include:
-
Temperature of the flue gases
-
Quality and condition of the
brick
-
Quality and condition of the
mortar, inside and outside of the chimney
-
Workmanship – such as mortar
mix; the way it is connected to the masonry or frame structure;
depth and design of the foundation; and the skill level of the mason
-
Length of the vent connector
(heating system)
Items that impact functionality
include:
-
Workmanship – such as throat
and smoke-shelf; ratio sizes of the flue and
firebox opening; depth of the firebox;
and damper installation
-
Location of the chimney, as it
relates to wind currents
-
Design of the firebox, throat and
smoke chamber, etc.
-
Height of the chimney
Masonry chimneys in modern
construction are normally lined with terra cotta liners. These liners
are dependable for 50 or more years, unless condensation forms in the
chimney when the attached appliances are operating.
Brick, solid block or concrete that
is 4² thick requires a fireclay liner. These liners are sized for the
fireplace or appliance they service and should be 5/8² thick.
Stone chimney walls should be at
least 12² thick. Liners are required in modern construction,
however, they were not required in older homes.
Chimneys that are only one brick
thick, without a liner, can be considered a fire hazard. Chimneys
that are 8² or 2 bricks thick, without a flue, are acceptable as long
as the mortar is in good condition.
Brick
Problems in Chimneys
Cutting or chiseling the problem bricks
out and replacing them can repair these conditions. Cost may be
$30.00 to $40.00 per brick with a $300.00 minimum. Placing cement
stucco over the problem bricks is an option, however, this would not be
recommended unless the appearance was not a concern.
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Backdrafting Vent
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