9
D. If chimney exit opening does not already exist,
locate the point where the chimney will exit the roof
by plumbing down to the center of the chimney.
Drive a nail into the roof to mark the center.
E. Measure to all sides of the nail and mark the
required opening, and then cut a hole in the roof.
Remember that the hole is measured on the hori-
zontal, and then projected to the roof. The hole
may then be larger, depending on the pitch of the
roof. See Figure 22.
F. Frame the opening, ensuring that the recom-
mended minimum clearance to combustibles by the
chimney pipe manufacturer exists between the roof
and the chimney, ensuring that distance is main-
tained all the way around.
WARNING: DO NOT PACK REQUIRED AIR
SPACES WITH INSULATION
OR OTHER MATERIALS.
G. Continue to add pipe sections, extending the
chimney through the roof.
H. A wood chase may be constructed around the
exposed chimney for aesthetic effect. Ensure the
minimum recommended clearances to combustibles
specified by the metal chimney pipe manufacturer
are maintained inside the chase.
I. Install roof flashing appropriate to the roof
pitch, and any other pipe accessories, per the pipe
manufacturer’s instructions.
J. Install the appropriate chimney cap for the pipe
being used.
4.3 Height of Chimney
Figure 26 illustrates the proper height of the chimney
top. Correct height depends on the chimney’s loca-
tion on the roof and distance from the peak of the
roof. Surrounding trees, other buildings and hills
may also be a consideration.
If the chimney top is not high enough, unusual
downdrafts may occur, resulting in undesired smoke
spillage. For a more thorough explanation of the
Figure 25. Metal Chimney Construction
Figure 26. Chimney Height
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