7
member that the hole is measured on the horizon-
tal, then projected to the roof. The hole may then
be larger, depending on the pitch of the roof. See
Figure 9.
Figure 10. Metal Chimney Construction
F. Frame the opening, making sure that the rec-
ommended minimum clearance to combustibles
by the chimney pipe manufacturer exist between
the roof and the chimney making sure that dis-
tance is maintained all the way around.
WARNING: DO NOT PACK REQUIRED
AIR SPACES WITH
INSULATION OR OTHER
MATERIALS.
G. A wood chase may be constructed around the
exposed chimney for aesthetic effect. Be sure the
minimum recommended clearances to combusti-
bles by the metal chimney pipe manufacturer are
maintained inside the chase.
4.3 Height of Chimney
Figure 11 illustrates the proper height of the chim-
ney top. Correct height depends on the chimney’s
location on the roof and distance from the peak of
the roof. Surrounding trees, other buildings and
hills may also be a consideration.
Figure 11. Chimney Height
If the chimney top is not high enough, unusual
downdrafts may occur, resulting in undesired
smoke. For a more thorough explanation of the
figure 11 illustration it is basically the 2/10 rule.
Once the center of your chimney is ten feet away
from the roof it should then be extended an addi-
tional two feet in height. This means the chimney
does not have to extend above the peak of the roof.
Once it is ten feet away and extended two feet the
height is sufficient but should never be shorter than
three feet from where it penetrates out of the top
side of the roof.
