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collar to the pipe at the appropriate place.
Apply silicone sealant over the sheet metal
screw head. Gas vents supported only by
the flashing must be guyed above the roof
to withstand snow and wind loads. All gas
vents extending above the roof more than 5
feet must be securely guyed or braced.
When offsets are necessary, adequate
support above and below the offset is
required. In addition, securing the offset
elbow with three maximum 1/4" long sheet
metal screws is recommended.
13. FLASHING
The roof opening should be located and
sized such that the vent is vertical and has
the required air space clearance. The Tall
Cone Flashing is for flat roofs only (see Fig.
14). It is nailed in place through all four
sides of the base flange. The Adjustable
Roof Flashing (see Fig. 15) is positioned
with the lower portion of the base flange over
roofing material and the upper portion of the
base flange under the roofing material. Nail
through only the upper portion and sides of
the base flange. (DO NOT nail through lower
flange.) Use nails with a neoprene washer, or
cover the nail heads with a silicone sealant.
Finish roofing around the flashing, covering
the sides and upper areas of the flange with
roofing material. A non-hardening sealant
may be used around the edges of the flashing
base where it meets the roof.
FIG. 14
Tall Cone Flashing For
Flat Roofs Only
Storm Collar
Top and Sides
of Flashing
under Roofing
Maintain
minimum
25mm (1") clearance
to combustible and
BV Type B Gas Vent
FIG. 15 - Flashing Installation
Apply a Non-
Hardening
Silicone Sealant
Flashing
Bottom of
Flashing over
Roofing
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
14. VENT TERMINATION
Gas vent piping must extend through
the flashing to a height above the roof
determined by Rule 1 or Rule 2 shown below.
A storm collar is installed on the vent pipe
over the opening between pipe and flashing.
A non-hardening silicone sealant is used over
the joint between pipe and storm collar. The
top is securely attached to the gas vent as
per section 15.
Rule I: For Pipes 12" and Under
The top is suitable for installation on listed
gas vents terminating a sufficient distance
from the roof so that no discharge opening
is less than 2 feet horizontally from the roof
surface, and the lowest discharge opening
will be no closer than the minimum height
specified in Fig. 16-B. These minimum
heights may be used provided that the vent
is not less than 8 feet from any vertical wall.
Rule II - Tops for gas vent sizes 14" and larger
or less than 8' from vertical wall.
For installations other than covered by the
Table 1 (Fig. 16-B), or closer than 8 feet
to any vertical wall, the DuraCap shall be
not less than 2 feet above the highest point
where the vent passes through the roof and
at least 2 feet higher than any portion of a
building within 10 feet. DuraCap 14" and
larger must comply with Rule II regardless
of roof pitch.
These rules were established on the basis
of tests conducted in accordance with
American National Standard ANSI/UL 441
and ULC-S605.
12" Minimum
distance
to roof
FIG. 16A - Roof Pitch 7/12 or Less
DuraCap
Cap
Non-Hardening
Silicone Sealant
Storm Collar
Flashing
13
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