M&G DuraVent DuraPlus® - Manual (Page 9)

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through a Firestop Radiation Shield, a ceiling,
and into an attic. The other is a multi-story
building where the chimney passes through a
Firestop Radiation Shield, through a ceiling,
into another story, and then into an attic.
Each of these require a different configuration
of the Firestop Radiation Shield. Figure 7
dimensions as specified in Table 2. If Elbows
must be used to avoid an obstruction, refer to
the offset elbow installation section.
5. Cut Roof Opening: Cut an opening in the
roof directly above the opening below, and
at least 4 inches larger than the chimney’s
outside diameter to provide at least a 2-inch
clearance all around the chimney. If the
installation is located between rafters that
are 16 inches on center, Close Clearance
Shields (a sheet metal product fabricated by
DuraVent), may be used to avoid structural
reframing. (Figure 8). The 2-inch minimum
clearance to combustibles is not required when
the chimney passes through Close Clearance
Shields. When using Close Clearance Shields,
Ventilated Flashing must be installed. Refer to
Figure 10, which pictures both Ventilated and
Non-ventilated Flashing.
6. Install Firestop Radiation Shield: One
of two possible situations exist for installing
the Firestop Radiation Shield. One is a
two- story dwelling where the chimney passes
TABLE 2
FRAMING FOR SqUARE SUPPORT BOxES, ROUND SUPPORT BOxES AND WALL THIMBLES
SQUARE SUPPORT BOXES
Chimney inside diameter
6 INCHES 7 INCHES 8 INCHES
Framed opening inside dimensions 14 ½ x 14 ½ 14 ½ x 14 ½ 14 ½ x 14 ½
ROUND SUPPORT BOXES
Chimney inside diameter
6 INCHES 7 INCHES 8 INCHES
Framed opening inside dimensions 14 ½ x 14 ½ 14 ½ x 14 ½ 14 ½ x 14 ½
WALL THIMBLES
Chimney inside diameter
6 INCHES 7 INCHES 8 INCHES
Framed opening inside dimensions 14 ½ x 14 ½ 14 ½ x 14 ½ 14 ½ x 14 ½
FIRESTOP RADIATION SHIELD
Chimney inside diameter
6 INCHES 7 INCHES 8 INCHES
Framed opening inside dimensions 14 ½ x 14 ½ 14 ½ x 14 ½ 14 ½ x 14 ½
Figure 8
14 INCHES 14 INCHES
14 INCHES
x
x
CUT PANEL’S TO
ROOF PITCH LINE
ROOF
PITCH
LINE