M&G DuraVent DuraTech® 5-8 - Manual (Page 8)

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Support, refer to the Square ceiling installation
below. The Round Ceiling Support Box has
the option of a square or round Trim Collar
available (Fig 5). The bottom of the Round
Support Box must extend at least 3 inches
below the finished ceiling. Level the Support
Box and secure it to the framing using at least
three 8-penny nails per side (min. of 12 total).
Alternatively, you may use 1-1/2” #8 wood
screws (min. of 12 total), instead of nails.
Next, secure the Trim Collar (round or square)
to the framing members using the (4) 1” long,
round-head wood screws provided (Fig 6).
For installation into a cathedral ceiling, you
must use the Square Ceiling Support Box or
Reduced Clearance Support Box (or the CAS
Ceiling Support if installing the CAS system)
and the two-piece Trim. The bottom of the
square portion of the Support Box must be a
minimum of 2-inches lower (round portion is
an additional 3 inches lower) than the finished
ceiling at the lowest side of the penetration
(Fig 5 & 6). Level the Support Box and
secure it to the framing using at least three (3)
8-penny nails per side (minimum of 12 nails
total), or a minimum of (3) #8, 1-1/2” wood
screws. Adjust the overlapping “U-shaped”
Trim pieces so they cover the Support Box,
and secure them to the framing members
using the (6) 1-1/4” long, round head wood
screws provided (see Fig 6).
4. Frame Openings: Frame openings in
each ceiling or floor above the Support Box
(Fig 7). These openings are to hold the
Firestop Radiation Shield and Attic Insulation
Shield. Locate each opening by dropping a
plumb bob to the four corners of the opening
below. Maintain the framing dimensions as
specified in Table 2.
Warning: other than the framing for the
Reduced Clearance Support Box, any
combustible materials around the chimney
must still meet the minimum 2” clearance
requirement. 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.
The chimney must be centered within this
Figure 6
Figure 7
MIN OF 2
INCHES
BELOW
FINISHED
CEILING
WOOD SCREWS ARE
REQUIRED
WOOD SCREWS ARE
REQUIRED
ROUND CEILING
SUPPORT WITH TRIM
IN PLACE
SQUARE CEILING
SUPPORT BOX WITH
TRIM FRAME
IN PLACE
CAP ADJUSTABLE
FLASHING
CHIMNEY
SECTION
ATTIC
INSULATION
SHIELD
STORM
COLLAR
FIRESTOP
RADIATION
SHIELD
CHIMNEY
SECTION
FRAMED
ENCLOSURE
2 INCH MIN
CLEARANCE
TO INSIDE OF
ENCLOSURE
MIN OF 3
INCHES BELOW
FINISHEDCEILING
18 INCH MIN FOR
SINGLE WALL
STOVEPIPE