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ADJUSTABLE FIRESTOP THIMBLE (FST-A):
The Adjustable Firestop Thimble Assembly (FST-A) is used
to provide the necessary air space and clearance between the
chimney pipe and the insulation in the attic space of a
manufactured home.
To install the thimble assembly, determine the distance
between the ceiling joist and the roof framing. Attach the
adjustable thimble to the firestop spacer so that the assembly
will cover the distance. The adjustable thimble should be even
with or above the roofline (see thimble extensions on page 11
if a longer thimble is needed). Sheet metal screws or staples
may be used to attach the thimble to the firestop spacer.
An opening large enough to allow the insertion of the firestop
thimble assembly will be required in the ceiling. Attach the
firestop/thimble assembly to the ceiling/ceiling joists using
screws or staples as shown in figure 9a. A minimum of 8
screws or staples should be used.
Figure 9a
The firestop thimble assembly should also be used where there
is a cathedral ceiling, insulation barrier and roof, all in one
assembly in a manufactured home (see figures 9b & 10). The
FST-A Thimble can be used in any one of three common
ceiling pitches; flat, 12"/96", and 30"/144".
An opening big enough to allow the insertion of the firestop
thimble assembly will be required. This opening depends on
the pitch of your ceiling. If your ceiling is a flat or 12"/96"
pitch, you must use the adapter plate provided to seal
unwanted openings since the opening in the firestop is an
ellipse. For 30"/144" pitch, discard the adapter.
Figure 10
Figure 9b
If the adapter is needed, secure it onto the firestop using holes
provided (see figure 10). The row of holes on the sides of the
thimble is provided to allow for pitch variances. Position the
firestop assembly and thimble to desired angle and secure with
screws provided.
Insert the thimble and firestop into the
prepared opening and secure to the ceiling by nailing through
the firestop flanges. The thimble should be even with or
above the roofline. Thimble extensions are available (as an
option) when required. See "accessories" on page 11.
NOTE: If there is a second story in the home, firestop
spacer 3600FS-8DM will be required.
Spacer" on page 9.
PENETRATING THE ROOF:
To maintain a 1-inch clearance to the pipe on a roof with a
pitch, a rectangular opening must be cut.
STEP 1: Determine the center point through which the pipe
will penetrate the roof.
STEP 2: Determine the center point of the roof. Pitch is the
distance the floor drops over a given span, usually 12 inches.
A 6/12 pitch means that the roof drops 6 inches for each 12
inches measured horizontally down the roof.
STEP 3: Use the roof-opening chart (figure 11) below to
determine the correct opening length and flashing required.
STEP 4: Remove the shingles around the opening measured
and cut out this section.
STEP 5: Add the next sections of the pipe until the end
penetrates the roofline.
clearances are maintained. Extend chimney by adding sections
of double wall pipe until pipe is a minimum of 30 inches
above the highest point of the roof cutout. Termination and
chimney must extend a minimum of 36 inches above the
highest point where it passes through roof.
PITCH
(degrees)
FLAT
0 - 6/12
6/12 - 12/12
Figure 11
IMPORTANT: If an exposed portion of chimney is greater
than four feet above the roofline, use support wires to keep the
chimney secured. The support wires may be attached to the
outer pipe of the chimney with screws provided the screws do
not penetrate the inner flue pipe.
5
See "Firestop
Check to see that the proper
SLOPE
OPENING "A" MAX
USE FLASHING
(inches)
MODEL NO.
0
15
26.6
16 - 1/8
45.0
20 - 3/8
6F-8
6F-8
12F-8
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