NOTE: DIAGRAMS & ILLUSTRATIONS NOT TO SCALE.
11
FTF8 CHIMNEY COMPONENT
CALCULATIONS
The minimum installed height of the com-
pleted fireplace system is 12' 0". The maxi-
mum height is 40' 0" when the chimney is
exposed.
To determine the number of chimney sections
and chimney components required, follow
these steps:
1.
Determine total vertical height of the fireplace
installation. This dimension is the distance from
the surface the fireplace sets on to the point
where smoke exits from the termination.
2.
Determine the number of chimney compo-
nents required, except chimney sections. This
would include thimbles, extensions, roof
flashing, etc.
3.
The effective heights of the components are:
The Fireplace
=
42
¹⁄₄
"
FTF8-12
=
10
¹⁄₄
"
FTF8-18
=
16
¹⁄₄
"
FTF8-36
=
34
¹⁄₄
"
FTF8-48
=
46
¹⁄₄
"
FTF8-BTM Termination
=
6"
4.
Determine amount of chimney height re-
quired by subtracting total combined height of
all pre-selected components (fireplace and
chimney components from total desired
height.)
Reference Vertical Elevation Chart and deter-
mine the number of chimney sections (quan-
tity and length) required.
SPECIAL OFFSET INSTRUCTIONS
Chimney 30
°
Offset through Floor or Ceiling
It may be necessary to assemble the chimney at
30
°
when passing through the floor or ceiling
area. Use the F8FS30-2 firestop spacer as shown
in
Figure 32. Support the chimney at floor or
ceiling penetration with a FTF8 stabilizer if
distance of chimney below ceiling is 10' or
more. Maintain 1" minimum air space to com-
bustibles from chimney sections. The chimney
must pass vertically through the attic space.
To clear any overhead obstructions, you may
offset your chimney system using FireCraft
30
°
offset and return elbows. Use two elbows
- an offset elbow to initiate the offset and a
return elbow to terminate it. A 30
°
offset
elbow, angling in any direction, may be the
first component used off the top of the fire-
place flue collar.
The offset and return elbows may be attached
together, or a section or sections of chimney
may be used between, but do not exceed 20' in
total length between elbows. If sections of
pipe exceed 10' between elbows, a chimney
stabilizer must be used at the midpoint (
see
Figure 33 ). The stabilizer support straps must
be attached under tension (in shear) to struc-
tural framing members above. When two sets
of elbows are used, the maximum combined
length of chimney used between elbows can-
not exceed 20' (
see Figure 34 ).
Example:
If C
1
= 10' then C
2
cannot exceed 10'.
If an offset exceeds 6' in length, each chimney
joint beyond the first 6' of offset to the return
elbow, must be secured by a No. 8 x
¹⁄₂
" sheet
metal screw located at the underside of the
joint (
see Figure 36 ).
A
¹⁄₈
" diameter hole must be drilled in the
chimney joint using a
¹⁄₈
" diameter drill. Hole
should be drilled in center of joint overlap (
see
Figure 36 ). Be sure to drill only through the
outer chimney casting. Do not puncture the
inner flue.
Figure 32
Maximum offset of chimney system is 30
°
.
Two offsets must not be assembled to form a
60
°
offset. However, two sets of offset and
return elbows may be used on a single flue
system, provided the total height of the sys-
tem exceeds 25'.
Return elbow support straps must be securely
attached under tension (in shear) to structural
framing members above. Do not substitute a
FTF8-30 offset elbow in place of a FTF8-E30
return elbow.
OFFSET CALCULATIONS
Step 1.
Use Offset Chart to determine amount
of horizontal offset (A) and height (B) for
various chimney section assemblies.
Step 2.
Use “Height of Chimney Only” column
in The Vertical Elevation Chart to determine
combinations of chimney used above return
elbow to achieve desired heights. Reference
Components Effective Height Chart in vertical
elevation chart section.
Step 3.
Use Elevation Chart as job estimator
only. Add necessary firestop spacers and sta-
bilizers as required. Firestop spacers must be
used as shown in
Figure 19 and stabilizers as
shown in
Figure 26.
Figure 33
Stabilizer
A
1
20'
Max.
B
1
10' Max.
Offset
Elbow
Return
Elbow
F8FS30-2
Firestop Spacer
FTF8-S4 Stabilizer
30
°
Firestop
And Room Above
10'
Max.
Room Above
1" Min.
Air Space
1" Min.
Air Space
