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TEN FOOT RULE SUMMARY
The minimum chimney height above the roof
and/or to adjacent walls and buildings is speci-
fied by all major building codes.
If the horizontal distance from the peak of the
roof is less then 10', the top of the chimney
must be at least 2' above the peak of the roof.
If the horizontal distance from the chimney
edge to the peak of the roof is more than 10' a
chimney height reference point is established
on the roof surface 10' horizontally from the
chimney edge. The top of the chimney must be
at least 2' above this reference point. In all
cases, the chimney cannot be less then 3'
above the roof at the edge of the chimney.
The 2' in 10' rule is necessary in the interest of
safety but does not ensure smoke-free opera-
tion. Trees, buildings, adjoining roof lines,
adverse wind conditions, etc., may require a
taller chimney should the fireplace not draft
properly ( see Figure 32 ).
FTF8 CHIMNEY COMPONENT
CALCULATIONS
The minimum installed height of the BM36ST
fireplace system (including fireplace and chim-
ney components) is 15' (4.6 m). 25' (7.6m)
with two offsets. The maximum system height
is 80' (24.4 m).
To determine the number of chimney sections
and chimney components required, follow
these steps:
Less Than 10'
3'
Min
Figure 32
1. Determine total vertical height of the fire-
place installation. This dimension is measured
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 firestop spacers, stabilizers,
roof flashing, etc.
3. The effective heights of the components are:
BM36ST Fireplace
=
48" (1219 mm)
10 ¹⁄₄" (260 mm)
FTF8-12
=
16 ¹⁄₄" (413 mm)
FTF8-18
=
34 ¹⁄₄" (870 mm)
FTF8-36
=
46 ¹⁄₄" (1175 mm)
FTF8-48
=
CTD Termination
=
6" (152 mm)
S4 Stabilizer *
=
3" (76 mm)*
* Required for every 30' (9.1 m) of vertical
chimney and 10' of offset chimney.
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 (quantity
and length) required.
2' Min.
10'
NOTE: DIAGRAMS & ILLUSTRATIONS NOT TO SCALE.
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 33 .
Support the chimney at floor or ceiling pen-
etration with a FTF8 stabilizer if distance of
chimney below ceiling is 10' or more. Main-
tain 2" minimum air space to combustibles
from chimney sections. The chimney must
pass vertically through the attic space.
Room Above
F8FS30-2
Firestop Spacer
2" Min.
Air Space
Max.
Figure 33
A 30° offset elbow, angling in any direction,
may be the first component used off the top of
the fireplace 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 34 ).
The stabilizer support straps must be attached
under tension (in shear) to structural framing
members above. When two sets of elbows are
used, the maximum combined length of chim-
ney used between elbows cannot exceed 20'
( see Figure 35 ). Example: If C
cannot exceed 10'.
3'
Min
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 ).
2" Min.
Air Space
FTF8-S4 Stabilizer
30° Firestop
10'
And Room Above
= 10' then C
1
2
11
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