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PLUMBLINE
PLUMBLINE
MEASURE
TRAVEL
DISTANCE
OVERHEAD
OBSTRUCTION
TRAVEL
DISTANCE
43
DM Chimney System: Offset Block (cont.)
Offset block Support Foundations:
It is required that every third Isokern offset chimney
block in the sequence be supported down to footings via concrete
block or steel support columns.
Plan fireplace and DM chimney systems carefully
before foundations are laid to assure that proper footings are
available to support Isokern offset blocks chimney run.
To calculate the distance of Isokern offset chimney
travel in a straight line to the right, left or to the rear of the
firebox/smoke dome assembly, proceed as follows:
Refer to Figure 89: temporarily dry set a DM outer
casing block in its proper location on top of the completed
firebox/smoke dome assembly as though starting a straight
chimney.
If the offset sequence is to move to the left then, starting
from the right side of the temporary DM outer casing measure
left ward to the far face of the overhead obstruction that needs to
be bypassed by the vertical chimney run.
For accurate measuring drop a plumb line down from
the far face of overhead obstruction to the level of the top of
the smoke dome assembly. Measure from the far side of the
temporary DM outer casing to the plumb line. This measurement,
taken in inches and divided by three (three inches of horizontal
travel per offset block) gives the total number of offset blocks
needed to accomplish the required travel distance.
To calculate the height that the offset block sequence
will require, take the total number of offset blocks needed to
accomplish the travel distance (described above) multiplied by
6”. This number is the height (inches) that the offset sequence
will require.
When establishing the “far face” of the overhead
obstruction, be sure that the DM chimney blocks can run straight
to chimney termination without further overhead obstruction
since a second offset sequence is not allowed. (Figure 90)
Be sure that there is sufficient space beyond the “far
face” of the overhead obstruction to accept the DM chimney’s
outer casing dimension of 21 1/2”.
Support all offset sequences down to bearing as
previously discussed on page 40.
Note:
Always support the last offset block in a sequence for
full support of the DM chimney where it returns to vertical.
Support columns often carry the majority of the total
load of the vertical chimney that is set onto the last offset block.
The total chimney weight above the last offset block
will be the total weight of the vertical chimney plus any additional
allowable loads such as the Isokern brickledge, its related brick
or stone veneers, and any crown caps, clay pots or other masonry
chimney terminations.
Be sure the foundation under all support columns
is made of concrete or steel and designed to support the loads
applied to it.
FIGURE 90
FIGURE 89
NOTE Cont:
Check with local codes and a structural engineer to
confirm loading and foundation requirements.
Chimney runs are limited to one offset sequence per
chimney system.
Maximum horizontal distance of offset is six feet
(6’) and represents twenty-four offset blocks in sequence.
By code the maximum angle of offset for chimney
system is 30° off of vertical.
Summary of Contents for Magnum 86072-60
Page 2: ......
Page 40: ...40 DM Chimney System Lateral Support cont FIGURE 81 FIGURE 82 ...
Page 55: ...55 Notes ...