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DM Chimney System: Offset Block
DM Offset Chimney Block:
For vertical DM chimney to bypass overhead
obstructions, the Isokern offset chimney block is used.
Offset blocks are six inch (6”) thick, single module chimney
components, measuring twenty-one and one-half inch (21-1/2”)
wide by twenty-five inches (25”) long. The fourteen inch hole
passes through the block at thirty (30°) degrees.
An offset chimney block can be set as the first flue component on
top of the Magnum 86072 smoke dome.
When building offset sequences it is necessary to
support the third offset block in the sequence and every third
offset block thereafter. When using only one or two offset blocks
no additional support is required.
Offset sequences are best when built as low as possible
in the chimney run to maximize performance.
Do not make support columns of brick, stone or wood.
All support columns must bear onto proper noncombustible
foundations.
Isokern Offset Chimney Block Installation:
Isokern offset chimney blocks are stacked in a stair step
fashion with each successive block overhanging the previous
offset block by three inches (3”), allowing the flue to rise at an
angle of thirty (30°) degrees off of vertical. (Figure 83)
When building offset sequences check the interior flue
alignment as each offset block is set to avoid creating overhanging
ledges on the inside of the flue. Such internal overhangs will
inhibit flue drafting.
Each offset block is to be set fully in a bed of Earthcore
Mortar, completely sealing each offset block to the underlying
component.
Offset chimney block sequences can be built to shift the
chimney run to the left, right or to the rear of the firebox/smoke
dome assembly.
Offset blocks can be set in a spiraling rotation, thus
moving the chimney to a point that is diagonally away from its
starting point.
Offset blocks require 1 1/2” to combustible framing.
Offsets to the Left or Right:
When offsetting chimneys to the left or right of the
firebox it is not possible to build a support column directly under
the third offset block.
To create proper support, construct a support column
against the firebox from bearing up to the level of the smoke
dome. Bridge from the column over to bearing on the smoke
dome with two pieces of four inch (4”) by four inch (4”) by five-
eighths inch (5/8”) steel angle. (Figure 84)
On the steel angles build a masonry or steel support
column up to the underside of the third offset block in the
sequence. (Figure 84)
NOTE:
For offset chimney block sequences that clear the side
wall of the firebox below, it is allowable to support the first offset
block that clears the the firebox side wall and then to proceed
with supports at each third offset block thereafter. (Figure 85)
FIGURE 83
FIGURE 84
FIGURE 85
3"
Summary of Contents for Magnum 86072-60
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