Isokern Standard 36 - Offset Block

3”
34
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-ve inches (25”) long. The
fourteen inch hole passes through the block at thirty (30°) degrees. An
offset chimney block can be set as the rst ue component on top of
the replace 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 ue to rise at an angle of thirty
(30°) degrees off of vertical. (Figure 52)
When building offset sequences check the interior ue
alignment as each offset block is set to avoid creating overhanging
ledges on the inside of the ue. Such internal overhangs will inhibit
ue 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 rebox/smoke dome
assembly. Offset blocks can also be set in a spiraling rotation, thus
moving the chimney to a point that is diagonally away from its starting
point.
Offset blocks require a 1 1/2” clearance to combustible
framing.
Offsets to the Left or Right:
When offsetting chimneys to the left or right of the rebox 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 rebox 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 ve-eighths inch (5/8”) steel
angle. On the steel angles build a masonry or steel support column up
to the underside of the third offset block in the sequence. (Figure 53)
Note: For offset chimney block sequences that clear the side
wall of the rebox below, it is allowable to support the rst offset
block that clears the the rebox side wall and then to proceed with
supports at each third offset block thereafter. (Figure 54)
FIGURE 52
FIGURE 53
FIGURE 54