34
DM 54 Chimney System: Offset Block (cont.)
Offsets to the Rear:
With straight chimneys the front of the DM 54 outer casing
block sits approximately three and three-quarters inch (3- 3/4”) back
from the front of the smoke dome. This allows for a nominal 4” thick
wall to be flush with the room side face of smoke dome assembly
while the DM 54 chimney passes up the backside of the wall.
For a nominal 2” by 6” wall thickness the chimney can be
offset 3” rearward by placing one offset block as the first chimney
component.
Set the first DM 54 outer casing block flush to the
back end of this offset block. This will leave a distance of 6-3/4”
from the face of the STANDARD firebox smoke dome assembly to
the face of the DM 54 outer casing block. This allows for the smoke
dome to sit flush with the inside face of the 2” by 6” wall and the
straight chimney to run up the outside of the wall. (Figure 56).
For a wall thickness of 9”, nominal 8” CMU plus 1-1/2”
furring strip - first set two offset chimney blocks in sequence,
rearward. This leaves a distance of 9-3/4” from the front face of the
smoke dome to the front face of the DM 54 outer casing once the
outer casing block is set in position. Greater offset distances can be
accomplished by building with more offset chimney blocks.
(Figure 57)
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. (Figure 58)
Plan fireplace and DM 54 chimney systems carefully before
foundations are laid to assure that proper footings are available to
support Isokern offset blocks and chimney run.
FIGURE 57
FIGURE 58
FIGURE 56
