DM 54 Chimney System: Load Capacity - Brick Ledge
52
FIGURE 105
It is relatively simple to calculate the total physical
load on the brickledge resulting from the physical weight of
applied veneers built to code height, however, calculation val-
ues for load to the brickledge due to wind are site specic and
based on local variables such as wind speed zone, exposure
classication, eave height and roof pitch of the structure, as
well as height of chimney mass exposed to wind.
Important: The total load delivered into the brickledge is job
specic and will be the sum of:
(1) the physical load from veneers, plus
(2) the load due to wind.
The total of physical load and load due to wind must
not exceed ninety four hundred (9400) pounds.
Notes:
Calculation of wind load requires the services of a
local structural engineer who can evaluate wind load for the
specic structure and site in question.
Do not subject the brickledge to unequal loading
when applying veneers. Build veneers equally on all four sides
of the brickledge.
Brickledge Veneer Finish and Flashing Details:
When applying brick, stone or other masonry veneer
to the Isokern brickledge standard good building practices for
masonry veneer work should govern weather-proong details
and the placement of ashings.
A typical ashing detail would be to eld fabricate an
aluminum or galvanized sheet metal ashing, approximately
thirty-two inches (32”)square with a twenty inch (20”) square
hole in it, to serve as an inner ashing.
(Figure 106)
Place the inner ashing on the rst DM 54 outer cas-
ing block that fully clears the roof line. Keep the ashing to
about a one-half inch (1/2”) lap onto the top of the outer casing
block. The twenty inch (20”) square hole in the ashing should
t to the outside of the alignment grooves on top of the DM 54
outer casing. Continue the DM 54 chimney up to the required
termination height.
Once the masonry veneer is in progress the inner
ashing is set into a horizontal joint in the veneer at a level
above all other roof deck ashings, chimney-to-roof ashings
and counter ashings. Weep holes should open to the outer
face of the veneer at vertical mortar joints located at the level
of the inner ashing. (Figure 107)
Where moisture may develop between the DM
54 outer casing and the chimney veneer, inner ashings as
described above will help to divert such moisture to exterior
face of the veneer by way of the weep holes and thereby keep
such moisture from working its way down between the veneer
facing and the DM 54 outer casing and into the interior of the
structure below.
Load Capacity for DM 54 Brickledge:
The sources of load delivered into the Isokern brick-
ledge are:
(1) the total physical load of brick, stone or other masonry
veneer on the brickledge, and
(2) loading due to the force of wind delivered against the ex-
posed height of the chimney mass.
The required height of any chimney is governed by
applicable local building codes. The overall nished
height of any chimney varies based upon site-specic
conditions (eg. elevation of roof line, roof pitch, distance
of the chimney from the ridge, etc.).
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