Technical Specifications

EXTERIOR NEW WALL CONSTRUCTION
7
Double Coursing
To obtain an attractive wall characterized by
wide weather exposures and deep shadow
lines, Certi-label Western Cedar shingles and
shakes can be applied double coursed. This
method offers economy because of the wide
exposures of the outer course and the use of
less expensive undercoursing Certi-label
Western Cedar shingles for the under layer
(Figure 7). For double coursing exposure
details refer to the chart on page 12.
In double coursing, the bottom or starter
course is laid triple with two undercourse
Certi-label Western Cedar shingles or one
undercourse Certi-label Western Cedar
shingle over a wood lath and then the outer
course. This gives the bottom course the
same slant as succeeding courses. All outer
courses are applied 1/2" lower than the
undercourse (Figure 7). A straight edge can
be used to facilitate placement and nailing of
both the undercourse and exposed course.
Undercourse Certi-label Western Cedar
shingles are fastened at the top with one nail
or staple in the center. The exposed Certi-
label Western Cedar shingle or shake is face-
nailed with two casing-type nails, driven
approximately 2" above the butt line, 3/4"
from each edge. With Certi-label Western
Cedar shingles wider than 10" drive two
additional nails approximately 1" apart near
the center.
Architect: Tanner and VanDine Architects, Photo: Mark Citret
The CSSB recommends installing over
plywood panel or dimensional lumber
sheathing. If other sheathing materials are
approved for use by your local building
official, the holding power of the fasteners
should also be considered carefully.
Figure 7: Double Coursing
The outer course is applied 1/2" lower
than the inner course as a drip course
to help shed water
Apply nails in
straight line approximately 2"
above shingle butts
Double undercoursing
Plywood panel
or dimensional
lumber sheathing
Number 3 or undercoursing
grade Certi-label
Western Cedar shingles
Type 30 felt
underlayment