DCI Products RafterVent - Manual (Page 5)

5
part is starting the first two courses at the
bottom; but once they are secured, the
rest of the corner shingles go fine.
Corner boards. Ideally, corner boards
and other trim elements should be
applied over the rain-screen space. They
benefit from the drainage and “back-vent-
ing” just like the shingles. Plus, installing
the trim over the vent material keeps it in
the same plane as the shingles. However,
this is practical only over battens. Over
the less stable spacer mats, the corner
boards are hard to line up.
One way to deal with this is to apply
1 / 4 -inch plywood or OSB spacers to the
building corner, which provides solid nail-
ing and a vent space (Figure 4). I use
4-inch-wide plywood or OSB spacers posi-
tioned 12 to 24 inches apart up both sides
of each building corner. I cut the block
width
1 / 2 inch greater than the corner-
board width and snap vertical plumb chalk
lines over the blocks that give me a refer-
ence for aligning the corner boards. These
spacer blocks are easier to install before
the matrix mat is installed. There’s no need to cut the mats around the blocks
either — just trim at the outside edge.
Horizontal band boards or skirt
boards present a similar challenge. I treat
them the same as corner boards. With bat-
tens, I run one strip at the bottom and
one at the top, which is placed so half the
batten supports the top edge of the board
and the other half is exposed to support
the first course of shingles. When using
Best-Practice
Wall Shingles
March/April 2007
~
CoastalContractor
Corner-Board Detail
End rain-screen mat
at chalk line here
Spaced 1 / 4 " to 3 / 8 "
OSB or plywood blocks
Rain-screen
mat
Corner board
Apply housewrap
on wall first
Midwall
band board
Housewrap
Rain-screen mat
Skirt board
Skirt board
Midwall
band board
DCI CedarVent includes
insect-blocking fabric
Spaced
1 / 4 " to 3 / 8 " OSB
or plywood blocks
Plastic
battens
Z flashing Z flashing
Screen under blocks
protects against insects
FIGURE 4. Corner boards should be
applied over a rain screen just
like the siding. While this is rela-
tively easy with battens, installing
trim over a spacer mat is more
difficult because the pliable mat
doesn’t provide a stable nailing
base. To make it easier, the
author installs 1 / 4 -inch OSB spac-
ers to the building corner before
the matrix mat is installed.
FIGURE 5. Skirt boards over
a spacer mat also get 1 / 4 -
inch plywood or OSB
blocks (far left), while bat-
tens are simply spaced so
half the batten is above
the top edge of the skirt
board (left). In both cases,
a drip cap flashing must
be installed over the hori-
zontal trim board, but this
flashing should not extend
to the sheathing so it will
not disrupt airflow.