DCI Products RafterVent - Manual

1 March/April 2007
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CoastalContractor
I
In the Ocean State — where wind-swept
rains aren’t restricted to nor’easters, tropi-
cal storms, and hurricanes — I count on
a vented rain screen coupled with care-
fully detailed flashings to keep water out
of walls.
A rain screen is a cladding system with
a vent space (or a series of vent channels)
between the back side of the cladding and
the weather-resistive barrier. Openings
along the top and bottom of the vent
space let air flow freely. This vent space
provides a channel for any water that gets
past the cladding surface to drain out, and
the air flowing through this space carries
away moisture vapor that dries off the
back side of the siding. In both instances,
the vent space reduces the chance of
water and moisture vapor being driven
into the wall cavity by wind or sunshine.
Installing any cladding as a vented rain
screen is the best way to make the
cladding last. However, it’s easier to do
with lap sidings than with shingles. Lap
siding, such as cedar clapboard and fiber-
cement planks, easily bridges air channels
between vertical furring strips nailed over
studs. But a vented rain screen with side-
wall shingles requires horizontal furring,
which presents some complications.
RAIN-SCREEN OPTIONS
I’ve built cedar-shingle rain-screen sidings
in three ways. The differences mostly
involve the material that forms the vent
space, but this inevitably affects other
details as well.
Vented furring strips. The first time I
built a cedar-shingle vented rain screen, I
laid shingles over a series of back-kerfed
1x3 furring strips (Figure 1). These back
by Mike Guertin
Best-Practice
Wall Shingles
A rain screen offers the ultimate defense against
water intrusion, provided you get the details right
FIGURE 1. The author’s first experiences with venting shingles relied on
back-kerfed 1x3 furring strips. These back kerfs are essential for allowing
water to drain out and air to flow between the horizontal strips, but cutting
the kerfs with a dado blade in a radial arm saw proved too labor intensive.