Installation Guide

COLD WEATHER ROOF
SYSTEM DETAILS
Western Red Cedar shingles and shakes are
an excellent roofing material for cold
weather areas that experience heavy
snowfall and severe temperature extremes.
A natural wood product, they offer the
advantages of durability, superior wind
resistance, and good thermal and acoustical
properties. As with any other roofing
material, however, their best performance
depends upon proper design, sound
construction practice, and correct
installation.
In cold weather areas and particularly in
mountain regions that experience very
heavy snowfall, the cold weather roof—or
vented roof system—is recommended
(Figure 19). The principle of this system is
to allow a constant flow of cold air above
the insulation but below the roofing
material. With other roofing systems, ice
build-up along the eaves can be a problem.
Heat escapes from the insulation and melts
snow which runs down the roof to the cold
overhangs where it freezes, causing water to
back up and sometimes penetrate the roof
systems. A properly installed, vented cold
weather roof eliminates this problem.
Venting space should be sufficient to allow
a free flow of air from eave to rooftop.
There are a number of important
considerations that influence roof
performance in areas of heavy snowfall,
particularly mountain regions.
Design, of course, is very important. The
steeper the roof the better the
performance. Chimneys should be located
at the ridge or gable ends away from
possible snow pressure on the slopes.
Plumbing pipes should be located on
inside walls and should be extended
between the rafters and vented at the ridge.
If this is not practical then plumbing vent
pipes should be galvanized iron, well
anchored inside the roof. (Plastic vent
pipes extending through the roof may be
dislodged by sliding snow.)
Vented space
Spaced
sheathing
Rafter
Insulation
Vented space
Trim
Gable Roof
Vented space
Cap
Screen
Vented space
Decking
Screen
Rigid insulation
Shed Roof
Double
starter
course
Cedar shingles
or shakes
(applied as per
specification)
Cold Weather Roof Systems
Fig. 19: Cold Weather Roof Systems
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