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3.18
ROOF TRUSS SYSTEMS - FRAMING STYLES
Gable and Valley Systems
Gable System
A gabled roof system allows a framed area to
have a vertical plane coming off an end wall.
This framing system gives the appearance that
the vertical plane of the end wall extends up to
the roof plane. The trusses in this system span
the width of the roof area and can be of the same
profile throughout the length of the building
provided other interior or exterior geometry
changes do not occur. The first truss is located
on the end wall and is called the gable end truss.
The gable end truss, unlike the other trusses in
this system, is typically supported continuously
by the end wall for vertical loads, and resists the
horizontal wind load and transfers that load to
the building diaphragm. Because of its unique
role, the gable end truss may have a different
web pattern and may require different types of
bracing than the common trusses. A gable end
truss will typically have vertical webs spaced at
16" or (no more than) 24" on center, to resist
lateral wind loads and to accommodate the
attachment of sheathing. Gable end truss
vertical webs, when sheathed, will act like wall
studs.
Valley System
Valley trusses are generally supported by the
clear-span trusses below to form new,
intersecting ridge lines. Valley trusses can be
attached directly to the top chord of the
supporting trusses below or directly to the roof
decking (see photo).
Note: Truss bracing not shown for clarity.
Typical Gable & Valley System
ENGINEERED BY ALPINE
S P E C I F Y I N G / D E S I G N I N G
