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Wood Truss Details3.3
Terminal Hip Framing-The hip jacks extenddirectly to the peak.
The distance from the end wallto the face of the girder is equal to
one half the span,provided the slopes are equal. The last
standardtruss is designed as a girder to carry the loads
Step Down Hip Framing-The Step Down hip is themost versatile of
all hip types. Each of the stepdown trusses is the same span and
has the sameoverhang as the adjacent standard trusses, butdecrease
in height to form the end slope. The girderlocation is generally
from 8 to 12 feet from the endwall and is determined by the span to
depth ratio.The corner and end jacks are normally pre-built.
Midwest Hip Framing-Developed to create amore uniform
configuration of each of thetrusses in the hip. This hip type also
providesfor a more uniform structure for attaching thedecking.
California Hip Framing-Although not usedextensively this is
another alternative to the stepdown hip. The base portion of each
truss inside thegirder is the same, except that the sloping top
chordof each successive truss is extended upward greateramount to
form the slope intersection. Corner andend jacks are used to form
the area outside thegirder.
Hip FramingTrussed hip framing offers the advantage of clear
span, an eave or facia line at the same elevation around the
building, andthe speed of pre-built components. The end slope may
be equal to or different from the side slope. The ceiling line may
beflat or sloped. Sloped ceilings have limitations; therefore,
consult with your truss designer.
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Wood Truss Details3.3
Girder TrussesGirder trusses have two main purposes. The
first(Girder Truss A) exists in L, T, H, and U shapedbuildings to
eliminate the need for an interior load-bearing wall. The girder is
used to support one end ofthe intersecting trusses. The trusses are
carried on thebottom chord of the girder by hangers.The second use
of a girder truss (Girder B) is to supportperpendicular framing in
hip roofs. In some plans girdertruss A and B may be on in the same.
The hip framing iscarried on both the top and bottom chords of the
girdertruss by nailing or by hangers.Girder trusses, because of the
heavy loads they support,are generally multiple units with larger
chord membersthan the adjacent trusses. Generally, because of
theconstruction of girders, overhangs are not used.The girder truss
may also be designed for drag strutloads which are calculated and
specified by the buildingdesigner.
Valley Framing SetsValley framing sets are primarily used to
form a ridgeline by framing over the main roof whereperpendicular
building sections intersect.Valley trusses are set directly on the
main trusses.Sheathing is required on the top chords under
valleyframes to continue the lateral bracing of the maintrusses.
The bottom chords of the valley trusses canbe bevelled to match the
slope of the roof below.
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Wood Truss Details3.3
Gable FramingGable ends when not configured in triangles as a
truss are more related to stud walls. However, they are
structuralelements and are analyzed to resist wind and seismic
loads as noted on the truss design. The web design may bedetermined
by the type of siding or the need for a louver in the end of the
building. The type of gable required iscontrolled by the end
overhang and the need to match a soffit line.
Transition GableA transition gable is required when a run of
smaller spantrusses leads up to parallel longer span trusses. It
will facelateral wind loads in the area where it is not shielded by
thesmaller span trusses and have to carry the roof load where
itdoes not have continuous support
Clear Span GableA clear span gable must span from one wall to
another. Ithas to have diagonal webs to help distribute the load
out tothe walls, but it also needs to have vertical gable studs
tohelp the gable sheathing resist lateral wind forces.
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Wood Truss Details3.3
Cantilevers and OverhangsCantilever conditions are common
intruss designs. A cantilever exists whenthe bearing wall occurs
inside of thetruss overall length, excludingoverhangs.When the
bearing is located under thescarf line of the truss, no heel
jointmodification is needed. Wedge blocksor sliders are used to
stiffen the heelpanel when the bearing is moved insidethe scarf
line. Wedge blocks act tostiffen the heel joint and are connected
tothe top and bottom chord with connectorplates located over or
just inside thebearing. Sliders allow longer cantileversby
stiffening the top and bottom chordsin the heel panel.
OverhangOverhang
Overhang Overhang
Overhang Overhang
The additional web is addedwhen the cantilever distance istoo
long for use with the wedgeblock or reinforcing member.
THIS MEMBER OFTENREQUIRES CONTINUOUSLATERAL BRACING
VariesUsually12
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Wood Truss Details3.3Typical Flat Truss End Details
Mansard FramesMansard details are normally built onto the truss.
However, there are design situations where it is more appropriate
tohave the mansard frame installed independent of the roof framing.
Those occasions might be when the use of the buildingdictates a
construction type requiring masonry exterior walls and a
non-combustible roof.
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Wood Truss Details3.3
Typical Roof Truss Bearing Conditions
Typical Bottom Chord endcondition
Typical Bottom Chord endcondition without overhang
Raised Heel with or without asloped ceiling
Bottom Chord bearing in ahanger
Tail Bearing TrayIf the room calls for a tray ofcoffered ceiling
very close to thebearing the truss can look like this.It may
require a scab to be attached.Consult with your truss designer
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Wood Truss Details3.3
Typical Roof Truss Bearing Conditions
Top Chord Bearing Mid-Height Bearing
Leg-Thru Bearing Flat Roof Parapet
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Wood Truss Details3.3
Piggyback TrussesWhen roof trusses are too tall to
bemanufactured and/or delivered, trussmanufactures will supply
piggybacktrusses. The piggybacks below areshown above the roof so
that thepurlin and bracing system can beseen. Special diagonal
bracing onthe underside of the top chords helpsbrace the purlins
themselves, andkeeps them from shifting out ofplane. The preferred
method is tosheath the top chords of the bottomtrusses. The
piggyback trusses canbe designed using either verticalstuds or
diagonal webs.
Detail of the bracing system,with purlins and diagonal
braces
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Wood Truss Details3.3Wood Truss Floor Systems
Floor systems can betrussed, conventionallyframed, or built
withengineered wood products.Both trusses andengineered wood
productsare engineered and havewider nailing surfaces forthe floor
decking. Trussescan be built with openchases for ductwork andhave
natural open spacesfor plumbing and electricalwiring.Floor trusses
can bemanufactured with manydifferent possible endconditions to
accommodatedifferent installation needs;around raised
walls,pocketed beams, headersaround stairways, etc.
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Wood Truss Details3.3Wood Truss Floor Systems
Parallel stairwell openings do not present aproblem. Multiple
ply floor trusses mayrequire special connection details between
theplys. Special connections will be specified onthe design.
Perpendicular stairwell openings mayrequire addition posts or
bearing walls. Allloads from stairs and surrounding wallsmust be
considered for correct floor trussdesign. Trusses may be supported
as topchord bearing or by hangers. Headers maybe supported by
approved hangers
Typical DuctOpening Sizes for4x2 Floor Trusses.
Openings and weblocations may varydepending on loads.
If a certain opening isrequired specify it onthe drawing.