Framing With Roofs

Framing With Trusses: Roofs

10 Encyclopedia Of Trusses

Trussed hip framing offers the advantage of clear span, an eave or fascialine at the same elevation around the building, and the speed of pre-builtcomponents. The end slope may be equal to or different from the sideslope. The ceiling line may be flat or sloped. Sloped ceilings havelimitations, therefore, consult the truss designer.

Hip Framing

Best suited for relatively short spans of 26'-0" or less, the hip jacksextend directly to the peak. The distance from the end wall tothe face of the girder is equal to one half the span,provided the slopes are equal. The last standard truss isdesigned as a girder to carry the loads transferred bythe hip jack.

Terminal Hip Framing

Step Down Hip FramingBetter suited for longer spans, the Step Down hip is the

most versatile of all hip types. Each of the “step down”trusses is the same span and has the same overhang asthe adjacent standard trusses, but decrease in height to

form the end slope. The girder location is generally from 8to 12 feet from the end wall and is determined by the span to

depth ratio. The corner and end jacks are normally pre-built.

The Midwest type hip framing was developed to create amore uniform configuration of each of the trusses in thehip. This hip type also provides for a more uniformstructure for attaching the decking. Span capability isthe same as the step down hip.

Midwest Hip Framing

California Hip FramingAlthough this type hip framing is used as an alternative to

the step down hip, the California hip is similar in spancapability and field installation. The base portion of eachtruss inside the girder is the same, except that the sloping

top chord of each successive truss is extended upwardgreater amounts to form the slope intersection. Corner and end

jacks are used to form the area outside the girder.


11Alpine Engineered Products

Girder TrussesGirder trusses have two main purposes. The first (Girder Truss A)exists in L, T, H and U shaped buildings to eliminate the need foran interior load-bearing wall. The girder is used to support oneend of the intersecting trusses. The trusses are carried on thebottom chord of the girder by hangers.The second use of a girder truss (Girder Truss B) is to supportperpendicular framing in hip roofs. In some plans girder truss Aand B may be one in the same. The hip framing is carried on boththe top and bottom chords of the girder truss by nailing or byhangers.Girder trusses, because of the heavy loads they support, aregenerally multiple units with larger chord members than theadjacent trusses. Generally, because of the construction of girders,overhangs are not used.The girder truss may also be designed for “drag strut” loads whichare calculated and specified by the building designer.

Valley Framing SetsValley framing sets are primarily used to form a ridgeline by framing over the main roof where perpendicularbuilding sections intersect.Valley trusses are set directly on the main trusses.Sheathing is required for main trusses with 2x4 topchords, and is recommended for other top chord sizes,under valley frames to continue the lateral bracing ofthe main truss top chords. The bottom chords of thevalley trusses are generally beveled to match the slopeof the roof below.

Girder Truss AValley Trusses

Standard Truss

Flush Cut TrussValley Frames

Sheathing

Girder Truss A

Valley Trusses

Girder Truss A

Girder Truss B



Gable ends when not configured in triangles as a truss, are morerelated to stud walls. However, they are structural elements andare analyzed to resist wind and seismic loads as noted on the trussdesign. The web design or framing pattern is determined by the

type of siding, either horizontal or vertical, and the need for a louverin the end of the building. The type of gable required is controlled bythe end overhang and the need to match a soffit line.

Standard GableStud spacing as necessary to support siding.

Standard Gable Framed ForRectangular Louver

Standard Gable Framed ForTriangular Louver

Dropped Top Chord GableIllustrated with studs. Also available with framing for rectangular,square or triangular louver.

Gable Framing

A reinforcing member maybe required on some gable

end vertical members.

2x4 Ladder Frame(Outlooker)

Gable End

2x4 Block

2-16d @24" O.C.

Truss

2x4 LadderFrame

(Outlooker)

Gable End

2-16d @ 24" O.C.

Truss

2x Block

Standard Truss

2x4 Ladder Frame(Outlooker)

Rafter

Standard Gable

Standard Truss

Drop TopChord Gable

Rafter

Clearspan GableUsed when the gable wall does not provide continuous bearingsupport for the gable framing.

8” Typical


13Alpine Engineered Products

Panel Framing For Flat Roofs

Girder Truss4x8

StructuralPanel

Stiffeners@ 16" or 24" O.C.

Trusses@ 8' O.C.

Metal JoistHangers

Long Directio

n

Of Panel

12Slope

Slope12

OverhangVaries

Slope12

12Slope

OverhangVaries Cant. Varies

Slope12

12Slope

Slope12

12Slope

Additional Information available fromThe American Plywood Association

Mansard details are normally built onto the truss. However, thereare design situations where it is more appropriate to have themansard frame installed independent of the roof framing. Thoseoccasions might be when the use of the building dictates a

construction type requiring masonry exterior walls and a non-combustible roof, difficult erection and handling situations orremodeling. Building codes may require special load cases.

Mansard Frames

Typical Sloped Flat Truss End Conditions



Cantilever conditions are common in trussdesigns. A cantilever exists when the bearingwall occurs inside of the truss overall length,excluding overhangs, such as to form a porchor entrance way.When the bearing is located under the scarfline of the truss, no heel joint modification isneeded. Wedge blocks or sliders (reinforcingmembers) are used to stiffen the heel panelwhen the bearing is moved inside the scarfline. Wedge blocks act to stiffen the heel jointand are connected to the top and bottomchord with connector plates located over orjust inside the bearing. Sliders allow longercantilevers by stiffening the top and bottomchords in the heel panel. Correct plating ofsliders varies from normal heel joints.

Cantilevers and Overhangs

Cantilever End Details For Flat Roofs

Long Cantilevers

Typical Methods Used In Cantilever Conditions

Overhang

Slope12

Overhang

Slope12

Overhang

Slope12

Overhang

Slope12

VariesUsually

12"

Slope12

Overhang

Slope12

Overhang

Slope12

Exact Method SubjectTo Final Truss Design

The additional web (strut) is added whenthe cantilever distance is too long for usewith the wedge block or reinforcingmember. This member often requirescontinuous lateral bracing (CLB).

Cant. Dim.

Cant. VariesCant.

Varies

Slope12

12Slope

Cant. Varies

Cant.

Slider(Reinforcing Member)

Cant.Cant.

Wedge

Framing With Roofs

Documents

Transcript of Framing With Roofs