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Roof Framing Definitions
Rise: The vertical distance measured from the wall’s top plate to the
top of the ridge.
Span: The horizontal distance or full width between the outside
edges of the wall’s top plates.
Run: The horizontal distance between the outside edge of the wall’s
top plate and the center of the ridge; in most cases this is equivalent
to half of the span.
Pitch: Pitch and slope are synonymous in modern trade language.
Pitch/slope of a roof is generally expressed in two types of measure-
ment:
1) Ratio of unit rise to unit run* — 7/12 or 7 Inch
2) Angle of rafters, in degrees — 30.26°
*The unit rise is the number of Inches of rise per Foot (12 Inches) of unit run. The unit
run is expressed as one Foot (12 Inches).
Plate: The top horizontal wall member that the ceiling joist and
rafters sit on and fasten to.
Ridge: The uppermost point of two roof planes. This rafter is the
uppermost rafter that all Hip, Valley, Valley Jack and Common rafters
are fastened to.
Rafters: Rafters are inclined roof support members. Rafters include
the following types:
• Common Rafter: The Common connects the plate to the ridge
and is perpendicular to the ridge.
• Hip Rafter: The Hip rafter extends from the corner of two wall
plates to the ridge or King rafter at angle other than 90°. The Hip
rafter is an external angle of two planes.
• Valley Rafter: The Valley rafter extends from the corner of two
wall plates to the ridge or King rafter at angle other than 90°.
The Valley rafter is an internal angle of two planes.
• Jack Rafters: Rafters that connect the Hip or Valley rafter to the
wall plate.
• Irregular Hip/Valley Jacks: Jack rafters found in dual pitch or
“Irregular” roofs.
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