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RIGHT TRIANGLE and ROOF FRAMING EXAMPLES
Roof Framing Definitions
y (Rise): The vertical distance measured from the wall’s top plate to
the intersection of the pitch line and the center of the ridge.
Span: The horizontal distance or full width between the outside
edges of the wall’s top plates.
x (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.
θ (Pitch): Pitch and Slope are synonymous in modern trade lan-
guage. Pitch/Slope of a roof is generally expressed in two types of
measurement:
1) Ratio of unit Rise to unit Run* — 7/12 or 7 Inch
2) Angle of rafters, in degrees — 30.26°
*Note: 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.
84 — SHEET METAL/HVAC PRO CALC
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