Saturday, February 9, 2013

Dormer Shed Roof Rafter calculator


Rafter Tools

This Dormer Shed Roof Rafter calculator will return the roof framing trigonometry & geometry details for:

  1. Dormer Shed Roof Rafter Length
  2. Dormer Shed Roof Miter Angle (Rake Cut Angle)
  3. Dormer Shed Roof Sleeper Bevel Length
  4. Dormer Shed Roof Intercept Run ( Intersection of Dormer Roof and Main Roof)
  5. Main Roof Intercept Length (Useful for laying out Dormer Sleeper that is not Beveled)









Using the Law of Sines 
c = ( a × sin( C ) ) ÷ sin( A)

c = Dormer Roof Rafter Length
C1 = 90° - Dormer Roof Pitch Angle
C2 = 90° - (Main Roof Pitch Angle - Dormer Roof Pitch Angle)
C = 90° - Dormer Roof Pitch Angle + (90° - (Main Roof Pitch Angle - Dormer Roof Pitch Angle))
C = C1 + C2
A = Main Roof Pitch Angle - Dormer Roof Pitch Angle  
a = Dormer Roof Run

Dormer Roof Rafter Length = (Dormer Roof Run × sin(90° - Dormer Roof Pitch Angle + (90° - (Main Roof Pitch Angle - Dormer Roof Pitch Angle)))) ÷ sin(Main Roof Pitch Angle - Dormer Roof Pitch Angle )
or
Dormer Roof Rafter Length = (Dormer Roof Run × sin(C)) ÷ sin(A)
or
 
Dormer Altitude = sin(Dormer Roof Pitch Angle) ×  Dormer Run
Dormer Altitude Run = Dormer Altitude ÷ tan(Dormer Roof Pitch Angle)
Dormer Miter Cut Angle =  Main Roof Pitch Angle - Dormer Roof  Pitch Angle
Main Altitude Run = Dormer Altitude ÷ tan(Dormer Miter Cut Angle)
Dormer Rafter Length = Dormer Altitude Run + Main Altitude Run
Main Intercept Run = (Dormer Rafter Length  × cos( Dormer Roof Pitch Angle)) - Dormer Run

An example of the calculated results that you can email yourself in the Rafter Tools app 

Rafter Tools -- Dormer Shed Roof Calculations

  •  Main Rafter Slope Angle
  •  33.69007°
  •  Main Rafter Pitch
  •  8  in\12in
  •  Main Rafter HAP
  •  7 3/4''in
  •  Main Roof Sheathing Material Thickness
  •  1/2''in
  •  Main Roof Rafter Material Depth
  •  9 1/2''in
  •  Main Roof Rafter Plumb Height
  •  11 7/16''in
  •  Main Run
  •  28 1/4''in
  •  Main Intercept Run
  •  32 7/16''in
  •  Dormer Rafter Slope Angle
  •  14.03624°
  •  Dormer Rafter Pitch
  •  3  in\12in
  •  Dormer Rafter HAP
  •  8 7/16''in
  •  Dormer Run
  •  54 ''in
  •  Dormer Roof Rafter Material Depth
  •  9 1/2''in
  •  Dormer Roof Rafter Plumb Height
  •  9 13/16''in
  •  Dormer Sleeper Material Thickness
  •  1 1/2''in
  •  Dormer & Main Roof Plate Line Difference
  •  0
  •  Dormer Rafter Length
  •  84 3/4''in
  •  Dormer Sleeper Bevel Length
  •  4 7/16''in
  •  Dormer Miter Cut Angle
  •  19.65382°
  •  Dormer Rafter Miter Cut Length
  •  28 1/4''in
  •  Dormer Intercept Run
  •  82 1/4''in
  •  Main Roof Slope Intercept Length
  •  29 3/4''in
  •  Dormer Rafter Length To Main Roof Sheathing Without Sleeper
  •  89 1/4''in




 Main Rafter Slope Angle 33.69007° Main Rafter Pitch 8  in\12in Main Rafter HAP 7 3/4''in Main Roof Sheathing Material Thickness 1/2''in Main Roof Rafter Material Depth 9 1/2''in Main Roof Rafter Plumb Height 11 7/16''in Main Run 28 1/4''in Main Intercept Run 32 7/16''in Dormer Rafter Slope Angle 14.03624° Dormer Rafter Pitch 3  in\12in Dormer Rafter HAP 8 7/16''in Dormer Run 54 ''in Dormer Roof Rafter Material Depth 9 1/2''in Dormer Roof Rafter Plumb Height 9 13/16''in Dormer Sleeper Material Thickness 1 1/2''in Dormer & Main Roof Plate Line Difference 0 Dormer Rafter Length 84 3/4''in Dormer Sleeper Bevel Length 4 7/16''in Dormer Miter Cut Angle 19.65382° Dormer Rafter Miter Cut Length 28 1/4''in Dormer Intercept Run 82 1/4''in Main Roof Slope Intercept Length 29 3/4''in Dormer Rafter Length To Main Roof Sheathing Without Sleeper 89 1/4''in

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