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PATTERN RAFTER. Roof plan. Pitch of roof Half span of roof Eaves overhang Rafter spacing Thickness – ridge hip rafters. = 22.5 ° = 2150mm = 300mm = 450mm = 25mm = 35mm = 45mm. Information required. Rise per metre =

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Information required

Pitch of roof

Half span of roof

Eaves overhang

Rafter spacing

Thickness – ridge

hip

rafters

= 22.5°

= 2150mm

= 300mm

= 450mm

= 25mm

= 35mm

= 45mm

Information required


Calculations required

Rise per metre =

rise/m =

True length per metre =

t.l./m =

Set out length of rafter =

set out length =

Tan pitch angle

0.414

1.082

tl/m x half span

2.327m

Calculations required


Bevels required
Bevels required

  • 1. Plumb bevel rafter

  • 2. Level bevel rafter

1.

Rise

2.

Half span


Steel square application
Steel square application

207

Rise/m ÷ 2

1000 ÷ 2

500


Pattern rafter1
Pattern rafter

Set out length

Halfspan


Reduction common rafter
Reduction : Common rafter

Ridge

Half thickness of ridge

Half thickness

ridge measured

square to plumb bevel


Reduction crown end
Reduction : Crown end

Half rafter thickness

Crown end

Half rafter thickness

measured square to

plumb bevel


Creeper spacing calculations

Rafter spacing x tl/m

½ mitre thickness hip

½ rafter thickness

= 0.450 x 1.082

= 0.487

=

= 24.75mm

= 22.5mm

Creeper spacing calculations


Pattern rafter

Crown

end

a

Long point: first creeper

c

Creeper spacing

b

487mm

a

a

c

b

  • c is long point

  • first creeper

  • Half mitre

  • thickness out

  • Half rafter

  • thickness back


Continuous creeper spacing
Continuous creeper spacing

creeper spacing

X tl/m

487mm

487mm

long point

first creeper

487mm

450mm

487mm

450mm

overhang x

tl/m

325mm

450mm

450mm

300mm


Pattern rafter

Summary

  • Set out length and birdsmouth

  • Plumb bevel centre line

  • Reduction crown end

  • Reduction common rafter

  • Continuous creeper reduction

  • Long point 1st creeper

  • Square marks across top

  • edge and label

  • Eaves overhang

  • Mark edge bevel creeper


Produced by john friedman jfriedman@tafensw edu au

Produced by : John Friedman jfriedman@tafensw.edu.au