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Minimum Pitches & Head Laps

MINIMUM RECOMMENDED HEADLAPS
 
Moderate Exposure less than 56.5 l/m2 per spell
Size (Nominal) Minimum Rafter Pitch
mm 20° 22.5° 25° 27.5° 30° 35° 40° 45° 85°
600 x 350 115 100 90 85 75 75 65 65 -
600 x 300 125 105 90 85 75 75 65 65 -
550 x 300 130 110 90 85 75 75 65 65 -
500 x 300 115 100 90 85 75 75 65 65 -
500 x 250 125 105 90 85 75 75 65 65 50
450 x 300 - - - 85 75 75 65 65 50
400 x 250 - - - 85 75 75 65 65 50
400 x 200 - - - 90 75 75 65 65 50
350 x 250 - - - 85 75 75 65 65 50
350 x 200 - - - 85 75 75 65 65 50
300x200 - - - 85 75 75 65 65 50
MINIMUM RECOMMENDED HEADLAPS
 
Severe Exposure 56.5 l/m2 or greater per spell
Size (Nominal) Minimum Rafter Pitch
mm 20° 22.5° 25° 27.5° 30° 35° 40° 45° 85°
600 x 350 145 125 100 95 85 75 75 65 -
600 x 300 155 135 120 115 105 90 80 70 -
550 x 300 - 135 115 110 100 85 75 65 -
500 x 300 - 120 100 90 80 75 75 65 -
500 x 250 - 130 115 105 100 90 75 65 65
450 x 300 - - - - 105 100 75 65 65
400 x 250 - - - - 95 90 75 65 65
400 x 200 - - - - 105 105 90 65 65
350 x 250 - - - - 80 75 75 65 65
350 x 200 - - - - 90 85 75 65 65
300 x 200 - - - - 75 75 75 65 65

Last Updated: January 06, 2009