Profiled Sheeting Design Guide: Part 3 - Barbour Product Search

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Fibre cement rainwater systems
Design details
Introduction
Marley Eternit manufacture a comprehensive range
of fibre cement rainwater goods to complement
their range of fibre cement profiled sheeting.
Key
Box = box gutter
HR = half round gutter
BW = boundary wall gutter
VG = valley gutter
This and the following pages provide sufficient
information for the design and specification of
a complete rainwater system.
General guidance
Marley Eternit recommend that designers refer to
BS EN 12056: Part 3: 2000 for design
recommendations for drainage of surface water
from roofs.
However, the following method provides a general
guide suitable for 75mm/h rainfall.
Fig. 1 provides a simple guide to determining the
required sizes of gutter and rainwater pipes from
the length of roof eaves line drained by each outlet
and the length of its upslope (including both slopes
of a roof valley).
To use the nomogram, place a straight edge at the
appropriate points on Scales A and C and read off
the required gutter and rainwater pipe sizes at the
intersection point on Scale B.
Note: Always select gutter and pipe sizes above the
intersection point, never below it.
Scale A Scale B Scale C
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Example
150mm dia.
100mm dia.
75mm dia.
559 x 152 x 406mm BW
305 x 203 mm Box
457 x 152 x 305mm BW
610 x 152 x 229mm VG
406 x 127 x 254mm VG
305 x 152 x 229mm BW
279 x 127 x 178mm BW
457 x 127 x 152mm VG
127 x 152mm Box
200mm HR
150mm HR
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Example:
To find the required sizes of valley gutter and
rainwater pipes for two roof slopes each with a
6
125mm HR
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10m upslope and each 36m long, draining into
6
a common valley.
5
Total upslope length = 2 x 10m = 20m (Scale C).
5
Assume each rainwater pipe drains 12m of gutter
(Scale A).
Drawing the appropriate line on the nomogram
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4
gives an intersection point on Scale B, which
indicates that a 406 x 127 x 254mm valley gutter
and 150mm diameter rainwater pipes are required.
As the valley is 36mm long, three 150mm diameter
rainwater pipes are required. (i.e. 36 ÷ 12).
Meters
3
Gutter length drained
by one rainwater pipe
Rainwater pipe
Gutter
Meters
3
Upslope length
(two slopes at valleys)
Fig.1 Gutter size/roof length nomogram
66 Profiled sheeting design guide