BOX GUTTER AND RAIN WATER HEAD DESIGN TO AS/NZS 3500.3:2015

Diagramaic shape of Given Data (Not to scale)

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Ah
Av
Ac
LHS
RHS

=
=
=
=
=

Area Horiz
Area Vert'l
Area Cment
Left hand
Right hand

sq.m.
sq.m.
sq.m.
side
side
Design Storm Intensity (ARI 100) I = mm/hr
Catchment Areas as shown in the diagram.
Calculate roof rise areas.
Roof Slope LHS = 2 deg  Therefore Av1 = Ah1*tan(Slope) sqm
Av1 = 111*tan(2)
= 3.9 sqm
Roof Slope RHS = 5 deg  Therefore Av3 = sqm
Av3 = 22*tan(5)
= 1.9 sqm
Calculate catchment area for each wind direction
Ac = Ah + 1/2(Av facing wind - Av causing rain shadow)
wind from LHS Ac(LHS) = 111+22+0.5*(1.9+22-3.9-11)
= 137.5 sq.m
wind from RHS Ac(RHS) = 111+22+0.5*(3.9+11-1.9-22)
= 128.5 sq.m
wind from front Ac(front) = 111+22+0.5*(20-0)
= 143 sq.m
Worst wind direction is from the front Ac = 143 sqm.
Design Flow Q = I*Ac/3600 Litres/sec
= 330*143/3600 Litres/sec
= 13.1 Litres/sec
Box Gutter Depth
From Fig I1 (Interpolating where necessary)
Using :- Gutter Slope 1 in
and Gutter Width W = mm
from fig I1 Minimum Gutter Depth d = mm

Selected down pipe size = mm
From fig I3, Rain water head Depth (Interpolating where necessary) = mm
Rain water Head Depth increased to comply with Note 1 Fig I2
(RWH depth to be >= 1.25*DP dia.)

=

mm
= 188 mm
From fig I3, Rain water head Length at slope 1:200 = mm
Rain water Head Length increased to fit the DP 150 +20 = 170 mm
Rain water Head Width = 300 mm

### Summary

Down Pipe Size = mm
Box Gutter Width = mm
Box gutter minimum Depth = mm
Rain Water Head Depth = mm
Rain Water Head Length = 170 mm
Rain Water Head Width = mm

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