Catchment Area No 111				Job No 007
Building xyz				Date 1/1/2016
				Design: AJB
OVERFLOW DESIGN FOR EAVES GUTTERS to AS/NZS 3500.3:2015
Industrial building for J. Blogs
Blogs Lane - Blogsville.
	Catchment area	A	=	100	sq.m
	Intensity ARI 100	I	=	333	mm/hr
	Coefficient of Runoff	I	=	1
	Roof Slope	S	=	22	deg.
	Roof Slope Factor	Sf	=	1 + 0.5*tan(Roof Slope)
			=	1.2
	Design Catchment Area		=	Sf * A
			=	120
	Roof runoff = Overflow required	Q	=	C*I*A/3600	L/s
			=	1 * 333 * 120/3600
	Therefore total Overflow required		=	11.1	L/s
	Length of eaves gutter		=	11	m
	Therefore Oflow/metre of gutter		=	1.01	L/s/m
	Overflow Methods:
	Manufacturers stated slot capacity		=	0.5	L/s/m
	Oveflow to be taken over the gutter.		=	0.51	L/s/m
	Determine the setdown "h" from AS/NZS 3500.3 Table G1 (Interpolating as required.)
	Is the gutter sloping or level?		=	Sloping
	Therefore	h	=	15	mm
	Is the roof sheeting turned down into the gutter?		=	yes
	From Table G1 Notes: If Roof sheeting is turned down into the gutter. The overflow height may be reduced by about 8mm. Therefore	h	=	7	mm
	"h" < 10 therefore adopt minimum	h	=	10	mm
	Summary
	Setdown adopted		=	10	mm
	Total required Overflow/m for Q100 storm		=	1.01	L/s/m
	Overflow through Slots (from Manufacturer)		=	0.5	L/s/m
	Overflow over the edge of the gutter		=	0.51	L/s/m
	Total designed overflow		=	1.01	L/s/m
	Therefore this system has equal or greater capacity than the Q100 overflow requirement.
	(Note: The setdown "h" is at the upstream end of the gutter.)
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James Crint
Head Honcho
Hydraulic Dept.