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Storm DrainageStorm DrainageA step by step approachA step by step approach
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Determine Location RainfallDetermine Location Rainfall
Where is your building find the rainfall
data for your building location in the
National Building Code
the rainfall intensity is given under the
column:
15 min. rain mm
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Determine roof areaDetermine roof area
Use the roof area directly for flat roofs
if there is a wall that drains onto the roof add
half of the largest wall area to this roof area
lower roof
area
of wall area adds to
lower roof area
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Other rulesOther rules if the roof area is greater than900 m2 or the roof is bigger than
30m in any one direction then
you need a second roof drain
Best practice is to
use minimum two
drains per roof
40 m
25m
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Layout Roof DrainsLayout Roof Drains
Locate the roof drains in the middle of
imaginary panels
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Decide on piping layoutDecide on piping layout
Straight leaders
interferes with space
good drainage with little chance
of overflow
Offset leaders
Flexible layout
Add cleanouts for 90 degreebends
straight
leader
offset
leader
CO
Roof drain
(RD)
RD
cleanout
(CO)
CO
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Lay out drainage pipingLay out drainage piping
Plan view showing roof drains, building
drain and building outline
CO
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Riser view showing cleanouts and building
storm drain
Roof
drain
(RD)
RD
RD
leader
building
storm drain building
storm sewer
1:100 TYPICAL
CO CO CO CO
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Slope of building storm drain and invert
notes.
1:100 TYPICAL
CO CO CO CO
below frost
line
Invert Elev
43.000
Invert Elev
42.840
16.0 m
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Summary of rulesSummary of rules
cleanout at the bottom of all rain water
leaders
insulate rainwater pipes with waterproof
insulation to prevent condensation
maximum 900m2 per roof drain
max 15 m to edge and 30 m betweendrains
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min two drains per roof for best practice
add area of largest adjacent wall to roof
area show invert elevation at building storm
sewer and at farthest end of building
drain(s)
Summary of rulesSummary of rules contdcontd
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Assignment Due FridayAssignment Due Friday
- Include spec sheet- Include spec sheet