FireNuggets, Inc
May 2017
Simple blue roof construction utilizing a modular
array of metal trays containing gravel ballast.
controller to regulate the discharge of water flow
from rooftops. Commonly, a controller actuated
pinch valve is positioned on the roof leader pipe.
The controller monitors hydraulic head pressure
on the valve. When water reaches a pre-
determined pressure, the valve is automatically
opened by the controller to allow water to pour
off the roof. Passive systems use dams, weirs
and restrictor plates at the roof drain inlets to
create temporary ponding and gradual release
rates of stormwater from the roof.
Modular Design Technique
Simple blue roof construction consists of a
modular tray assembly made of lightweight
metal or plastic containing ballast. The depth of
the ballast can vary depending upon water
By Firefighters, For Firefighters
detention goals. Rainwater is stored within the
ballast void space and to the top of the tray.
Interconnected tray systems act as a large
reservoir for rainfall. This approach provides
flexibility in both the size and configuration of
the water detention system.
Rooftop water detention also requires the
installation of a protective secondary
waterproofing membrane roofing system placed
below the trays. Requirements for additional
rooftop equipment can be avoided through
appropriate positioning of the trays. The trays
can be directly attached to the roof or anchored
via the sole use of the ballast. Modular tray
design provides dependable drainage at low
cost with minimal maintenance. Blue roofs can
be combined with green roofs to improve
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