The
BauderBLUE Roof System is a sustainable drainage method designed to
attenuate and manage stormwater on a flat roof over a 24-hour period via a
restrictive flow outlet.
A BauderBLUE roof is
designed
specifically for each individual project. It is a solution for urban areas
where options for ground-based attenuation systems are limited, and in
particular, where construction is being carried out within flood sensitive
areas.
The BauderBLUE roof
system has no moving parts, is simple to install and easy to maintain. It
is designed to slow the release of rainwater into the drainage system and to
discharge the water completely over a 24-hour period.
Development and
expansion of towns and cities has seen exponential use of impervious surfaces
causing artificially high rates of rainwater runoff. In measures to prevent
flooding, planners are restricting the amount of rainwater leaving a site via
the drainage system which can be limited to 5-10 litres per second per hectare,
the same flow rates for regional greenfield sites.
This rooftop
sustainable urban drainage system (SuDS) has weight load implications and the
project’s structural engineer will need to be engaged with the design process
from an early stage.
The specifically
engineered outlet restricts the discharge of stormwater to a calculated and
predesigned flow rate to significantly slow down the volume of water leaving
the site. As the storm passes, water continues to discharge from the roof at a
controlled rate which helps to avoid downstream or localised flooding.
The
BauderBLUE Roof system can be constructed at either rooftop or podium
level. The designed void space between the flat roof waterproofing membrane and
hard or soft landscaping finish allows the stormwater to attenuate.
Fundamentally, a
blue roof is designed to attenuate water and should not be considered as a
water storage solution.
The Bauder Blue Roof
is designed for use with either the Bauder Total Green Roof System as a warm
roof construction or the Bauder Hot Melt cold roof construction. The design of
the blue roof requires:
- Specific flow restrictor
outlets to meet the requirements of planning for total allowable water
discharge.
- Emergency overflows included
in the design, unconnected to the blue roof outlets, to discharge the
rainwater should the maximum height of rainwater attenuated be reached.
- Free-flowing
multi-directional water movement within the void space to the specifically
engineered outlets.
- Minimal or elimination
of penetrations in the area where water is to be attenuated, other
than the rainwater outlets or emergency overflows that are required for
drainage functionality. In some instances, it may be possible to
individually isolate the roof penetration from the blue roof SuDS to
prevent any possible water ingress from contaminating the insulation.
- Roof design must adhere
to the British Standards and Systems Codes of Practice for
waterproofing and roof detailing.
The baseplate of the
blue roof system sits within a standard Bauder outlet and slows water from
leaving the roof via a calculated number of restrictive flow holes. The number
of flow holes, up to a maximum of 12, is calculated to reflect the SuDS calculation
for permitted discharge rate for the site.
If, in the event of
a storm of greater magnitude than 1 in 100 years plus 40% for climate change,
then water will evacuate the roof through the central overflow.
The design of every
Bauder blue roof is individual to the project and geographical
location. We use details of the roof area and the drainage requirements
for the site to produce a roof specific discharge report to show the following:
- Storm profile for the roof
during a 1 in 100-year storm event + 40% for climate change.
- Maximum attenuation volume on
the roof.
- Number of outlets required,
complete with an assigned number of control holes, restricting the flow of
water in line with the discharge rate for site.
- The depth of void required on
the roof on to which any landscaping finish can be installed.
The report and
series of calculations allows us to produce the most effective scheme for your
project.
The Bauder blue roof
outlet overflow is inserted into the baseplate and measured, marked and cut to
the specified Hmax for the roof. The entire blue roof outlet is protected with
the Bauder ALU250 Inspection Chamber which allows for ease of access during
regular maintenance.
Blue roofs require
regular maintenance and inspection of the outlets to ensure the drainage holes
are free of debris or blockages. Inspections should take place following any
significant storm event, any notable traffic or remedial works that take place on
or around the roof, and following leaf fall during the autumn months to ensure
leaf litter is not causing obstruction.
