Autumn '21

Contact
ABG Geosynthetics:
www.abgltd.com/products/
blueroof.html
Tweet: @ABG_ltd
Water quality
Installing the blue roof system has a
positive impact on the quality of the
water discharged. Before the water
reaches the roof outlet, it passes
through several filtration layers that
remove particulates and pollutants.
Even if the surface finish isn’t green, the
water passes through at least two layers
of geotextile filtration. The water is
treated to such a degree that it usually
reaches the level required in treatment
train stage one of the SuDS process,
allowing water to be released from the
roof directly into the river or sewer
systems.
Waterproofing
The waterproofing membrane / system
selection depends on the type of roof
construction, but a BBA certified system
(or similar), accredited for use to zero
falls is recommended. ABG’s blue roof
system is compatible with both warm
and inverted roof constructions, and uninsulated
podium constructions. As with
traditional roof types, the waterproofing
should be detailed to standard height
above the final floor levels, with the
recommended test methods adhered
to ensure integrity, and a full structural
deflection analysis.
Above: Composite decking surface finish
for amenity area; Top: Extensive green roof
finish for promoting new ecosystems.
Installation process, access and
maintenance
Blue roof systems should be fitted as
part of an approved installer process
and supervised by the manufacturer’s
installation team, with post installation
quality checks and sign off procedures.
The system must also have a provision
for regular maintenance and therefore
future access should be considered to
suit the final finish, as with all roofing
applications. Decking areas, paved
podium decks and ballasted
roofs are relatively low
maintenance, whereas
green roofs usually require
twice yearly maintenance
visits to monitor and
remove invasive species
and trim vegetation.
Thermal performance
Currently the components of a blue or
green roof are not considered as part
of the roof build up when calculating
thermal performance, so the insulation
design and specification is the same
as for a traditional roof design. Despite
the UK building regulations currently
making no allowance for a blue or
green roof, research shows that the
introduction of layers of drainage,
growing media and vegetation do
have a positive impact on the thermal
performance of a roof, with the most
significant benefit a reduction in solar
gain.
Summary
Blue roofs are rated as one of the
most sustainable, ‘at source’ SuDS
techniques and can often meet all
four of the objectives for good SuDS
design. When implemented correctly
they form an integral source control
and attenuation element for
modern developments.
Left: Blue roofs address the
‘four pillars’/objectives of
good SuDS design.
www.greenscapemag.co.uk • GREENSCAPE AUTUMN 2021 35