Project1_Layout 1 07/05/2013 FLAT ROOFING & WATERPROOFING SYSTEMS
The future is green
In recent years, green roofs have risen in popularity and more and more architects and specifiers are embracing the concept due to their ability
to have a significant effect on a building’s sustainable credentials. Malcolm Grinstead, director of the Mastic Asphalt Council, discusses
The term ‘green roof’ refers to a roof
that is partially or completely covered
with vegetation and a growing medium,
planted over a waterproof membrane.
It may include additional elements such
as roof barriers, drainage or irrigation systems.
Other features that can form green roofs include
‘container gardens’ where plants are maintained
in pots, rooftop ponds and elevated open space
areas that primarily form pedestrian routes on the
roofs of lower level buildings.
The concept of green roofs has been around
for some time, with the first green roofs appearing
in northern Europe. Scandinavia and countries
including Germany, Austria and Switzerland have
a long tradition of using green roofs.
In some countries, legislation has been introduced
to encourage the installation of green roofs,
with many German cities for example, providing
incentives for green roof installation. Around 10%
of all German roofs are now green, and in France
a law has been passed dictating that rooftops on
new buildings built in commercial zones must
either be partially covered in plants or solar
panels. In addition, every newbuild in Stockholm
must incorporate a green roof. Outside Europe,
Canada, USA, Japan and Singapore have all
experienced growth in green roofs.
074 JUNE 2018 RCIMAG.COM
In the UK, the City
of London actively
installation of green roofs for their environmental
benefits. They enhance biodiversity, reduce
rainwater run-off, improve insulation, moderate
the local climate, make buildings more attractive
and provide amenity for residents who may not
have access to private gardens.
The City’s Biodiversity Action Plan 2016-
2020 includes a habitat action plan for built
structures, which encourages the incorporation in
development of wildlife-friendly features such as
green roofs. In 2017, it was estimated that there
was 40,000m2 of green roof space located within
the City of London.
Within densely built-up areas such as the
City of London, it is important that buildings
are environmentally sustainable. With the close
proximity of the River Thames, the abatement of
flood risk is also a significant issue. Green roofs
in the City of London minimise the urban heat
island effect and flood risk, and provide rainwater
Whether intensive or extensive, biodiverse
or brown, it is critical that green roofs are built
on a solid waterproofing foundation. Offering
exceptional durability and outstanding green
credentials, mastic asphalt is an ideal choice for
specifiers seeking an eco-friendly waterproofing
solution for green roof specifications.
Recognised for its environmental performance
and aesthetic properties, a green roof system
laid with a mastic asphalt waterproofing system
enhances the environment, controls storm water
run-off and reduces noise and heat transmissions
by upgrading the acoustic and thermal
performance of a roof.
When contractors use mastic asphalt for a
green roof system, it eliminates the need for root
barriers, which may well have been necessary
had a substitute material been used. Alternative
membranes to mastic asphalt can also be more
prone to site damage leading to potentially
catastrophic and expensive leaks. Mastic asphalt
also offers a safe, flame-free application.
One of the most cost-effective, long-term
waterproofing membranes of its kind, mastic
asphalt is being positively encouraged as an ideal
solution to green roof and other waterproofing
applications. There are many examples
where mastic asphalt has provided effective
waterproofing for over 100 years.
In the unlikely event of a failure, mastic
asphalt’s seamless structure means it can
easily be spot repaired, eliminating the
need for costly wholesale replacement. The
flowing characteristics of the material also
make it easy for installing contractors to
tackle roof surfaces which are complex,
stepped or with multiple protrusions.
In comparison, failure is often found at
the point of detail work in felt or sheet
membrane waterproofing systems, where roofers
have cut and fixed the material to the roof in
A key objective of the Mastic Asphalt Council
(MAC) is to ensure that exceptional quality
and workmanship standards are maintained for
the installation of waterproofing installations
utilising mastic asphalt. To maintain the
industry’s reputation and ensure high-quality
applications, trained craftspeople from MAC
member companies install mastic asphalt under
the council’s strict rules.
Mastic asphalt is carbon neutral and 10 years ago,
the mastic asphalt sector became the first industry
in the world to achieve the CarbonZero standard.
It is 100% recyclable and at the end of its useful
life it can be recycled and broken down into
hardcore or used in roof screeds.
With the future of roofing looking green, the
reliability and integrity of mastic asphalt has seen
more and more architects and designers specifying
this waterproofing membrane for a wide range of
green roof applications, making it their preferred
choice for biodiverse habits that will indeed
benefit us all both now and in the future.