Summer '22

of the insulation.
Installing liquid waterproofing means
the membranes are fully bonded to the
substrate. In addition, when detailed
correctly, they are able to withstand
building movement well in excess of
standard tolerances.
Design stage considerations
Plants must be agreed from the outset
as the roof will need to be designed
accordingly. For example, wildflower
meadows are a popular choice for large
roof surfaces, but they need plenty
of moisture, which means designing
the roof to accommodate the load
and providing a deeper reservoir core.
Alpine planting, however, needs much
less water to thrive so this will have less
of an effect on the roof’s load bearing
requirements, but will still need to be
considered.
Is it also vital that location and prevailing
climatic conditions are considered
as these govern the amount of light,
heat, shade and moisture the roof will
receive. Surrounding buildings, which can
influence shade and exposure to winds,
should be taken into account. These
factors must be assessed collectively to
determine the viability of different types
of planting.
Installation considerations
When installing the liquid waterproofing
system, it is important that the detailing
such as upstands, pipe penetrations
and rooflights are designed to take into
account the increased build-up of the
green roof construction.
Building Regulations typically require
the waterproofing detailing to finish
150mm above the finished roof surface,
which in this case would be the green
roof surface and not the surface of the
waterproofing.
In addition, a contractor must ensure
they deliver correct attenuation and
drainage systems in accordance to the
specification to ensure the plant on
Kemper System has been involved with a number of green roof projects throughout the UK.
the green roof is cared for. It’s essential
that not only the contractor, but the
end client is aware of the maintenance
requirements for the green roof after
installation. If this is not addressed, it
could still be within the retention period
of the contractor and responsibility
could fall on them should there be any
issues. It’s always worth checking this
in advance to ensure contractors are
protected.
A watertight solution
The effectiveness of the waterproofing
membrane between the roof substrate
and the green roof system is the most
vital element of the specification. The
membrane should be flexible enough
to cope with any post-build settlement,
durable enough to cope with the
planting’s load bearing requirements and
have a sufficiently long service life to
make the green roof viable.
A common green roof design would
typically consist of an inverted warm roof
build-up with the waterproofing system
applied to the roof substrate, followed
by the insulation, and then the green
roof elements. This can add an extra
layer of protection for the waterproofing
membrane as it is cushioned underneath
the insulation.
However, a liquid waterproofing
solution such as Kemperol V210 or
Kemperol 2K-PUR can be cold applied
either below or above the insulation,
depending on the type of insulation
used. These systems are FLL certified
as root resistant, so there is no risk
of damage even as plants mature.
Kemperol 2K-PUR is also odourless,
adding to its green credentials.
Alternatively, Kempergro from Kemper
System combines recycled, renewable
and sustainable components to provide
a complete waterproof roofing and
green roof system from a single source
supplier.
Specialist advice
Whether you’re planning a green
roof for a city centre building or
family home, seek technical advice
from waterproofing and green roof
specialists. Their knowledge will
ensure your green roof performs to
the required specification, meeting
climatic, aesthetic and biodiversity
requirements.
Contact
Kemper System
W: www.kemperol.co.uk
T: 01925 445532
www.greenscapemag.co.uk • GREENSCAPE SUMMER 2022 27