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Green roofs are not a
new concept, indeed they’ve been used in Scandinavian construction for
centuries. However, their surge in popularity here in the UK has been
driven by the increasingly important ecological principles of
conserving water and the creation of sustainable habitats for local
wildlife. Another added benefit is the roof’s ability to help insulate
a building during the winter (thus lowering heating costs) and also
keep it cooler in summer.
Learning to help the
environment
There are many fine
examples of living roofs, notably the brand new Princes Park stadium
in Dartford and Riverhead School in Sevenoaks, the latter designed by
Architects Design Partnership. The curved school roof features a
living ecosystem of sedums which give the new contemporary building
not only a rural aspect but also offer a valuable source of food and
nectar for local butterflies and other insects.
Since it is the younger
generation who will have to live with the way we are affecting the
environment now, it is perfectly apt that the Horniman Museum in
Forest Hill, London also boasts a living roof above its library, built
as part of its Centenary Development. Children visiting the museum are
enthralled by a garden growing up above their heads. Maybe there will
be future architects among them?
Creating your own sky
garden
There are principally
two main types of green roof, intensive and extensive. Intensive roofs
are generally commercial systems, able to support the heavy weight of
a deep growing medium. The structure of the building itself is often
designed to carry this bigger load and planned at the outset.
Extensive systems however, are those generally with a substrate depth
of 20- 100mm (approx ¾” to 4”) deep. This type of green roof is also
the most suitable for the garden and an ideal way of covering an ugly
shed or garage roof.
Before you start on your
green roof project, there are two questions to ask. Firstly, will the
structure you’re covering be strong enough to take the load? Small
sheds are easy to do although garage roofs may need to be checked by a
structural engineer before starting work. Secondly, will the roof be
waterproof when it’s finished?
You can create your own
‘sky garden’ on a shed roof by first applying a butyl liner over the
roof surface – be careful not to nail it to the roof otherwise you’ll
compromise its waterproof integrity. Next, build a wooden framework on
top of the liner made up of small squares, which will hold the growing
medium (soil and crushed brick). Framework depth only needs to be
5-20cm (2” – 8” depending on the type of plants you want to grow).
Bigger plants will need a deeper framework. Fill the frame with the
growing medium and then plant up with sedums and other drought
tolerant plants like alpines and tuft-forming grasses.
Living the high life
Your living roof will
provide you with a wonderful array of seasonal colours and textures
through the year and you’ll probably notice that other wild flowers
start to appear by seed blown in with the wind or dropped by birds.
The wildlife will be quick to find your oasis in the clouds, too. The
marvellous thing about such roof gardens is they require very little
maintenance and can cover unsightly buildings in a way which benefits
local wildlife.
Designers and architects
are making the most of our precious landscape space, be it on the
ground or on the roof. We can all reduce our ‘carbon footprint’ by
designing our gardens in ways which improve air quality and increase
the diversity of the local ecosystem. Only by keeping the environment
at the forefront of design can we create sustainable landscapes and
buildings which benefit not only our standard of living today but also
that of generations to come.
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