Landscaping on Top of the
House
Green
Roofs
Thought of landscaping your roof? Now you can.
You can have a roof garden or a greenroof. Both have been
around for centuries, though modern technology has made the
green roof a viable option where it was not before. A roof
garden usually consists of container of plants of various sizes
placed on top of a roof.
What is a greenroof?—essentially it is a
vegetated roof system that is placed over a waterproof
roofing membrane on new construction or an existing
building. The growing media and plants take the place of
conventional roof coverings to protect the roof membrane. The
number of layers and the layer placement vary, but at the very
least all greenroofs include a single to multi-ply
waterproofing layer, drainage, growing media and the plants,
covering the entire landscaping deck surface of the
roof.
Greenroofs generally
fill into one of two categories: intensive or
extensive--
An
intensive or high profile greenroof requires a minimum of
one foot of soil depth. These systems can support a wide
variety of plants, from flowers to small trees, and can be
used to achieve a landscaped surrounding. They look like
traditional roof gardens because a much wider variety of
plant material can be included since growing media depths
are increased.
Architectural accents such as waterfalls,
ponds, etc. are possible and these greenroofs provide
recreation spaces and encourage interaction between people
and nature. Of course, these roofs are relatively flat and
depending on the plants used, the maintenance requirements
can be high.
Extensive roofs –
also referred to as eco-roofs, and low-profile – have thinner
and fewer layers, so therefore they are lighter, less expensive
and very low maintenance.
Extensive greenroofs are built when the key
landscape desire is for an ecological roof cover with
limited human access. The minimum growing media starts at
about 2 1/2” to 6”. These greenroofs can be placed on slopes
of up to 30 degrees, and steeper ones can be installed with
raised grids to hold plants and growing media in
place.
Greenroofs provide
a myriad of benefits—
Provide new
wildlife habitats
Lower the urban
heat island effect by insulating and shading buildings and
improving air quality.
Reduce the
immediate water run-off greatly reducing flow rates. This
also enables the outlets, downpipes, ground drains, sewer
pipes, etc. to be reduced in capacity thereby lowering
construction costs.
Alleviate
pollutants through a garden roof's natural absorption and
reuse of precipitation, eliminating overflow to the
waterways, flooding streets and overflowing
sewers
Provide sound
insulation, reducing indoor noise
pollution
Create
aesthetically pleasing usable space that can generate more
revenue for building owners
Convert normally
unused roof areas for recreational use which saves the
cost of purchasing additional land and can even aid in
planning consent

Another large
benefit is that garden roofs can save you – the building
owner - money. Because of their insulating properties,
garden roofs have been proven to reduce heating and
cooling costs, and significantly slow a building's heat
gain and loss. In addition, they protect roofing
membranes against ultraviolet radiation, extreme
temperature fluctuations and puncture or other physical
damage, significantly increasing a building’s system's
life expectancy.
So a green roof eventually
pays for itself, while you
enjoy.

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