Green Roofs - Living Architecture Monitor - Fall 2016 - 13

growing media erosion, media
depths remain as intended and
plants have the necessary depth
and nutrients to thrive. By
keeping components in place,
edging allows the membrane to
last longer without being worn
by abrasion. If an edging material
absorbs heat, such as a dark plastic material, it could cause plants
in close proximity to it to die off.
LAM: What are some important
features of good edging systems?
AC: The most important
feature of a quality green
roof edging system is that
the edging be constructed of
a heavy-duty 100% recycled
material. Black rigid polyvinyl chloride (PVC); carbon
black concentrate; and impact
modifier green roof edging
will help to achieve LEED
points and is available in flexible or rigid styles to suit the
design. PVC edging is easy to
install and does not require
cutting or snipping to make
curves. Also important are
interior vertical wall 1.375"
drainage slots that can effectively manage water runoff.

DM: Systems must be lightweight to lessen structural loads and
able to withstand extreme temperature variations without damaging, as well as allowing for the free flow of water to avoid trapped
water on the membrane. On many green roofs, aesthetics become
important, as the edging can be visible to users of the rooftop space,
so edging that offers aesthetic details work best in these scenarios.
Finally, it is important that any edging resting on the membrane does
not have edges that might puncture it, which is easily achieved by
using edging that is specifically engineered for rooftop use, instead of
simply fabricating bent sheet metal.
LAM: What recommendations do you have for designers when choosing
edging/restraint systems?
AC: Talk to an edging specialist and explain your specific design
needs. Ask the edging manufacturer to send you samples so that
you can check out the durability, flexibility and/or rigidness of the
edging product's construction. Think outside the box. Don't go with
an edging product you've always used. Try something different. You
just may really like the results. Also make sure that the manufacturer
backs their product with a guarantee. The edging should be guaranteed to last 20 years or the lifetime of your project
DM: Choose edging that does not limit your design process. So
many green roofs are a series of rectilinear lines, yet the majority of
ground landscapes are curvilinear. Edging products should match
your design instead of limiting it, so work with a company that has
expertise in edging and is able to offer solutions. Many times edging
is the last thing considered, and often the first thing compromised
when budget considerations arise. It's important to remember that
your design is created by a series of lines, and they are important to
maintain for a project to look as good in its tenth year as it does on
its first day.
Blaine Stand is the Membership Coordinator at Green Roofs for Healthy Cities.

Photo courtesy of Oly-Ola.

quality edging is used, the crisp
lines of a green roof design are
held strong, and the visual appeal to the human eye remains
intact. A low quality edging, or
an edging made of improper
material, will begin to curve or
warp over time, causing the lines
to look disjointed.
LAM: How do edging/restraint
systems affect green roof performance?
AC: A specially-designed
green roof edge restraint gives
a landscape designer the opportunity to create beautiful
roof gardens with truly appealing landscaping and alluring
design concepts. The edging
defines and separates planting
materials, stones and pavers in
green roof and living roof construction projects and allows a
designer to create roof gardens
designed to suit the specific
needs of the users.
DM: Edging is vital to the
long-term structural integrity of
a rooftop. When everything is
securely held in place the roof
will last longer, while requiring
less maintenance. By preventing

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