Geosynthetics August/September 2022 - 16

Geosynthetics in green roofs
is extremely simple, it offers a better aesthetic
finish, the installation does not
require specialized labor, it generates
surface stability and erosion control, and
it minimizes the excess accumulation of
water, avoiding overweight.
of the aggregate, bulk density, internal
friction angle and cohesion.
Geotextiles on green rooftops can
FIGURE 4 (ABOVE) 6,598 square foot
(613 m2) extensive green roof for
meetings on a corporate building
FIGURE 5 (BELOW) 979 square foot (91
m2) intensive green roof on a residence
fulfill several functions such as serving
as anti-vegetative layers and preventing
the growth of unwanted weeds, and as
a protective layer of the geomembrane
against granular soils that could cause
damage to the geomembrane by punching.
They can also be used for vegetation
separation according to the terms of the
design. Geotextiles are versatile and flexible;
they can adapt to the irregularities of
the surfaces on which they are installed.
Geocells
Geocells are usually used on roofs when
the slabs have a slope greater than 15
and up to 60 degrees, since they can confine
the filling material, performing as a
surface erosion control system. The best
performance from geocells is achieved on
gabled roofs or when the design involves
volumes on the roofs for a natural effect
or an organic design. They also allow
hydroseeding, protecting the roots.
Using this system provides several
benefits, beyond the reduction of costs
and installation work time, compared to
other types of systems. Its transportation
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Geosynthetics | August September 2022
Geogrids
Geogrids can be used in green roofs
as soil reinforcement to improve their
mechanical properties, especially in cases
when the substrate layer is thick, since
geogrids have openings that allow an
adequate interlock between the soil particles
and the geogrid. Their resistance to
stresses and to biological and chemical
conditions of the soils makes geogrids the
best option for these cases.
Regarding placement, these are
tended horizontally between layers of
soil in order to form an embankment or
redistribution of the loads on the structure,
absorbing the stresses that the soil
does not take.
Installation of geosynthetics
on green roofs
1. Preparation of the cover
It is important to take the following
into account before starting any type of
procedure or placement of any material:
¶ Although the geomembrane will
act as a waterproofing system, it
is recommended that the area has
a traditional waterproof system
prior to installation. This is to prevent
direct condensation on the
slab from the thermal gradient.
¶ The slope on the surface has to be
at least 2%.
¶ At least one 4-inch (10 cm) diameter
rainwater runoff is required
every 538 square feet (50 m2).
2. Geomembrane placement
The geomembrane is used as a waterproofing
and anti-root system, since it
has a high resistance to chemicals and
Geosynthetics August/September 2022

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