Planning considerations - Living Roofs in Integrated Urban Water Systems - page 60

Figure 3.4
Protrusions and
perforations

300 mm

Gravel strip

AC.
BTC

Plant

Growing medium

Geotextile

Drainage layer

Waterproo ng membrane
integrated root barrier

Waterproo ng membrane

Mortar layer for leveling

Plant

Growing medium
Geotextile

Drain

Drainage layer

Waterproo ng membrane
integrated root barrier

3.3.3 Assembly design
A built-in-place assembly is typically designed by the architect, with input from the
envelope consultant, landscape architect, structural engineer and specialized living
roof installers. The assembly's component layers, and their order, thickness and
material density, are the foundation of the living roof and affect its performance
and visual success. In North America, most specialty living roof suppliers offer
minimum assembly criteria, which may be tailored to suit site-speciic conditions.
The assembly also inluences many important properties of the building below,
including its internal and external temperature, and acoustic insulation capabilities.
The functions and properties of the different layers inluence the thickness
and weight of the assembly. When designing the assembly, the design objective,
i.e., stormwater runoff reduction and plant survival, should determine the
selection of the different layers in the assembly. In the case of stormwater runoff
reduction, the assembly has to retain or detain precipitation levels depending on
the speciic climate where the living roof is located. The arrangement and the
properties of the different layers of the roof assembly will affect the amount and
duration of stormwater it can retain.
A roof assembly is characterized as either a “warm” or “inverted” (also
known as “cold”) roof ( Figure 3.5 ). The roof type is generally proposed by the