Planning considerations - Living Roofs in Integrated Urban Water Systems - page 62

Table 3.2 Living roof building element checklist for new roofs and retroits

Roof element Questions to ask Implication

Structure strength • Can the roof withstand both dead

(static) and live (dynamic) loads,
including water, vegetation, wind
uplift and people?

• Building structural integrity

Roof slope • Roof slope provides positive

drainage?
• What is the impact of differential
settling on low-slope roofs (if any)?

• Standing water can create a
structural burden
• Ability to drain water from the roof
by gravity may be compromised

Waterprooing • What is the quality and condition

of the waterproof membrane and
does it need to be replaced?
• How long is the warranty? (The
inancial implications of the
warranty may affect product
selection)

• Avoid water leakage
• Protect internal building from
moisture ingress

Perforations/protrusions/drainage
features

• Location and number of drainage
points and/or gutters?
• Ability to cluster perforations?
• Types? (e.g., air conditioning vents
versus machine room access)

• Waterprooing challenge
• Clear access for long-term
maintenance
• Random locations can compromise
aesthetics and increase costs of any
retrospective waterprooing

Maintenance access and rooftop
safety

• Physical access?
• Irrigation supply and operation (for
plant establishment or long-term
success)?
• Safety features to prevent need for
harnesses?
• Safe location for temporary storage
(plants, crates, rolls of drainage
mat, etc.), especially in areas with
higher load capacity?

• Costs of long-term maintenance
are related to health and safety,
and method of access
• Cost increases if specialist training
or access equipment is needed

Much of the success of a living roof lies with not only proper planning, but
also in a strong, comprehensive design of the elements that lie beneath the
assembly of the living roof. Table 3.2 presents a summary of important questions
to ask for each roof element below the assembly, and the immediate implication
of the roof element in the context of the entire living roof project.

3.4 PlanTs

There are many different notions of what is aesthetically acceptable to the
surrounding urban context, and this issue generates a great deal of discussion
among design and municipal review panels (Abrams 2009; greenroofs.org 2010).
Positive public perception has been shown to be more favorable towards carefully
designed living roofs presenting a variety of plant structures and colors (Fernandez-
Cañero et al. 2013). Sedum-dominated or mixed perennials also garnered favor
over grasses, which appeared “messy” (Jungels et al. 2013). Ultimately, the design