Planning considerations - Living Roofs in Integrated Urban Water Systems - page 52

• How construction cost are changing during all the stages from planning to
construction - e.g., the estimated construction cost and ongoing and long-
term maintenance cost.
• How construction monitoring is taking place, with emphasis on assuring that
waterprooing isn't compromised during construction, and materials are
delivered as speciied.
3.2.1.2 Formulation of the design contracts
When the design consultant team is established, contracts between the client
and the design consultants are made. The contracts state the responsibilities of
each professional for their allotted task. In many cases, one consultant acts as
lead (often the architect), and is responsible for subcontracting the other profes-
sionals, and is also the primary point of contact with the client, in both the
design and construction phases of the project. The client must understand that
the project lead acts on the client's behalf to coordinate and oversee planning,
construction, maintenance and contract formulation. Alternatively, the client may
contract all consultants individually, in which case all consultants report directly to
him or her. In each scenario, speciic responsibility for who designs which part of
the roof assembly must be allocated. Depending on the scenario, it is the respon-
sibility of the lead consultant or client to hire other design consultants, such as
structural engineers, envelope consultants, mechanical engineers, horticulturalists
and ecologists.
Contracts should also deine the liabilities and responsibilities of professionals
that will occur during the construction period. The deinition of responsibilities
will be more comprehensive when the speciications and construction drawing
package is issued, as these documents will give speciic instructions to the con-
tractor for construction. During living roof construction, it is common for the on-
site project manager, architect and landscape architect to take on overall
responsibility and liability. The engineers and any other design consultant
professionals involved must take responsibility for aspects included only in their
scope of work. In North America, living roof specialist contractors and companies
can deliver a complete living roof system, including the waterprooing membrane
and warranty for the whole assembly. In Europe, living roof companies are
generally suppliers only to the landscape contractor building the living roof.
In terms of liability, one of the most crucial elements of the roof is the integrity
of the waterprooing membrane. The design team must deliver a watertight
assembly. In a retroit scenario, the architects, building envelope consultants and
specialty roof installers must assess the age and durability of the existing
membrane. Depending on its condition, it may require replacement. A
waterprooing membrane is more easily protected during construction with an
inverted roof assembly then with a warm roof assembly. The insulation loating
above the waterprooing membrane protects the membrane against sharp
objects during construction. A warm roof assembly (Sect. 3.3.3) is more sensitive
to sharp objects as the insulation is below the waterprooing. In this situation,