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The upper structures of the State Library are currently being restored and there’s no surprises as to why the work is necessary – water ingress in various forms! A vital component of the overall work is to guarantee leakage mitigation, making Flex A Seal’s participation particularly significant.

The large, octagon-shaped, dome roof was replaced 20 years ago, with the surrounding gutters replaced with Rheinzink (titanium zinc) at the same time. This installation has been mostly successful. The exception is the gutter construction: insufficient allowance for thermal movement led to ruptures of the gutter structure joints, resulting in leaks that have affected interiors beneath the dome.

This problem was compounded by the dwarf parapet wall built in front of the gutter, designed to prevent flood water from overflowing onto the roofs below during torrential storms. Despite in-built overflows within the parapet (of which there were too few), water would fill the gutters and flood the underside of the roof space during storms, with the parapet acting as containment.

In charge of the project are specialist heritage architects Lovell-Chen, who elected to line the gutters with a PVC sheet membrane system. Wolfin waterproofing membrane system was chosen through a selection process with Flex A Seal Pty Ltd contracted for installation.

The advantage of installing Wolfin PVC membrane system was that it could be done as a retrofit directly onto the Rheinzink gutters without disruptive co-procedures involving removal of any part of the main dome roof. The membrane is also flexible and sturdy enough to cope easily with the prevailing structural and atmospheric conditions.

Flex A Seal’s precondition for winning the tender was that a flexible and effective installation design method to be worked out. The builder (HBS Group) and architect had previously agreed to remove the dwarf parapet as an obvious design improvement (see photos #2 and #3). However, even after the removal of the parapet, there was limited space and careful stage-by-stage planning was needed. The job required a combination of preassembled and in situ installed membrane and flashing components, as well as progressive quality control checks.

Our collaboration with the builder’s site manager made it possible for our staff to work in optimal conditions, making our role both interesting and worthwhile.