AMI Australian Membrane Industries
The Sydney Fish Market roof is 10,500sm in size (14,500sm including the sheeting profile). The roof comprised of eight individual roofs separated by long and shallow box gutters. The roof was in a bad state of repair with numerous significant leaks and a lot of rusting and holes.
Cable tray rust (left) and general roof condition (right)
Rust holes and treatment (left) and bubbling (right)
The system employed saved the client in excess of $1.5m when compared to a total roof replacement cost. There was also no interruption to the operation of the Fish Market during the 4 month project. The system entailed repairing all roof sheeting fixtures and fittings, modifying the inadequate box gutters to cope with severe storm conditions, covering the roof with a thick urethane acrylic UV stable trafficable membrane (Ultra Flex) and finally, applying a top coat of a heat re-radiating membrane (Heat Block) to stop all heat from entering the roof/facility and to stop heat expansion of the metal roof structure thereby avoiding potential damage to the main membrane.
Syphonic drainage system
New horizontal downpipe system totalling 1,000 linear metres
The roof was over 40 years old, it has been previously patched and membrane coated. All previous repairs had not led to a long term leak free roof with absence of rusting and severe sheeting degradation. The previous membrane extensively bubbled and was peeling off.
The low roof pitch and extremely shallow box gutters had been incapable of removing the water on the roof quickly enough during heavy rain periods and this aspect caused additional damage and leaks. (due to the stramit panelling system below the roof line, leaks were difficult to locate)
Due to structural engineering issues, the box gutters were unable to be increased in depth or width, therefore a syphonic system was devised to rapidly take off water from the box gutters thereby enabling the existing box gutters to cope with the most severe storm conditions. The system was installed throughout the eight, 100metre long box gutters and increased the box gutter capacity to remove water by and additional 10 litres per second per syphonic system thus minimising the risk of water ingress into the building and potential maintenance problems.
Horizontal downpipes were fitted from the underside of the roof including the main auction centre, administration offices, and seafood school. These downpipes were connected to the existing down pipes at the top end of the pipes above the suspended ceiling, as the underground drainage system could not
be accessed. The installation was conducted out of working hours and avoided interruption to the function of over 20 different business operators that are based at the SFM, which is one of the busiest auction centres in the world.
Prior to the installation of the syphonic systems, the box gutters were stripped of their top rusted skins and a membrane system incorporating a polyurethane top coat was applied in order to minimise risk of corrosion due to pooling rain water and condensation.
Rusted box gutter skin removed
The sheeting profile has not been available for many years so replacement sheeting for those badly corroded areas was not available. In those areas and all holes/rust affected areas, the rust was treated and the damaged/rusted areas and numerous holes were fibreglass/membrane patched prior to the main coatings being applied.
137 smoke stacks on the roof proved to be a ready source of numerous serious leaks in particular rain/wind conditions. These were sealed byway of rapid curing class 111 latex membrane (Flowthane) impregnated with polypropylene fibres prior to been coated with the top coat membranes and urethane sealants. Over 500 metres of parapet wall cappings were removed and replaced with new colorbond metal capping. Numerous mobile phone towers were repaired with new flashings and decktites as the existing ones had perished from the continued exposure to water and bird droppings.
Numerous air-conditioning units of all sizes and cable trays, mostly supported on wooden supports which invariably had rotted through. New aluminium supports were installed under all equipment after the extensive rust in these areas was treated.
A combination of airborne pollutants (approx 60,000 cars per day pass directly over the fish market building) from motor vehicles, two cement works, salt laden water from the ocean, oils from food exhaust vents and extreme build up of condensation under cable trays created a very hostile environment which is particularly conducive to corrosion.
A rust converter was applied once the roof was pressure cleaned to expose all rust areas that were not evident on initial inspection. A waterbased two pack epoxy primer was used as a base coat before applying the Ultra Flex system with fibre reinforcement and the insulation membrane.
Rotting wood supports (left) and air conditioning units (right)
Left - New aluminium equipment supports. Right - Over 500 metres of new colorbond metal capping was installed
Once the roof was repaired and coating systems applied, it was critical that trades people going onto the roof to undertake maintenance to the plant there or mobile phone towers, did not walk on the roof membrane and damage the coating, therefore aluminium walkways were installed throughout the roof enabling access to all equipment without trafficking the membrane coating.
Membrane application via pressure pot system
The membranes employed were Ultra Flex (polyurethane/acrylic trafficable UV stable membrane) at
1.5mm dc and Heat Block, a heat re-radiating membrane designed to stop all heat transfer into the roof and underlying structure. The two additional advantages of Heat Block will be no sub structure movement due to heat expansion and a reduction in the air-conditioning power bills for the site.
A clear dust coat was applied over the heat re-radiating membrane to ensure that dust build up on the roof could easily be cleaned.
Finally a high content lanolin oil was applied around all areas where bird droppings were causing corrosion - the lanolin oil was chosen to prevent the acid in the droppings from rotting the metal roofing and gutters. A bird barrier was installed on all box gutters which also acts to stop leaves from causing blockages in the downpipes.
Some of the mobile phone towers on the roof
The project was completed on time and on budget - no accidents were reported and no disruption to business operations were experienced by the client Sydney Fish Market, Pyrmont. An ongoing maintenance program will ensure the integrity of the coating and plumbing system will be maintained.