In April 2016 the Western Australia Building Commission published a comprehensive report on how well sheet metal roofs were being constructed in WA. The main reason for this report was an analysis of all wind damage in the metropolitan region which indicated because of the change in material and construction practice in Perth that many metal clad roofs do not meet the performance requirements as set out in the Australian Standards, Building Codes and National Construction Code.
The design and construction of a house with a metal clad roof must allow for wind 'up-lift' forces. This basically means that the design of the roof structure needs to allow for the roof to stay attached to the house structure where there is a high wind event like a significant storm or cyclone. In a conventional roof construction there are many timber joints where the rafters attach to the ridgeboard, rafters attach to the underpurlin and external wall plates, struts attach to the underpurlin and the wall plates or strutting beams and beams attach to wall plates. ALL of the joints need to meet certain 'up-lift' forces which usually means that these joints need a mechanical anchor or strapping.
The Building Commissions report revealed that many of the inspected roofs had not effectively linked together all the related tie down elements within the roof structure from the ridge down to the wall plates. The reasons for this came down to a lack of understanding of the Australian Standards and requirements of the building code by the relevant trades. Additionally there was a lack of documentation by the builder and engineers to clearly show details on how to meet the applicable performance standards. There was also a lack of or ineffective supervision by the builder to sufficiently focus on the key components of the buildings roof. Also, the permit authoritys (local council) monitoring, investigation and enforcing of compliance with applicable building standards was shown to be ineffective.
The Building Commission inspected 123 houses throughout the perth metropolitan area and in the south west as part of their investigation of this issue. Out of those homes they found that only two homes were found to be satisfactory across all the relevant inspection points. They found that 14 of these houses had zero satisfactory relevant inspection points!
What does this mean for you the home owner? If you have a metal clad roof on your home it is very likely that it does not meet the criteria as set out in the Building Code or relevant construction standards. Perth Property Inspections can inspect your home with these standards and inform you of any non compliance issues that may be present in the roof structure. The usual course of action from then if problems are identifiend is to contact the builder and inform them of the issues, they should then inspect the structure and provide an engineers letter if they believe it has been done correctly or they need to complete work to make sure the structure complies.
For further advice call Perth Property Inspections on our free call number 1800 781 251 or check out our website at Perth Property Inspections