I am finding in a significant number of staged construction inspections that the roof sheet is being overlapped inappropriately in that the installer is paying little attention to the wind direction and how it might impact on the completed installation.

Interestingly the relevant Australian Standard, AS 1562.1- Design and installation of sheet roof and wall cladding, whilst referencing this does not make it mandatory. They refer it back to the manufacturer’s recommendations.

Note 2 under clause 4.4 states Consideration should be given to laying the initial sheet at the leeward end of the building, so the side laps are protected from the worst anticipated weather”.

Great advice but that is all it is, advice. The Code does not make is mandatory.

So what do the manufacturers say?

corrugated roof overlapChecking the two biggest manufacturers in South Australia we find that Stratco demonstrate diagrammatically laying in keeping with the suggestion in the code in their CGI Corrugated Brochure. Fielders in their Typical Pierce Fix Installation Guide state in note 4 that Sheets should be laid with overlaps facing away from the prevailing weather.

So why don’t roof installers follow these guidelines or principles? I can’t answer that question.


Next question is will the manufacturer guarantee their product if installed other than as suggested in these various publications? I fear not.

If you find this on your house I suggest you ask the manufacturer whether they are happy to guarantee their product as installed. This is all I can do on projects where I find it has occurred because while it is so easy for the builder/roofer to comply it is not mandatory and it is extremely expensive to correct.