Hi Leon,
I was also caught out with a council sewer running through the back yard, was not highlighted in searches and is not deemed an easment, yet you cannot build near it 
Anyway good luck with the shed, whereabouts on the gold coast are you? I,m at Runaway Bay.
Cheers
Dave
Yep bloody council sewer mains!!!!! I too loose 4.5mtrs across the rear of my lot!!!! this equates to 14m2 smaller shed
