This large internal gutter (LIG) originally had a Nuralite bitumen sheet membrane on a chipboard substrate. When the gutter/roof started leaking the owner had a rubber membrane installed . The 1mm rubber was laid on new plywood fixed to battens, laid over the Nuralite and chipboard.
Because the fastening of the battens was into the chipboard and not into the framing the plywood lifted and caused further leaks within 5 years.
We lifted all the layers of the roof buildup down to the framing, the chipboard was taken away in big sacks, as it crumbled into wheatbix during removal.
New tapered firrings were installed to relevel the gutter, but the slope gain is restricted by the heights of the upstands under the metal roofing. We also widened the gutter outlet/scupper.
Here are some photos of the work.
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