How to fix polycarbonate roof leaking around screws?

Biscuit

Hi all, we recently installed a pergola and have added a polycarbonate roof with the greca profile at a 5° pitch. We closely followed the manufacturers instructions, but have found it leaks like a sieve. The issue is the water is running down the top of the ridge in rivulets and flowing in around the screws (pic attached). Any ideas on how to fix this? 

Our current plan is to add a line of silicone across the ridge above each screw to divert the water but would love ideas from anyone who has dealt with this before.

JacobZ

Hi @Biscuit,

A warm welcome to the Bunnings Workshop community and thank you for your question about a leaking polycarbonate roof.

Your thinking is sound and is definitely in the right direction.

What type of screws did you use? 

If you've used screws like these Polydome 12G x 50mm Polycarbonate Roofing Screws with a rubber washer, overdriving them can cause the rubber washer to split which will allow water to get through. They should be driven so the screw lightly purses the washer. If the washers have been damaged in the installation process, replacing the screws is worthwhile.

Adding silicone on top of the polycarbonate sheeting can also help, but you are much better putting it in the locations where the water is getting through than on top of the ridges. Locating the points where the water is getting through like where the sheets overlap, or the screw holes and applying silicone there will prove much more effective. You can back the screws out slightly, add a daub of silicone and then drive them back in to help seal around the screw penetration. Use a high-quality translucent silicone such as Selleys Translucent Roof And Gutter Silicone Sealant.

Let me know what you think and if you have any further questions, please don't hesitate to ask.

Jacob