Polycarbonate skylights

[Hamish Lonsdale]

I almost made a terrible mistake today. We are replacing the old transparent fibreglass skylights in the workshop with new polycarbonate panels.

I thought you could use the old gal. self-tapping screws again, until I checked with the roofing supplier. Polycarbonate expands and contracts with temperature up to 10x as much as fibreglass, and needs holes to be drilled significantly larger than the fixing screw. There also has to be a sealing washer large enough to allow for the movement

It seems that all this technology is available if you only ask the right questions!

[pawnhead]

You can get screws with a toothed washer attached that cuts a clearance hole for the screw shank.

[Hamish Lonsdale]

Well that would save a lot of time pre-drilling the holes. Good one! Do they work though? I suppose you need a few years to find out.

[Pusser]

They work fine. I made a screen using the bunnings 10mm drill and jig which sits on the ridge. It worked but PITA two drills on the go. got wise when roofing a pergola - used the screws with built in cutters - one drill just like driving any hex head self tapper. Got them at Bunnings in the normal screw section.

[pawnhead]

I used standard roofing screws with no cutting washer for my laserlite pergola roof. No clearance hole. Just screwed straight through the laserlite and into the batten. It's been up for over a year now and I've had no problems. It doesn't creak at all, and there's no foam tape under it either.