Do you fix through the crown or the valley of a corrugated sheet?
Fix through the crown, the raised top of each corrugation. That keeps the fixing on the high point where water runs off, so the sealed cap has the best chance of staying dry.
Are these for plastic or metal corrugated sheets?
They are made for plastic corrugated sheets such as PVC, polycarbonate and bitumen, fixed to timber. For metal profile sheets you usually want self-drilling roofing screws with a washer instead.
How many fixings do I need per sheet?
As a rough guide, fix through the crown at every purlin and space the fixings across the sheet width so it cannot lift. Patterns vary with span and exposure, so follow the sheet manufacturer's fixing guidance for your roof.
Do the caps actually stop leaks?
The hinged cap snaps over the screw head and presses down to seal that point against water ingress. Fixing through the crown and not overtightening the sheet both help keep it watertight.
What colour options are there?
This version has a black cap. TIMCO also make the same fixing with a clear cap, so you can match the fixing to the sheet colour.
What size are they and how are they sold?
They come in sizes such as 10 x 3 inch and are supplied in bags, for example 50 per bag. Check the size against your sheet thickness and the depth of your timber.
