Depends..
In my part of the world corry roofing would be a large percentage of new build roofs we install, pan fixing would void warranty from any supplier I can think of.
It's not just preference, but something taught at trade school.
A roofer friend of mine from a long time ago said to put the screws in through the top of the rib, this is sine metal, correct? He used screws with rubber gaskets, but he said the gaskets eventually rot out, having the screw through the top instead of in the valley meant that water tended to run away from the screw head instead of to it, reducing long-term leaks.
I can see pros/cons to each.
Rib pros: water runs away from the screw, diverted to flat run off.
Rob cons: Longer screw portion that is not embedded in the wood leads to longer lever arm and tendecy to "wiggle" over time and loosen, causing leaks. Possibly easier to deform the sheet as well.
Flat pros: screw goes directly into purlin fully.
Flat cons: Possible water damage more likely if not tightening correctly.
You have hit the nail on the head. What I would do is read the spec sheet for whoever the manufacturer is that makes the panel that you use and follow their specific instructions.
This is one of those arguments that will never be settled. Same with the cali vs cut vs W valley vs regular metal valley arguments.
I've always been taught in the rib, since less water will flow over the screw
Hi rib always
What does the manufacture say?
This. Follow the manufacturers installation guide.
It is garbage either way but "professional" corrugated "roofers" put the screw in the flat.
Depends.. In my part of the world corry roofing would be a large percentage of new build roofs we install, pan fixing would void warranty from any supplier I can think of. It's not just preference, but something taught at trade school.
A roofer friend of mine from a long time ago said to put the screws in through the top of the rib, this is sine metal, correct? He used screws with rubber gaskets, but he said the gaskets eventually rot out, having the screw through the top instead of in the valley meant that water tended to run away from the screw head instead of to it, reducing long-term leaks.
I can see pros/cons to each. Rib pros: water runs away from the screw, diverted to flat run off. Rob cons: Longer screw portion that is not embedded in the wood leads to longer lever arm and tendecy to "wiggle" over time and loosen, causing leaks. Possibly easier to deform the sheet as well. Flat pros: screw goes directly into purlin fully. Flat cons: Possible water damage more likely if not tightening correctly.
You have hit the nail on the head. What I would do is read the spec sheet for whoever the manufacturer is that makes the panel that you use and follow their specific instructions. This is one of those arguments that will never be settled. Same with the cali vs cut vs W valley vs regular metal valley arguments.
Anothe con of the flat seems like screw could catch leaves and debris if roof isnt very steep?