How to remove Onduline roofing nails?
They are ring-shank nails, so they are hard to pull by design.
You need a crow-bar, pry-bar, ripping bar, wrecking bar. Solid steel with the &quot;claw&quot; on a looped end, 2 or 3 feet long. Not a hammer. Apologize to your hammer if you haven't already wrecked it.
Preferable to leave the heads on, as it will be faster to rip them out with the bar if you don't have to put mole grips on each time, and take them off, and not impale yourself on a bunch of cut-off nails in the meantime. You can probably rip the glorified tar-paper roof off around them if you'd rather have it gone when you are removing the nails.
I have (the remains of) an Onduline roof I put on 20 years ago. I will be replacing it with metal - that was an experiment that has results I won't be repeating. The metal roofs I put on at the same time are in excellent shape.