Prime and paint fascia before or after hanging?

Question

I'm replacing a couple pieces of wooden fascia that have partially rotted, but am a bit unclear on the order of operations for successful water/rot resistance. The boards will be a couple lengths of 1x6 that will be nailed up, and one section will have a length of gutter (re-)attached. Some sources (e.g. YouTube) suggest priming and painting before hanging, and then it's done. But wouldn't the nails be an entry point for moisture (rain, melting snow/ice)? Is it fine to prime+paint before nailing the boards up? Or should they be primed and painted in-place after hanging, to cover the nails? If they can be painted first, is additional sealing/protection needed for the nails?

Answer 1

Outside wood should be protected as much as possible.

Nailing it up and then priming and painting only protects the faces you can get to, usually the front and bottom face/edge.

Prime and paint before putting it up, gives you the chance to prime and paint all faces/edges to seal the the wood from moisture.

Any nails should also be painted after for better sealing.