Will the wood of this overhead rot if it is not painted?
 

Does this overhead need to be painted? Will the wood rot if it is not painted?



Thanks.

Depends on what type of wood it is.
However, if it's already painted as it appears, a coat of primer and outdoor paint certainly won't hurt it.

It could possibly rot, but who knows. It looks like it needs to be painted

Definitely needs paint. But only after a lot of proper surface preparation (as in removing any/all loose or potentially loose existing paint). Otherwise, you're wasting your time.

1. What happens if all the paint is not sanded off before new paint is applied? Will the paint just come off?

Yes the paint will peel right off, save your time and money, unless you are prepared to properly prep and paint.

What in the world is it?
If that was suppost to be some kind of pergala, the boards are way to close together and will be near imposible to sand and paint properly, there also way undersized.
If there pressure treated paints not going to stay stuck to them. It should have been allowed to dry out then soild stained not painted.
Any job is 90% prep work for good results. There is no magic wand or "special coating" to cover up peeling up paint.

If it is cedar it should not be painted , cedar will last if it can dry out. That may be a solid color stain that is on it.

...looks like a fiberglass cover(upper left in picture) either has been covering the wood or is planned to be used to cover the wood. If this cover is used might get by w/o painting the top for a while. Scraping looks to be challenging. Maybe a good coat of sherwin- williams duration high gloss might bide some time, especially if covered w/ the panels.

Or just plant trailing plants that will entwine all throughout the structure and go as long as you can w/ the natural look. Knowing one day all will have to be torn down and replaced eventually. That might bide you 10+ years.

What do you mean by the boards are "undersized" undersized how? This was painted somewhere around 6-7 yrs ago. Does this look like it should after that period of time in the sun OR was it likely not sanded and prepped properly last time?

Thanks.