Our neighbor across the street does this, too.Whenever we are doing work out front, the husband sits on their porch to watch us. When we were having new windows installed, he was watching. When we had the landscaping done, he was watching. New driveway, he was watching. New roof, he was watching. House painted, he was watching. Cleaning out the garage, he comes out to watch. Hurricane clean-up, he was watching. Hurricane preparations, he has to watch. If I wash my car in our driveway, he comes out to watch
This has been happening since 1997, when they bought their house.
This "habit" can be a blessing in disguise!!
The male half of the couple across the street from us is somewhat like your neighbor. Neither of us minds one bit, we just go about doing our "business", be it lawn mowing, gardening, what have you.
When upgrades are being done, I have no problem with him wanting to look, it's human nature to be curious!
The blessing part of this habit is that your neighbor most likely will know when or if a stranger is on your property.
We were not home when my father once stopped by to take photos of the front of our property, concentrating on our gardens.
Our neighbor stood in his driveway, watching my father, making no attempt to hide himself. After a few minutes, my father became aware of the fact that he was being watched, telling our neighbor at that point who he was.
Our neighbor then stated he knew we were not home and was worried that my father was up to no good.
Sometimes, what one perceives as nosiness is actually concern!