When you’re spraying paint with an airless sprayer, you have to be able to do entire surfaces at one time to avoid lap marks. As this video from PaintLifeTV explains, you won’t necessarily see the lap marks right after the job is done, but over time they will become more visible because they weather differently.
Watch the video starting at 2:33 for the explanation of lap marks. At 6:22 Chris describes how they avoid lap marks when painting the second story.
The Technique
As Chris describes, you never want to stop your spray in the middle of the field. Instead, find things on the house to define horizontal areas. In this case there’s a vertical conduit of some kind. Windows and doors are good options.
If you’re working high up and you can’t divide the area into narrow enough sections to cover in one go, you’ll have to use multiple ladders or quickly move your ladder in order to keep your wet edge. Not easy!
More tips at https://www.idahopainter.com/