Primer or undercoat or both

[woodman-46]

Hello,
When the weather gets better I will be working on our house's windows. Generally they are in good condition but I know there will be a few places that I might have to sand back to the bare wood. If so do I use primer just on the wood or does it matter if it overlaps/ goes onto the original painted surface around it by half an inch or so?
Sorry if this seems like a really basic question but would like to know.
Thanks

 

[Wayners]

Coverstain is a good primer for outside as it sticks to everything plus the other benefits.
Also will build out a bit and denib to a smooth surface with a gentle sand with 240grade.
Many primers if not all are primer undercoats. They will stick to old oil paints with the correct preparation plus prime bare wood.

You have to decide on what you want based on how bad is the surface.
You using oil or waterbased paints?
Rough outside wood I often used coverstain and left it a few days before I undercoated and glossed.
Example...
Coverstain
Dulux exterior undercoat
Dulux exterior gloss

 

[opps]

My go to, of many years, for exterior woodwork is oil based Dulux Trade Weathershield gloss. It used to have a solvent based (thin) primer/preservative. Once the primer became waterbased, I shifted to using waterbased primer/undercoat. I use the cheapo Leyland Trade acrylic primer/undercoat, followed by two coats of the DT weathershield oil based undercoat. If you feather the paint sufficiently, you will not see any step in the finish. I like the Leyland stuff because it sands back without clogging my abrasives.

 

[woodman-46]

Thanks for your advice . Much appreciated