It is hard to know if you will absolutely need to prime, but I definitely would do it. It will provide a much nicer finished product.

Sammie, can you elaborate on why it will be a nicer finish? I guess, I don't really know what primer is because I always thought it was used when you wanted to cover a dark color with a lighter one or a surface that had never been painted. Thanks.

I'm no pro, but I've remodeled several homes and done tons of painting - and almost always prime first. I think of primer as a prep coat to ensure that there is a smooth surface for the paint, and that the paint adheres well. I can't be sure, but I feel that primer also improves the durability of the top coat.

I doubt it. Why are you sanding? You can simply use TWO coats of satin finish paint, sand with fine grit, use a tack cloth after first coat to remove all possible grit............and apply a second coat!

If the door is heavily coated in a bad paint job on old wood doors?? Nothing but strip, prime and sand will do it.

A primer is not a substitute for two coats of paint. Remember.......latex paint can go over oil base. Oil needs a primer.

I sanded it because there were some drips and blobs from the previous painter. It sanded really well for an old, cheap door. Jan, are doors always satin finish if the trim is semi-gloss and they are both the same color or should the door be a different color. Hadn't thought of that? I know you said don't do it but I painted the hinges, came out ok!

Before during and after.

Thanks Mrs. S. I am going to go to the SW store.

The paint expert at Lowes didn't seem to have her finger on the pulse, if you will.

Now that you mention latex/oil, maybe I will just prime it. It's only 4 doors, not that big a deal.

I never use semi gloss on trim. I use satin. Plenty of soft luster unless you are living on a boat : ) Semi? Perfection of surface required...........: ( Every IM!!! perfection as seen in a magnifying glass. Just too shiny

Right about now I'd like to buy a boat and sail far, far away from this "it'll be fun to fix it up" crazy notion!

So no semi gloss, ok. So if the trim and door are the same color, both should be satin?

As long as it's not oil you are painting over, then you don't need to prime. But, primer is never really a bad idea. Also, satin and semi gloss is a personal preference thing but most people do use satin.

That’s old enough to have old oil based LEAD paint. I hope you tested it.

"IF YOU ARE GOING TO DISTURB LEAD-BASED PAINT FOLLOW THESE PRACTICES:

• Children and pregnant women must not do any lead paint removal work,
  and they should stay out of the work area until clean-up is complete.
  (See “Clean-Up.”) If you're not sure you can clean up every day, arrangements for temporary living quarters should be made.
• Work in one room at a time, and seal off the work area from the rest
  of the house, including any heating or ventilation ducts, using heavy
  plastic sheets (6-mil thickness).
• EVERYTHING in the room (furniture, rugs, carpets, floors, bedding,
  drapes, dishware, food, toys, etc.) must be removed, or covered with TWO
  sheets of plastic (6-mil) and all the seams taped. Plastic used to
  cover the floor should be secured to the wall or baseboard with duct
  tape.
• Wear disposable coveralls, shoes, hair covering, goggles and a properly fitting respirator.
• Only HEPA (High Efficiency Particulate Air) respirators will filter
  lead dust and fumes. Simple paper or fabric dust masks will NOT protect
  you from lead dust.
• To avoid ingesting lead, do not eat, drink or smoke while working.
• Clean up carefully. Before leaving the work area, dispose of
  coveralls, and remove dust from your clothes with a HEPA filtered vacuum
  cleaner. Shower as soon as you can, so you do not spread lead dust
  around your home or elsewhere."

Lead based paint was banned in 1978.

IMO priming is always a good idea so yes to the priming.I like a satin finish for both trim and the door.

Maybe call a pro? : ) It's not this hard. .........but if the paint is gloppy, gooey, badly done from earlier paint jobs you want to sand.prime,paint. Satin. Only you know the current state of the doors, and how picky you are for a good result

Man that hinge has lived a lot of lives if it’s only from the 80’s! They usually don’t get that buried by paint for a couple more decades.

If you have a poor dribbly gloppy paint job, whatever you put on top of it will show that mess through it. Sanding is a good move to fix that. Then prime with a shellac based primer, like BIN, to see what it its been sanded enough. Then your top coat.