when should old paint be removed from drywall?

I'm getting ready to paint a room. I was just pulling out an old cracked window stool when I noticed that the paint around the window would peel off very easily in six to eight inch strips. I probably wouldn't have noticed if I hadn't been removing the trim. Should I be pulling all of this off the wall before I paint? I've read that loose paint should be removed, but "loose" seems to be indistinct. It's not peeling, or anything, but if I slip a scraper under an edge, it glides under the paint.
Some of it is more firmly attached, though if I'm a bit more persistent it will come up, too. Am I just making more work for myself?
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You're right - the term "loose" is very general. The definition can be bent by various factors:
1) Is your perfectionist spouse watching? 2) Is there something else you'd rather be doing, like fishing? 3) Do you have sandpaper and a container of spackle handy, for evening out the now-uneven surface? 4) Are you painting because you're having guests? Tomorrow? And you knew about this a month ago, but now it needs to be done today?
Seriously, press gently on the paint. If it feels like it hasn't separated, patch & sand as necessary and paint over it. The ability to get under the old paint with a scraper isn't a good way to decide, since you can get under lots of good paint that doesn't need to be removed.
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snipped-for-privacy@thecraftstudio.com wrote:

Isn't that what home improvement is all about? Making more work for yourself? ;)
It sounds like someone painted over gloss or semi-gloss paint and didn't bother to sand the surface prior to painting with the new paint. This is particularly egregious with latex paint over oil-based paint.
Removing all of the paint would be a very big job and a major pain in the ass. If the paint is separating between two older layers of paint, not between the most recent paint you will be painting over and the old stuff, you can probably go right over it after prep work. That would entail, scraping off the obviously loose stuff, sanding the edges so they're not sharp and sanding the newly exposed older paint surface to give it some "tooth" that the new paint can adhere to. From there I usually use Benjamin Moore's Frest Start primer to coat the newly sanded areas. You particularly want to make sure that you are brushing towards the undisturbed paint so that the primer is pushed into the edge between the two paint layers in question. This will help bond the layers together. Then I would use a patching/spackling compound like Ready Patch to smooth out any imperfections. Lightly sand, another quick coat of primer on the patches and then you're good to go with your finish paint.
R
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peel and scrape as need, rough up area, prime with bin or kilz for better adhesion, use spacle or drywall mud to feather edge, drywall mud much easier to use.
clean and prime again then paint
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