A quick guide to fixing latex paint over old oil finishes for beginners

I went through this exact nightmare in my hallway last summer. I thought I could get away with a quick scuff sand, but within two weeks, the latex was peeling off the door frames in long, rubbery strips. I ended up spending three days with a 2-inch stiff putty knife just to get back to a stable surface. It's soul-crushing work, expecially around the decorative molding.

I found that 120-grit wasn't quite enough for the old high-gloss trim. I had to drop down to 80-grit to relly break that glass-like finish, then smoothed it out with 150. I used Kilz Restoration instead of the Zinsser beacuse that’s what I had in the garage. It’s a water-based primer but it’s specifically meant for sealing in tough surfaces. It’s been six months and I haven't seen a single chip, even with the kids banging thier toys against the baseboards. Just make sure you don't skimp on the cleaning after sanding; I used a shop vac and then a denatured alcohol wipe to make sure there was zero residue left.

Man, I've been there. Next time, if you aren't 100% sure what the old paint is, rub a cotton ball with some denatured alcohol on it. If it doesn't rub off, you're dealing with oil. Also, if you're working on trim with alot of detail, check out a liquid deglosser. It won't save you from the scraping if it's allready peeling, but it's a lifesaver for getting the primer to bite into those tight spots where a sanding block won't fit. Just make sure you've got the windows open 'cause that stuff's pretty strong.

If you're struggling with those rubbery strips, grab a Wagner Furno 500. Keep it on a low setting so you don't cook the old oil layer, but it softens the latex just enugh to peel it off in sheets. If you leave those 'craters' where the paint didn't peel, you're going to see every edge under the new coat. I hit transition spots with MH Ready Patch before the final sand. For the re-prime, I swear by INSL-X Stix. It’s a high-adhesion waterborne urethane that bonds to almost anything. If it can handle my high-traffic garage entrance, it'll handle your hallway. Just wear a 3M 8210 mask—you don't want to be breathing that old oil dust.

If you really want that latex to stick this time, skip the hardware store brands and grab a gallon of Stix Waterborne Bonding Primer by INSL-X. I used it on my old oil-based kitchen cabinets after a light sand and nothing has even budged. It’s basically liquid glue for paint. It saves you from that nightmare of the paint sliding right off the oil sheen. Just give it 24 hours to really bite before you go back in with your topcoat.

Update: I’m finally thru the woods. That tip about using denatured alcohol for the test was a lifesaver for the rest of the house. I ended up using a heat gun on low to peel the rubbery strips as suggested, then went with the Stix primer. It bonded perfectly. My kitchen trim finally looks solid and isn't flaking off anymore!