Submitted by Cychotical t3_12667pz in DIY
As the title says. We bought a house and in several rooms I noticed the most recent coat of paint easily scratches off with your fingernail or a taping knife. We do want to repaint the whole house. But wanted to know if we need to do any special prep to prevent the new paint easily coming off with the old paint.
Edit. Thanks everyone. Looks like I will be scraping it off, cleaning, and priming it properly.
It's probably latex over oil. You have to get the latex off, and then either prime the oil or cover it with more oil paint. Big Box stores no longer sell oil based paint.
Latex paints work fine over oil-based paints, as water-based coatings work just fine over oil-based ones once they are fully cured.
If the existing coating happens to be very glossy, there can be adhesion problems, but oil-based does not inherently imply glossy.
For long-term adhesion one should use an orbital sander on the oil paint, then wash the surface with a TSP solution, and then use a latex paint primer. Only after these steps are taken should you apply two coats of latex paint. It’s a pain in the ass that uses more materials, but it can be done. It’s about the same amount of work as just stripping and repainting with latex from the wall up
Not understanding your comment. My mother had latex paint on top of oil paint, and the latex paint peeled off. I would not recommend that anyone do this.
My point is this is anecdotal. There's nothing inherently wrong with using water-based paints over oil-based ones. If you do the work properly, and apply the principles of good painting prep, it works just fine.
My time in the Home Depot paint department has shown that people do not follow the principles of good paint prep haha
SOME latex paints are ok over alkyd(oil). Typically higher end, 100% acrylic latex paints are recommended. SOME latex primers are available for oil to latex conversion also. Not all primers will do this
Were people painting walls with oil based paint in the 80s?
Paints were transitioning then.
First off, is the old paint lead?
1981 house in the US. I did check several layers of paint for lead in a different room and no issues. But I can check the specific rooms with this issue later.
If it’s 1981 you’re probably good and it’s actually pretty evident whether it’s lead by cracking patterns (I’ve done a lot of abatement projects).
That being said, trust but verify and always check places like basements, etc.
Cheaper to get it done whilst you have your contractor there already
You really probably have to peel anything off you can, skim coat the areas that pulled off with mud and prime the whole wall. Someone else mentioned stix which imo is the best primer. You could also use all prime which is a clear primer that works well on drywall where the paper has come off leaving a rough brown texture. If you mud over that without using all prime your mud is likely to crack and bubble.
You're referring to the trim paint? It wasn't prepped properly and unfortunately you'd have to scrape it all off and start again.
Oh unfortunately it’s the whole wall… of several rooms
That's not good. Pick up some wide carbide scrapers and some Stix bonding primer.
Stix is the best, especially for cabinets or other overpaint items.
Get rid of the old paint first
Someone applied Latex paint over oil paint.
Latex paint typically will not stick well.to oil paint. If you paint Latex over oil, it will peal off. It can be done, but there is a process. Definitely requires a prep and then applying a coat of fresh start primer on top of the oil paint and then Latex on top of that..
Scrape or sand or https://www.wagnerspraytech.com/products/surface-prep-tools/paint-eater/
Firstly, are the affected walls external to the dwelling?
Secondly, if the affected walls are external, are they a) stone, b) damp?
Plaster/drywall makes no difference as it’s hydroscopic.
The damp in this case, inhibits the paint’s ability to adhere.
Personally, I wouldn’t paint these kinda walls, I’d figure out a different use/approach.
Get a small piece of cotton fabric in a contrasting color fabric. Wet fabric with rubbing alcohol and rub the paint . If the fabric picks up the wall color, it is latex paint.
You can use acetone as well, as the effect is stronger. It will begin to neutralize the plasticizers found in latex paint, but will leave alkyd paints intact. Running acetone over the surface of a latex paint will cause it to develop a tacky texture that prevents sliding your fingers over it smoothly, always use non-plasticine gloves for a touch test
I've just had a similar issue on some doors. Real pain in the arse to get a nice finish with hard edges where the paint has flaked.
Agree with others who've said scrape as much if the loose paint away, skim with mud and reprime/paint
Latex over oil
I've battled this in our house every room I remodel. The original oil based primer coat has deteriorated and if you disturb the paint at all, like update molding or strip and repaint baseboard radiators, it chips off all the way to the primer layer. Some rooms have 6-7 layers of paint. My house was built in 56 and I've tested for lead every room in the house, no lead. But the issue makes it easy to scrap off all the paint, sort of. Then I clean, skim coat, sand, clean and apply a new coat of primer before repainting with color. I usually screw down the drywall too and spackle those holes, since I've had a lot of nails pop. It's a huge PITA, but the results are worth it I think. The walls look way better without the orange peel texture of 6 layers of paint and I don't have the chipping and nail popping problem.
TLDR strip walls, fix defects, sand prime paint
--Ty-- t1_je83wge wrote
There's a few different causes for this problem -- the most common is walls that are oily because of an air-based oil, like is often found in a kitchen, or because they put paint directly over a very smooth, very glossy finish with no prep. If it's across the WHOLE HOUSE, though, in multiple rooms, then these reasons don't really apply, and I suspect there was a systemic problem -- the painters let the paint freeze or expire, there was something like ceiling popcorn removal done throughout the house which coated the walls in drywall dust that wasn't removed, etc.
In any case, unfortunately, you have to remove all of the loose paint. I don't even know how that would be doable without tremendous cost, but if you just bought the place, it's something you can claim from the sellers as a deficiency.