Painting Over Latex Paint in a Garage
#11
LOML has decided we need to repaint the garage.  Right now it's a horrid foam green that's left over from the previous owners.  

I was going to do a skim coat of mud over it because it's a garage, there's some damage to the walls.  Damage that was painted over previously.  

While trying to knock off some loose stuff in preparation for the skim coat, I happened upon a bubble in the wall.  I picked the bubble and kept peeling and the next thing you know I've got a few square yards of bare drywall where paint used to be.  

So some of the paint is stuck on and doesn't scrape off at all.  While others is peeling off in sheets.  Do I scrape it all back down to drywall to ensure I don't have any problems?  Do I leave what seems to be adhered well?  

What of paint will work best over the current latex?  We're going with a white color, so I'm planning on doing two coats.  

Any advise before I proceed?
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#12
If it were me, I'd leave what is sticking and paint over it. I would prime everything though (even the old paint) before putting up the new color coats...besides I doubt 2 coats of white would cover the green anyway. So the primer will some help covering the old paint. As for type of paint, a lot of wall paints anymore are 100% acrylic resin, and I really like them compared to the older latex paints. Just stay with one of the good quality paint companies and I think you'll be fine.
I started with absolutely nothing. Now, thanks to years of hard work, careful planning, and perseverance, I find I still have most of it left.
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#13
I'd try and find out what made the paint peel off. Maybe it is moisture due to no insulation/vapor barrier? Perhaps because it isn't climate controlled- expansion/contraction/moisture? Depends a lot in what your climate is and that's what garages do? This may determain if the mud holds up.

I'd remove every bit that is loose and use a good primer before mudding and painting with good quality latex.
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#14
I generally agree with Fredhargis and daddo. I have gotten really good results using Zinnser's BIN primer; particularly where there are difficult adhesion problems. It is a shellac based product and sticks to most anything and most anything sticks to it. The area where the old paint is bubbling off will likely benefit from a coat of BIN, but you can also prime all the rest with it as well, including any mud repairs.
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#15
After more scraping this morning, it seems that the worst spots are in fact where an area was mudded. And, to top it off, this is on an exterior wall that I would guess has no insulation.

The bad spots that I was initially going to fill in turn out to be places where the paint peeled off before and was painted over (poorly).

Am I asking for trouble by putting more mud on this wall? The wall seems dry. No moisture spots at all. I noticed the old mud seemed kind of porous and light. I could make the dust fly just rubbing my hand over it.
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#16
If the existing paint is oil, then you will have to prime first. Zinzer water based cover stain is a great primer for interior or exterior. The only reason to use oil primer is if you have very bad stains or want to do some nice woodwork and sand between coats to get it very smooth.

You could use an exterior water based acrylic paint for inside the garage, since it isn't climate controlled and it will get more use than the inside of a building. Around here, oil is a pain to find and pointless, for that type of work.

Use a decent quality paint like in this review https://10carbest.com/best-paint-for-garage-walls as it covers better and is easier to work with. My go to paint is Behr (home depot) premium plus or ultra premium plus and they run 28-38 bucks per gallon. The ultra, which is supposed to be primer and paint in one, is a joke for the most part. It may stick better than the pp, but I will not rely on it as a primer. I have used many brands and many many thousands of gallons of paint over 20 years, and the Behr was convenient to get and it turns out great. It is more about the prep work and skills of the painter than it is the paint, as long as you don't use paint that is total crap
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#17
(06-30-2018, 12:45 PM)DieselDennis Wrote: After more scraping this morning, it seems that the worst spots are in fact where an area was mudded. And, to top it off, this is on an exterior wall that I would guess has no insulation.

The bad spots that I was initially going to fill in turn out to be places where the paint peeled off before and was painted over (poorly).

Am I asking for trouble by putting more mud on this wall?  The wall seems dry. No moisture spots at all.  I noticed the old mud seemed kind of porous and light.  I could make the dust fly just rubbing my hand over it.

Since it is in the area of where it was mudded, it was probably not cleaned of drywall dust before painting.  Clean it off with a damp sponge or cloth before priming.  Roly
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#18
They may have used the wrong kind of mud when they patched it. You will probably never know.
Scrape off what is loose. Patch. Primer. Paint. As stated earlier. The Zinnser BIN primer is good
stuff. The paint is the easy part, as you know. The prep work is where the project REALLY is.
Mark Singleton

Bene vivendo est optimum vindictae


The Laws of Physics do not care about your Politics   -  Me
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#19
You really need to primer.  Whoever painted did not, that's why its peeling off.

You can use the primer made for drywall on the bare spots, but I would prime everything.

+1 on the BIN shellac based primer.
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#20
When I redid our hall bath, I knew I was going to use gloss latex. So, I primed with a PVA(drywall specific) primer. Problem with that was the gloss looked horrible. So, I reprimed with shellac based BIN.

I know you don't intend on using gloss, but the BIN is something I have used over almost every wall surface with zero problems. As long as you have dealt with all the loose old coatings, the BIN will be the best primer.
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