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Discussion Starter #1
I've got new drywall in a room where I'm keeping the drywall on the ceiling and one of the walls - both the ceiling and old wall need to be painted when I paint the new drywall.

To fill gaps between walls and between wall and ceiling where things weren't perfectly square, I'm planning on using EasySand 90 setting type compound. Do I need to sand the painted wall and ceiling before filling gaps? If yes, just lightly scuffing the paint or deeper sanding?

Does it matter whether the paint is latex or oil-based, meaning can I apply compound to either when gap filling?
 

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JUSTA MEMBER
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The compound won't stick to the smooth paint, it needs TOOTH to hold to the painted surface.

So yes, sand fist, and run a test on a small spot first , before committing to applying compound to the entire thing.

If it sticks to the small area, it should stick to it all.

One thing that I have found, is where Tobacco stain is on paint, it is best to try to clean the stain, or paint over it all, because it does not stick well, and will look very odd afterwards.


ED
 

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retired painter
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A quick scuff sand with 80 or 120 grit should be sufficient. Walls get patched all the time with setting compounds without any big fuss.




IF there are nicotine stains on the old walls they should be coated with an oil base primer to insure they won't bleed thru the finish paint. Latex primer is fine for both the new drywall and the extra mud.
 

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Discussion Starter #4
A quick scuff sand with 80 or 120 grit should be sufficient. Walls get patched all the time with setting compounds without any big fuss.
Would something like 80 grit also be the correct grit to prep those painted walls/ceiling for primer?

IF there are nicotine stains on the old walls they should be coated with an oil base primer to insure they won't bleed thru the finish paint. Latex primer is fine for both the new drywall and the extra mud.
Wouldn't sanding the old walls knock off the stains, since I would assume nicotine stains sit on top of the paint?
 

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retired painter
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80 grit is a bit rough for the final sanding before paint and the sanding scratches might show thru.


I've never tried to sand off nicotine but I suspect it seeps in and doesn't just lay on top. I've always used a solvent based primer to seal the nicotine. It's quicker and more efficient when doing it for a living. I often scuff sand walls with 120 grit prior to painting.
 

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Questions

I've got new drywall in a room where I'm keeping the drywall on the ceiling and one of the walls - both the ceiling and old wall need to be painted when I paint the new drywall.

To fill gaps between walls and between wall and ceiling where things weren't perfectly square, I'm planning on using EasySand 90 setting type compound. Do I need to sand the painted wall and ceiling before filling gaps? If yes, just lightly scuffing the paint or deeper sanding?

Does it matter whether the paint is latex or oil-based, meaning can I apply compound to either when gap filling?
First off, what kind of paint is on the ceiling and walls? If flat, you probably don't need to sand first. If eggshell or higher sheen, then 120 should be good to use. If you use Durabond instead of Easy Sand it will be much harder and durable and will stick to almost anything compared to Easy Sand.

Secondly, is there nicotine from cigarette smoke on the ceiling and walls? If so, and if this were my house, I would go to a janitorial supply house and get cleaning chemicals specifically designed for cleaning cigarette smoke and nicotine off the walls first. If you prime first and the odor still outgases, it will be impossible to clean the odor causing materials as they are now covered by primer. A few years ago I cleaned the ceilings and walls in a ranch house where the owner was a heavy smoker - and you could really smell it! After cleaning the ceilings and walls with chemicals designed for smoke odor and nicotine removal....most of the odor was now gone.

Once you have all the sufaces cleaned, I would use BIN primer as that seems to have the best permiability rating of any of the primers out there, although I haven't checked in a couple of years. There might be some better primers out there at this point. If you do use BIN make sure that you buy it from a store that has a quick turn around in BIN sales as BIN has a shelf life that is printed on the can:

https://www.thepurplepaintedlady.com/2014/06/shellac-it-has-a-shelf-life/

siffleur
 
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