# Skimcoating Painted Wall. Prime First?



## marcus118 (Dec 5, 2012)

I am going to apply a thin skim coat over a painted wall to smooth it out. My question is, do i need to apply any primer to the painted surface BEFORE i skim coat? 

thanks!


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## jeffnc (Apr 1, 2011)

No, you don't.


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## joecaption (Nov 30, 2011)

No way would I do it without real primer first.
It's no different then if it was all new drywall.


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## jeffnc (Apr 1, 2011)

Right, and you don't prime new drywall before putting joint compound on top of it.


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## ToolSeeker (Sep 19, 2012)

No primer needed before only after.


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## Sir MixAlot (Apr 4, 2008)

I like to hit a painted wall with a sanding sponge before I skim coat it. Probably not necessary. But. I feel it gives the wall a little more tooth and the sanding sponge only takes a couple of minutes. :thumbup:


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## Sir MixAlot (Apr 4, 2008)

^ Like this.


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## Nestor_Kelebay (Jun 17, 2008)

It stands to reason that if you roughen the paint, you have more surface area for the joint compound to stick to, and that gives better apparent adhesion.

But, by the same token, it could be argued that the OP should sand his paint before priming to get better adhesion of the primer to the paint too.

I don't think it's NECESSARY to sand or prime. It stands to reason that it should help, but I've never had a problem with joint compound not sticking well to unsanded and unprimed paint.


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## jeffnc (Apr 1, 2011)

I don't normally sand drywall or primer to get the next layer to adhere well, I do it to get a nice, smooth finish.


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## chrisn (Dec 23, 2007)

joecaption said:


> No way would I do it without real primer first.
> It's no different then if it was all new drywall.


That's why you are not a painter:laughing:


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## marcus118 (Dec 5, 2012)

thanks everyone! one other quick question. if i'm just applying a thin skim coat to smooth out the drywall from years of abuse, can i get away with one coat?


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## jeffnc (Apr 1, 2011)

Depends on how deep the holes are and how good you are at it! We can't say from here.


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## marcus118 (Dec 5, 2012)

jeffnc said:


> Depends on how deep the holes are and how good you are at it! We can't say from here.


I guess at a high level I'm looking to understand the purpose of multiple coats. I understand why you need multiple if you're skimming something like a textured wall or something very rough.

So at a high level my question is, if I know I want say a 1/8" coat, whats the difference between 1 coat that's 1/8" thick versus 2 coats each 1/16" thick?


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## jeffnc (Apr 1, 2011)

My reaction to that is that you're basically looking at it wrong 

It's not really possible to apply a skim coat of 1/8" over your entire wall. Even if you could, why would you want to? What you want to do is get a flat wall. There's not need for an extra layer of material on any areas of the wall that are already flat, and the majority of your wall is already flat.

What you're doing is putting a bunch of compound on the wall, then scraping it off with a flat trowel or knife of some type, leaving behind compound only in the depressions (whether they be holes, gouges, low spots, texture, whatever).

So the only question is, when the compound dries, will it shrink in those low spots enough so that you need another coat?

I use this basic technique, although I only do 1 coat. (If there's deeper damage, I'd fix that first by spot patching.) Skip step 1 unless there's much damage to the paper. The squeegee is more forgiving than a metal trowel.
http://www.familyhandyman.com/drywall/how-to-skim-coat-walls/view-all

So to answer your question, multiple coats is for people who:
- didn't patch the bigger gouges first
- couldn't get a smooth finish on the first pass


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## marcus118 (Dec 5, 2012)

jeffnc said:


> My reaction to that is that you're basically looking at it wrong
> 
> It's not really possible to apply a skim coat of 1/8" over your entire wall. Even if you could, why would you want to? What you want to do is get a flat wall. There's not need for an extra layer of material on any areas of the wall that are already flat, and the majority of your wall is already flat.
> 
> ...


ok that makes sense thanks.


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## blackjack (Oct 21, 2015)

marcus118 said:


> I am going to apply a thin skim coat over a painted wall to smooth it out. My question is, do i need to apply any primer to the painted surface BEFORE i skim coat?
> 
> thanks!


as long as the paint is stable (no chalking, peeling,etc., and it's not oil based enamel for some dumb reason like a bathroom wall or ceiling) just skim it. if the paint is failing at all, you're looking at a little more prep first. depending on a few things, i might "bomb can" fog (spray can of oil based primer) some areas first to give the mud something to bite to.


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## scottktmrider (Jul 1, 2012)

joecaption said:


> No way would I do it without real primer first.
> It's no different then if it was all new drywall.


why would you post a reply that everyone is disagreeing with than not defend yourself?


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## chrisn (Dec 23, 2007)

scottktmrider said:


> why would you post a reply that everyone is disagreeing with than not defend yourself?


he is not a painter


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## 78Vette (Nov 25, 2009)

If the walls are clean (none smokers) and flat-very low sheen, i wouldn't bother priming and go with a quick scuff. Any other scenarios get a coat of Glidden's "Gripper".


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