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Roddy Piper 08-24-2007 03:43 PM

Bubbling Paint - Re-do
I thought I could get away with painting a bedroom without primer - I was painting a diferent color over older latex that I had painted about 8 years ago. Well, all the walls went okay - except the exterior wall. I got small bubbles, which consisted not only of the coats I had put on, but the older coats as well! It was lifting it right off the plaster. WTF??? I should also mention that the upstairs of my house is very humid - its an older house and the AC doesn't cool the 2nd floor much (if at all). Anyway, I have begin stripping the paint off the exterior wall - most of it is coming off easily in strips (new coats plus older coats) with a scraper. What I plan on doing is putting a skim coat of joint compound on, then prime and paint.

What kind of primer should I use over the wall? I want to avoid a repeat of the bubbling paint. The paint itself is a latex maroon semi gloss (a name brand at Lowe's, can't remember brand).

Also, should I do anything to prepare the plaster wall? Underneath the coats of paint I am taking off is a thin coat of crumbly stuff - can't tell if it is the original paint or an old skim coat.

Also, should I wait until the humidity dies down? I'd like to get this done, but would rather wait if it will avoid the bubbling problem.

slickshift 08-24-2007 03:56 PM

Well, you shouldn't need primer for a re-paint
That's not your problem

If your new coat was lifting your old coat, it's more likely an old coat issue
That paint job was not prepped properly, or the wall was contaminated, or something else
It's just that the paint held until now

Usually in this sort of case, you can't just put joint compound on, that'll do the same thing
Usually you need to seal it first, with a problem solving primer/sealer, then j/c, then prime, then paint

You mention plaster...are the walls actually plaster?
How old are they?

Or did you mean sheetrock/drywall?

The crumbly stuff very well could be your problem
Is there paint or primer underneath that stuff?
Can you tell for sure if it's joint compound? or plaster?

Roddy Piper 08-24-2007 04:09 PM

Yes, the wall is plaster. The house was built in 1938. I can't tell if the crumbly stuff is a skim coat of plaster or old ugly paint (it is a tan color). I plan on sanding the wall with my random orbit hooked up to a shop vac at any rate.

So what kind of sealer would you recommend? an oil or water base - and is their a particular brand?

And you wouldn't recomment putting the j/c directly on the plaster, correct?

As for the primer, is kilz any good?

What is strange is that only the exterior wall (facing the outside) got the bubbles. I wonder if the heat and humidity has to do with it (I live in western PA).

I hate it when a 3 day project turns into a 3 week!

joewho 08-24-2007 11:33 PM

Old plaster walls don't have a moisture barrier and most likely all the insulation has sank to the bottom. Leaving in between the walls.

I suspect moisture. Make sure it's dry, dry, dry, surface and behind the wall before painting. The moisture problem will return, but if everything is dry when you paint, it should stick.

Short term solution is to get some venting to take the moist air out of there.

Roddy Piper 08-26-2007 12:18 AM

I guess the lesson here is to do good prep work. The original coat of paint that came pff with my new coat is the paint I put on when I bought the place 10 years ago - I was in a hurry with moving and all, and didn't do much prep work (actually I didn't do any at all:whistling2: ). The ugly yellow stuff is the original paint that that was on the walls. The outside wall is the only wall affected, so I plan on doing a good sanding, some crack patching (as I don't think I need a skim coat), then a seal and prime with Zinzer 1-2-3 before painting.

Someone mentioned that I should put the sealer/primer on BEFORE patching to create a moisture barrier - is this really necessary? I am worried that the joint compund won't adhere to the zinzer as well as it would the plaster itself.

slickshift 08-26-2007 10:08 AM

Absolutely Not True

Originally Posted by Roddy Piper (Post 59685)
I am worried that the joint compund won't adhere to the zinzer as well as it would the plaster itself.

This is an incorrect assumption
For repairs, it's always prime, j/c, prime, paint

Yes, the first prime is commonly left off because people have the same misconception you do...and many contractors are looking to save steps (time/money)
Yes, you can "get away with" not doing it sometimes and it'll be OK
But you are "getting away with it"

To insure the best repair, it's prime, repair, prime

Roddy Piper 08-26-2007 01:26 PM

OK - thanks for the advice! I don't want to do this again, so I will prime before patching.

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