Old plaster that won't hold paint - Contractor Talk - Professional Construction and Remodeling Forum

hbiss · 07-26-2007, 03:23 PM

Ok, I gotta ask about this one more time here. Never seen anything like it and neither has any other pro that I asked over the years.

This happens to be my own house. It was built in 1955 and has gyp lath with a scratch coat and a finish coat of plaster over that. Pretty common around the NE in those days.

What I have never seen with any of the others is that any paint will start cracking and falling off after about 6 mos to a year right back to the bare plaster in many areas. When that starts you can take a single edge razor blade and peel the entire wall or ceiling back to the bare plaster. There is absolutely no adhesion in many areas, others just barely enough to hold paint. I have used alkyd primers, oil primers, alkali resistant primers, Binz and both alkyd and oil top coats. Makes no difference.

Kind of strange is that the plaster surface is very hard and shiney. I tried sanding to break the shine. Very hard to do because it's so hard but it made no difference anyway. The only thing that seems to work is to skim coat the entire bare plaster surface once you peel it with joint compound. I would rather gut or laminate new drywall than have to do that.

My theory is that this plaster is highly alkaline and any humidity or condensation on the backside in the walls or ceiling seeps through and actually creates an alkaline "paint remover" that breaks the paint bond. This seems to be borne out because the problem is at it worst on a ceiling below an unconditioned attic space. Any real moisture such as from a leak and of course the paint comes right off but with any plaster you can expect that.

Anybody seen this before?

-Hal

DeanV · 07-26-2007, 03:27 PM

try BM Calcamine (sp) Recoater. No promises, but I think that is what it is made for. Maybe call BM and check on that.

Riverside Paint · 07-26-2007, 04:33 PM

Yep, Ive seen it and at least from my experience there's not a whole lot you can do other than skimcoat the damaged areas.

In some cases, plasterweld will hold the loose stuff up, for a while. But its only a temporary fix.

plazaman · 07-26-2007, 04:33 PM

Hal ... i would say it the moisture causing the paint to fail. I just did a apartment rehab where you could tell the walls had moisture. I used a primer sealer and top coat x2 ... this isnt the real soulution, but it should hold for a while.

dougchips · 07-26-2007, 04:48 PM

Quote:

Originally Posted by DeanV

try BM Calcamine (sp) Recoater. No promises, but I think that is what it is made for. Maybe call BM and check on that.

Sounds like it. My sister had her place in RI painted this year and her ceilings had that type of plaster. The painter showed me how you can pull the wet paint off of the whole ceiling before it gets a chance to dry. Something about it getting wet and the bond can fail, like when you add a 2nd coat. If you roll it to much the bond will also fail.

Some of the RI painters on the site must be more familiar with this stuff. Her painter was very familiar with it and did not have an easy solution.

jackrabbit5 · 07-26-2007, 05:36 PM

Quote:

Originally Posted by hbiss

My theory is that this plaster is highly alkaline and any humidity or condensation on the backside in the walls or ceiling seeps through and actually creates an alkaline "paint remover" that breaks the paint bond.

It's called saponification. The alkaline in the plaster is reacting with the oil in the paint and making soap.

mdshunk · 07-26-2007, 05:42 PM

Quote:

Originally Posted by jackrabbit5

It's called saponification. The alkaline in the plaster is reacting with the oil in the paint and making soap.

I'm curious too, to know what the cure is? Acid wash the plaster, to neutralize the Ph of the surface, so that no saponification occurs?

hbiss · 07-26-2007, 05:54 PM

Actually I do remember washing down an area with muriatic. Didn't do anything either.

The alkaline in the plaster is reacting with the oil in the paint and making soap.

I believe you are right. The surface of the plaster after the paint peels has a kind of waxy feel.

-Hal

daArch · 07-26-2007, 07:33 PM

If the high pH is the the culprit, use latex (acrylic, naturally)Most latexes can adhere to a pH up to about 10. Although there are rumors of one (can't remember if it was a Zinsser or another) was being promoted to withstand a pH of 12. You can test for pH by numerous methods. BTW, I remember when we had a basement floor painted with an oil. It just never dried. That was saponification, basically the paint acts like it "reconstitutes". I have not heard of the "waxy feel".

If you think it is moisture, tape a piece of plastic over the offending area. In a day or so, you may see condensation on the wall side of the plastic - i.e. moisture problems.

If it is not the alkalinity or moisture, there may be some surface wax or other contaminant.

Was by chance this a highly polished Venetian plaster ? We've had talk about that in wallpaper forums because nothing seems to want to adhere to it.

OH, and BTW, plaster laid in '55 is not "old". It ain't even approaching old until it's lime on wood lath

Exroadog · 07-26-2007, 08:07 PM

Saw it once. Crazy looking. I scraped, Peelstop, (Zinnser) skimcoated, primed, painted. House built around the same time. Been 3 years and holding. Before it wouldnt last 3 months before it crazed.

PlainPainter · 07-27-2007, 06:41 AM

I do those jobs all the time - my sis' house was from early 50's with the gypsum lattes, the kind only 2 feet wide with drilled holes. With a brown coat/putty coat 2-coat plaster system. Had all paper over the walls - I used boiling hot vinegar and a tiger tool to take off paper. And then once paper was off - kept cleaning the walls down with really hot white distilled vinegar - until the walls were clean. This neutralizes everything - and then used an interior/exterior oil quick dry primer, like coverstain. Has been flawless! If you have a moisture problem - fix it! Nothing will stick with a continuing water ingress.

RockStar · 07-27-2007, 07:04 AM

Once walls are prepped and ready to go, take a setting type compound (I prefer Durabond 120 to allow time and because it dries harder than the sandable types.
You will need to purchase a roll of mesh that's used for EIF's (dryvit, etc..). It comes in three foot wide rolls.
Apply the Durabond and put the mesh right over the wet mud and wipe till you see mesh showing through and let dry. Not only will the mesh stop smaller areas from coming loose it will straighten any imperfection out at the same time.
Do two skim coats with a lightweight compound and your done.

Keep the mesh back about 1/2 inch from all trim etc and you wont have to replace it while still getting a strong perfectly finished wall.

If you have larger areas coming loose from the lath, take washer screws and screw through the compound and mesh while its still wet, smooth it out with your knife of trowel and it will pull it back in and hold it when it dries.

Try one wall and you will be amazed how fast it goes and how good it works.
The best way to repair old plaster........NO DOUBT!

If you need to find the materials try BuyMyMaterials.com and you should find what you need near you.

Good luck:

fatherson · 07-28-2007, 12:18 AM

Try using a calcimine coater it should bond. The two I can think right now of are,

Old Yankee - Home Depot (You Can Do It, We Can't Help) and

Gards by Zinsser, don't know what store in your area might carry it.

Other than that you'll need to skim coat the walls.

chris n · 07-28-2007, 04:23 AM

Gards by Zinsser, don't know what store in your area might carry it.

Draw tite will also work,if you can get it.

jackrabbit5 · 07-28-2007, 07:50 AM

Quote:

Originally Posted by chris n

Gards by Zinsser, don't know what store in your area might carry it.

Draw tite will also work,if you can get it.

I had a job several years ago where I had the opportunity to test DT over calicimine. While it probably worked better than your better latex primers, it still failed. What I've found to work best on calcimine is straight Emulsabond.