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Sealing old plaster for texture and paint


m4j2t's Avatar
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03-06-13, 10:21 PM   #1  
Sealing old plaster for texture and paint

Hello,

I have a basement with plaster walls, over concrete foundation, and I'm trying to seal the plaster so I can texture and paint it. I tried a test wall, with latex primer directly on the plaster, then knock down texture, and finally another coat of primer. It was a disaster. The entire wall peeled off.

So I went out and bought a $100.00 5/gal can of Zinsser oil based sealer and reprimed. I tested the primer adhesion by putting a strip of duct tape on the wall, and the primer comes right of with the duct tape. Here's a link to a couple photos. I couldn't get any of them to upload...

The first is the latex primer, and texture peeling off.

http://dl.dropbox.com/u/40374015/Diy...%2011%2025.jpg

This is after sealing with the Zinsser oil based primer sealer and trying a pain sample. the yellowish color it actually the color of the plaster.

http://dl.dropbox.com/u/40374015/Diy...%2003%2055.jpg

If anyone has any ideas on how to seal and paint this wall properly, I'm all ears. It's very gritty, and although the Zinsser pirmer isnt peeling of at all, in fact it's very difficult to scrape off, I'm unnerved by the ease with which the duct tape removed the primer from the plaster.

 
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marksr's Avatar
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03-07-13, 04:28 AM   #2  
How long did you let the oil primer cure before removing it with the duct tape?

Were there any coatings applied to the plaster previously? The fact that the latex primer peeled points to some type of contaminant [or oil base enamel] on the plaster hindering latex's ability to adhere. Solvent based primers are almost always the answer if the contaminant can't be washed off.


retired painter/contractor avid DIYer

 
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03-07-13, 07:12 AM   #3  
I cured the oil based primer for at least seven days. Then I let the tape sit on the primer for a day before pulling it off.

I do not believe the plaster was previously coated. I removed original construction furring strips and wooden panels to reveal this wall. The wall is very chalky and gritty. A light powder rubs off on your finger when you run it across. Everything I read pointed to the oil based sealer. Now the whole room is covered with it. can I put a solvent primer over that. You've seem to indicate I can...

Thanks for your help!

 
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03-07-13, 09:26 AM   #4  
The chalkiness is the problem. When it can't be washed or brushed off - an oil base primer is needed. For service cases they make a thin masonry sealer that penetrates the chalk to bind it up. It's possible that Zinnser's Gardz would do the same thing. You might be ok with just using an oil base primer.

After a week the primer is definitely cured although duct tape is probably the stickiest thing you can apply to a painted surface and try to pull it off later without damage. For what it's worth - you should never use duct tape on a painted surface if you intend to remove the duct tape later..... that's why I think you'll be ok with oil primer.


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03-07-13, 04:10 PM   #5  
At some time in the past, something was used on the walls that is preventing good adhesion with you latex based products. Duct tape applied to any wall, newly painted or old work, will pull the paint off so your better test is scraping which you said adhesion was good. If you have applied texture to most of the room already with latex, you will have to scrape it clean and get the oil based primer down to the bare plaster and then texture from their.

I've only experienced your problem once. It was a hotel room, I had done dozens before without issue, but this one room baffled me. We prepped it the same all all others. Primed, sprayed orange peel texture, primed again and painted. After we were done, we noticed bubbles in a couple of places. I took a 6" putty knife and was able to start at one end of the room and scrape all the way to the other and all layers peeled right off. We scraped the whole room, primed with regular Kilz oil based (hate the smell) and proceeded from there. The room still in good shape 7 years later. To this day, I don't know what happened, but the oil based primer worked.

 
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03-08-13, 04:07 AM   #6  
For service cases they make a thin masonry sealer that penetrates the chalk to bind it up
Meant to say - For severe cases ......


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03-08-13, 07:02 AM   #7  
Thanks everyone for the replies. I did scrape the entire test wall where the latex was (150 sq ft). The largest piece I got down was 2' by 3'. I primed the the entire room with the oil primer (I did do a test with a sample can first), and then I did the duct tape test. I agree the duct tape test was ridiculously extreme. I've tried scraping the primer off with a very sharp scraper, but I have to dig into plaster to get anything beside a few very small specs off. Those specs come off where there's a small bump from the old brushed style texture finish, so I'm probably biting into plaster there too. I'm going to try to texture and prime a the test wall area again, and I'll post the results. I've go tsome repair work to do first, so it may be a couple weeks.

Thanks for everyone's help!

 
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03-08-13, 09:41 PM   #8  
Keep us updated when you can!

 
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03-16-13, 11:54 AM   #9  
So you are painting/texturing a below-grade concrete wall. Is there any insulation/buffer between the plaster/drywall and the wet concrete? Did you check the moisture content of the plaster before starting? Are you located near the center of your state where most of the precipitation happens? MorganMaps | U.S. precipitation map

Blocking/sealing the plaster may not be such a good idea if there are any moisture sensitive materials under it on the concrete wall; wood sleepers, etc. Any moisture coming through would be blocked at the plaster to rot the wood below; "If basement wall systems are designed and constructed to dry to the interior regardless of where insulation layers are located interior vapor barriers must be avoided. This precludes interior polyethylene vapor barriers installed over interior frame wall assemblies or any impermeable interior wall finish such as vinyl wall coverings or oil/alkyd/epoxy paint systems." From; BSD-103: Understanding Basements — Building Science Information

OR, do you have an perimeter interior drainage system with sump pump?

Gary

 
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