Basement Paint coming off in giant flakes

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Old 02-18-12, 08:48 AM
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Basement Paint coming off in giant flakes

Ok Giant is an exaggeration but the paint is flaking/bubbling off the walls in decent sized chunks.
It's 50's era poured concrete. I don't have any signs of water accumulating but as hinted by the paint chipping off there is a bit of dampness in the air. (no sump pump or floor drain)

WHat should I do to prep and paint the basement so that the paint sticks?
I don't have any near term plans to "finish" my basement but would like to get it looking pseudo presentable as a man cave/gym type room and less like a dank crumbling storage area. I'm also thinking about rescuing a dog and want to setup the basement as a safe place to leave him until I can trust him with my hardwood floors in the rest of the house.

 
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Old 02-18-12, 10:55 AM
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It looks to me like, well, parts of my basement.
Seriously, though I'd say that you have moisture migrating through the concrete, causing not just the feeling of dampness that you mentioned, but the efflorescence (sp?)- the white mineral-salt like deposits, and the bubbling of the paint.
If you can address the moisture problems, and I'm sure the more knowledgeable /experienced folks will chime in later, you'll address the bubbling as well.
 
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Old 02-18-12, 02:35 PM
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I agree it's a moisture problem and they are best addressed on the exterior. That said, a good cleaning and a coat of drylok might be enough insure a decent paint job.
 
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Old 02-18-12, 07:38 PM
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Any good tips addressing moisture on the exterior?
 
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Old 02-18-12, 08:50 PM
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Looks to me like there's more going on than just paint not sticking. If it were simply a paint adherence problem, the visible concrete at each "flaked" area would be smooth and grey. Yours looks rough, with some colored, fractured aggregate visible near the center of each. If the areas are actually smooth, and just appear rough in the photo, I apologize for barking up the wrong tree.

But if the flaked areas are indeed rough to the touch, then report back such that I can tell you what I think the problem might be.
 
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Old 02-19-12, 05:33 AM
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Any good tips addressing moisture on the exterior?

Make sure all the downspouts are piped away from the foundation is the easiest thing to do. Grading the land away from the house is next. The rest involves excavation sealing the exterior of the foundation and drain tile.
 
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Old 02-19-12, 10:31 AM
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Yes the exposed concrete underneath is a bit rough. It looks like there is a bit of rust at the center of many of these spots.
 
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Old 02-19-12, 12:08 PM
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I suspect what you have is mild sulfation occurring within the concrete. It usually happens when certain minerals (either in the concrete itself or in the aggregate base or soil it rests on) undergo a chemical reaction, causing them to swell and expand slightly. In your case, it could well be iron pyrites, given the rust-colored aggregate you mentioned. It forms sulfuric acid and other compounds when in contact with certain minerals in the mix, with the net result being small divots breaking out at the surface when the thin mortar layer cannot resist the tensile forces being exerted on it.

The only reason I'm familiar with the process comes from my experiences as a DOT bridge engineer. About 20 years ago, we had 2 new twin structures in my district whose adjacent abutments began crumbling within a few years of having been built. At first, it was just surface divots like yours, but later the entire concrete matrix just disintegrated. Our testing lab took core samples, and had them analyzed by a specialized lab that came up with the sulfation explanation. We eventually completely replaced both abutments, using concrete made with Type V Portland cement, which has a high resistance to sulfate attack.

I don't expect your walls will require replacement in your lifetime, based on the degree of surface deterioration visible now. For example, our abutments were having football-sized chunks of concrete breaking off after just a few years of service. If you do some research on it, there might be some surface treatments available today that could mitigate what you've got, after all of the paint is removed first. If it were mine, I'd be tempted to give the walls a brush-off sand blasting treatment, for a uniform exposed aggregate look. With the right sealer, it could look quite nice. For a better diagnosis and possible remedy, a local testing lab (or even concrete repair specialist) should be able to help you.
 
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Old 02-19-12, 12:20 PM
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You really cant paint the walls with any success if you dont stop the exterior water migration
 
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Old 02-19-12, 02:27 PM
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I suspect what you have is mild sulfation occurring within the concrete.
I suspect this is correct.
you really cant paint the walls with any success if you dont stop the exterior water migration
I've done a lot to clear overgrowth out around the the house after moving in back in winter 2009 and made sure the ground is graded away from the house. I've also redirected the downspout away from the foundation. Maybe if I'm lucky for once I've already mitigated much of the water problem and I'm only seeing old damage.

The house was built in 1951 and it only looks as if there were 2 layers of paint on the walls over all that time so i think it has been a very slow process.

I guess my plan at this point will be to try to do some cleanup and repainting (?drylok?) and reassess when (or hopefully if) this starts happening again. Unless anyone has better recommendations?
 
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