Blistering Paint

GWHRsuperhero

Im painting an interior concrete wall (cinder blocks) that had previous water damage. The painter before me tried to fix some minor damage with normal joint compound spackle and there was also few areas were the paint was bubbling up and peeling off. This was all just done couple months ago. I scraped and sanded out the spackle put in some concrete patch and scraped the bubbled paint. Next day I sanded down the whole area and spot primed the few areas that were bare concrete (with kilz latex primer). Then I applied a top coat of normal latex semi gloss paint. While the paint was drying it started to bubble in some areas. I scraped that and noticed it was taking off the two layers my paint as well as the old paint. Could this be due to the previous painter not using primer? Do i have to take off all the paint and prime the bare concrete? Or maybe if I switch to an oil paint since it doesn't have any water?

Danahy

You may need to solve the water / moisture / temperature problem with the cinder's as your first step.

What paint you use is irrelevant at this point.

ProWallGuy

I agree with the above. Not to mention that kilz latex is a really crappy primer for any substrate, let alone an unstable masonry one.

__________________
Wallpaper Hanger St. Louis
Digital Murals Installation

GWHRsuperhero

My boss claims the leak was fixed.. we did the roof awhile ago. There doesn't appear to be any moisture although the concrete is very cold to the touch. The areas that were just bare concrete wit the kilz and and topcoat look fine. The homeowner is holding out the check for the roof tell we get this done and my boss is wanting me to just make this look good so we can get our check. But it starts bubbling right away when it drys.

PlainPainter

The reason the paint blisters is that any curing paint that is stressed by heat and/or sunlight wants to expand - that is what makes latex great. Problem is that the previous layers aren't grabbing well onto the substrate then the paint blisters off ripping with it the old layers of paint. Your paint job is only as good as old paint that is going over. That being said - you can elect to keep scraping the bubbles and spot priming them and paint. Or totally strip with caustic paint strippers. And then once that is done, apply Muriatic acid to both etch the concrete and neutralize the previous caustics - and then rinse off with no pressure - otherwise you will get more effloresence. Then you can use a concrete stain - some specialty acrylic masonry sealer then paint - or do what I do - slap on acrylic latex enamel porch & floor paint to the concrete. Works great!

Brushslingers

It's called Ph, your blocks are leaking acid. Pick up a cheapo tester from your local paint store and explain to the HO that it will take a few weeks for the blocks to fully dry since they were not block coated to start with.

__________________
Benn

PlainPainter

If I was you - to make a quick job - after scraping - try sealing whole wall with Zinsser Guardz and hope to god it will seep through the pores of the previous layers of paint. IF you can lay that stuff down and it doesn't blister - then topcoat away - if this is inside with no sunlight - then I guess the water in your paint is enough to re-emulsify the previous layers with moisture thus causing it to lose its bond to the crumbling/chalky foundation. The guardz can reconnect to this chalk and stabilize the surface - and then paint. But your basic problem is a chalky damaged foundation wall that really needs to be stripped and addressed to before applying new paint. Certainly not a good enough reason for a homeowner to withold a check from you for doing a roof.

And this certainly demonstrates the need to be knowledgeable in these fields of contracting. Because you have done nothing wrong - and the customer has no clue and thinks it is your fault. Had you known what is going on - you could have informed your customer prior - and let them know what you will do - but couldn't guarantee results - and in either event a check is still due!

GWHRsuperhero

Ive only been painting a year now but I once painted a concrete wall with latex primer and latex topcoat with no problem. Whaddya mean by etch the concrete?

GWHRsuperhero

So basically, the guys that first painted should have first applied some kinda sealer. Or if they did use a sealer, could the water have gone through that and weakened it. So what needs to be done is strip it let it breath then reapply sealer. So should i blame this on the water or the previous painters?

Brushslingers

The water. Basic principle of concrete... can stay "green" for 40 years due to moisture seeping up, and is why we all seal crete with certain sealers rather than off the shelf primers... and is why tilemen use membrane or the roll on style sealers themselves. Concrete can hold water forever in the right circumstances... look at Greece. "Bubbling" on crete tells me the old lime blocks are wet, and killing the latex.

__________________
Benn