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Blisters in painted aluminum siding

I have owned my 1920's bungalow for three years now. On the first floor, it has white aluminum siding which was getting very dull and dirty, so I wanted to get it pressure-washed. Before doing so, I closely inspected the siding and noticed that there were many small (1/16" diameter) blisters in the paint. There were even a couple of large (3/4" diameter) ones. You can push the blisters in with your thumbnail or break them open to reveal another coat of white paint. These blisters are only on the two walls that receive direct sunlight, and they are mainly on the bottom of each lap. There are thousands of these tiny blisters.
So, my problem is what to do with them. Pressure-washing will definitely remove them all, but it won't remove all the paint off the siding. I've had painting companies give me two different opinions. One is that I should just pressure wash to remove the loose stuff and then paint over it. The other opinion, though, is that all the paint needs to be removed prior to repainting. Otherwise, you'll be able to see all the edges where the blisters were removed through the new paint. It was the opinion of this last painting pro that it would be less expensive to remove all the siding and have the entire house resided. That seems like such a waste to me because the siding is in great condition; it's the finish that's bad. I'm stumped as to how to proceed. Perhaps there's a filler or very thick paint that would cover the blister holes after it's pressure washed? Any input would be greatly appreciated. Thank you in advance.

Re: Blisters in painted aluminum siding


I have never run across what you are describing. I would agree with the one pro who opins that stripping would not be cost effective. I would lean toward a very thorough power washing. Some sanding of rough areas with a medium grit paper might obscure the roughness. Normally, I would not prime aluminum siding, but simply go with a quality 100% acrylic housepaint, preferably of low sheen. However, in your case I might consider an acrylic primer to facilitate more "build" of the paint film to hide imperfections. You might make a sample in a small area of your siding. You have nothing to lose if your other option is to replace the siding.

Re: Blisters in painted aluminum siding

I would power wash the blisters off. Then prime with Kilz 2, 100% acylic latex primer,then paint with top color. The blistered area will show a little but for the cost of the replacing siding,I could live with it.

Re: Blisters in painted aluminum siding

Thanks for the replies. I think those ideas sound like my best bet at this point.

Re: Blisters in painted aluminum siding

I had a similar situation to your house - white aluminum siding with failing white paint. If possible, do the pressure washing yourself, or babysit whomever is doing it for you, because it really needs a careful washing. It is not sufficient for someone to stand on the ground and spray down the house, every inch of the siding must be shot with water from less than six inches away (too close can actually dent the siding, however).
But if your paint is also chalky like mine was, and the water runs off the house like skim milk, avoid what happened to me. I power washed the heck out of the siding, waited a few days for it to dry thoroughly, then painted the house with a brush. It looked great, and from a few feet away, I couldn't see the subtle surface differences where the old paint had chipped off. HOWEVER, a few days later it rained, and apparently some of the milky white water from when I pressure washed had settled around the trim and in cracks and crevices, and the rain washed out that remaining sediment, and it stained the new blue paint with white streaks. So, be sure to give the house a good rinse or three to avoid my pain.
Lastly, by washing the house myself, and paying some college kids to help me paint it, I did the whole house for under $500. So don't let anyone tell you that you need $10,000 worth of new siding.

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