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Paula A. Brook
concrete prep. for repainting

I have a 100 year old home with concrete porch ledges around it (and also concrete window ledges). The concrete has been painted several times, and is peeling in places. I want to repaint this concrete, but need to prep it properly. I have used a hard wire brush and have tried sanding. Both do not work well.

Any ideas how to get the concrete ready for painting?
Thanks, Paula

Re: concrete prep. for repainting


Short of chemically stripping these areas, your best recourse is to just spot prime, re-coat and live with the blemishes. Oil paints are not the first choice on masonry, or on any exterior siding material. this is because they are almost impermeable to water vapor. This is what causes it to eventually fail. Cement, brick and many stones are very permeable and pass moisture toward the exterior. Acrylic/latex paints shun flowing rain water, yet allow vapor to pass on through without breaking its bond.

You can check for oil or latex by rubbing the surface with denatured alcohol or with Goof Off. Either will immediately attack latex, but not touch an oil. Also, oil usually dusts up when sanded, latex just gums up the sandpaper. Earlier coatings were probably oil. Upper layers could well be latex. If peeling is only to an earlier coat of paint, you probably have just an adhesion problem, rather than a moisture type peeling to bare stone..

If you decide to go the chemical route, the old fashioned, nasty ones are the best. Get a "paste" version that will not run off verticle surfaces. Also, the water rinsable ones are easier to wash away.

If they come clean enough, you might just seal them with a masonry sealer. If not, an acrylic based primer and house paint will give a good durable coating.

Re: concrete prep. for repainting

I am not a painter but I have removed paint coatings from Stucco which is a cement product.
To remove the paint you can use Back to Nature tough to strip, clean with water.
My choice for a coating would be a Mineral Paint. Look at KIEM silicate mineral coatings and masonry protection products.

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