How to repair water-stained cement wall?
Question:I have an interior cement wall that is stained from old water leaks from the other side. (The leaks are now fixed.) The cement in this area is now somewhat powdery and stained. How can I repair or treat this so that when I paint over it, the stain doesn't bleed through? Also, the surface is now a bit rough for painting. Any suggestions??
Answers:
you can parge it
Scrape off as much of the white stuff with a wire brush.
Purchase Dry-Lock Etch which comes in a powder form and mix it in water per the container directions. Dump that into a stray bottle and spray the wall. Let it sit for a couple minutes, then carefully use an old paint brush or something that won't fling the Dry-lock etch back on you, to scrub it again. You'll then need to rinse this off with water before painting. That should remove the white powder from the wall.
You can use muratic acid instead of Dry-Lock Etch, but you need good ventilation.
I have gone over basement water stains with Killz but make sure you have good ventilation.
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