Joint Compound Over Block
Q: "Should I trowel joint compound on my basement wall?"
We're planning to convert part of our basement into a recreation area. Can we trowel drywall joint compound over the concrete-block walls to smooth out the surface, then just paint it? It sure would save time and money.
—Rita Roberts, Vallonia, IN
Tom Silva replies: Standard joint compound sticks to lots of surfaces, but you'd be taking a big risk by spreading it on block walls, especially when they're below grade. I've heard of situations where all-purpose compound has been used this way, but the companies that make compound haven't certified it for this use.
I'd recommend that you coat your walls with portland cement stucco. It's a better bet than joint compound, because it forms a harder, more moisture-resistant surface, and it's fairly inexpensive, though it helps to have good skills with a trowel. Even if you don't, this is a perfect opportunity to save money and get the hang of mixing and troweling the stuff yourself. In a basement, who's going to notice if the results aren't perfect?