Q. We're converting an old building for use as apartments. We want to use a thin, polymer-modified, acid-stained concrete overlay on the concrete floors but we're concerned with noise transfer through the floor. To control this, we hope to use an acoustic underlayment such as cork or an Enkasonic mat. Will the thin overlay perform adequately over such a substrate?

A. We doubt it. Thin, cementitious overlays are relatively brittle materials that require a solid foundation. Loadings from foot traffic or apartment furnishings are likely to crack the overlay by causing the acoustic underlayment to deflect. Check with the overlay manufacturer to be sure, but we bet they'll advise against this application of their product.