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Q.In the search for a bounce-free floor, does either solid blocking or cross-bridging do anything to reduce the vibration caused by foot traffic? I haven’t been able to sense a difference between blocked or bridged floors and those without blocking or bridging. Consequently, I haven’t used either technique on my floor systems for several years.

A.Frank Woeste, P.E., and Dan Dolan, P.E., of Virginia Tech in Blacksburg, respond: We actually evaluated the effect of bridging or blocking on the vibrational performance of solid-sawn joists and I-joists in the laboratory. Full-scale floors were tested with and without bridging or blocking installed. Based on key indicators of floor performance, bridging and blocking had only a minimal effect on reducing annoying vibration. A much better way to control floor vibration is to increase the depth of the joist and limit the joist span, as described in our article, "Beyond Code: Preventing Floor Vibration" (Practical Engineering, 11/98).