What is the minimum sound transmission class required for walls, partitions, and floor/ceiling assemblies separating dwelling units?

The minimum sound transmission class (STC) required for walls, partitions, and floor/ceiling assemblies separating dwelling units is established to ensure adequate sound insulation and provide a level of comfort for occupants. An STC rating of 50 is considered the baseline for effective sound control in residential settings, as it is sufficient to reduce the transmission of normal conversation levels and other common household noises, thereby enhancing privacy and livability.

Higher STC ratings, while providing better sound insulation, can be unnecessary for typical dwelling unit separations and may result in increased construction costs or complexity without a significant benefit for the intended purpose. This standard reflects a balance between performance, cost, and practical implementation in building design, particularly in multifamily housing situations where noise separation is a key consideration.