Thirty years ago, many apartment wall assemblies had Sound Transmission Class (STC) ratings of less than 45, which meant that the sounds of Led Zeppelin could easily pass through to an adjoining unit. But today’s IBC code requires all new construction—both multifamily and single-family—to use wall assemblies that deliver at least STC 50. Yet, even that level of protection allows loud sounds from a music system to still be faintly heard.

Fortunately, many wall assemblies now offer 60-plus STC ratings—and architects don’t have to pay extra for the improved sound reduction. It’s just one of many features that are now standard in innovative wall assemblies like the UL U350B interior load-bearing wall assembly featuring LP FlameBlock Fire-Rated oriented strand board (OSB) sheathing. This assembly provides an STC rating of 62, thanks in part to its resilient channel design.

Sound reduction isn’t the only noteworthy attribute of this assembly. It’s less expensive and easier to install than area separation walls using shaft liner. Moreover, it reduces load and costs associated with material and labor compared to options that require an extra layer of gypsum.

The fire-rated OSB used in these types of assemblies combines both flame-spread resistance and burn-through resistance in a single panel—and has design values for load/span and shear that are superior to many common alternatives at the same thickness. In addition, this type of fire-rated OSB carries an Exposure 1 classification, which means it can withstand exposure to moisture during normal construction delays.

Partition walls that use fire-rated OSB are helping architects achieve multiple objectives—sound reduction, lower labor/material costs, and the design freedom that comes from reduced load.

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