Understanding IIC Claims for Soundproofing Underlayments

floor soundproofing

It’s a common occurrence: you see a 1-page data sheet claiming light-weight and inexpensive materials getting IIC ratings of 70 or higher. These data sheets are littered with incomplete information and undefined assemblies.

When you request the test data, it’s either difficult to attain, or when received, completely irrelevant.

So, where do you go from here?

Request Exact Attenuation Tests

The number one thing Acoustical Consultants recommend today is requesting exact attenuation tests from a third party lab. This removes the conflict of interest inherent between a technical and marketing team. When reviewing tests, find applicable configurations that are as close to your floor design, and make extrapolations from there if needed.

For instance, you may see an underlayment that shows an IIC of 55 on 6” light-weight concrete and acoustical ceiling (resiliently mounted 5/8” gypsum board), and with ¾” OSB and ¾” Gypcrete above. If your assembly design is similar, but with 1-1/2” Gypcrete, then you may add 1-2 points. The PCI (Prestressed Concrete Institute) has extensive data on incremental changes in building materials. On the other hand, if your reference design has no resiliently mounted ceiling, then you will need to remove 8-10 IIC points (as a rule of thumb). Better yet, request the same test from your supplier without an acoustic ceiling – top soundproofing vendors have numerous tests in dozens of configurations.

For further reference, see the list of 3rd party tests performed on the Floor Blokker membrane here. Acoustical technicians are available to answer any questions that you may have.

Acoustics Expert

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