What is IIC?

Impact Insulation Class (IIC) measures how well a floor-ceiling assembly blocks impact sounds like footsteps, dropped objects, and furniture movement. Unlike STC which measures airborne sound (voices, music), IIC specifically addresses structure-borne vibrations that travel through the building.

Higher IIC = better isolation. An IIC of 50 is code minimum for apartments; 55+ is recommended for quality living; 60+ is needed for recording studios or luxury condos where footfall noise must be virtually inaudible.

Floor-Ceiling Assemblies ?

Impact Insulation Class ?

Select an assembly

Total Deficiency ?

Max Single ?

Code Compliance

IBC 2021 (dwelling units) IIC 50

UBC / California Title 24 FIIC 45

Luxury residential IIC 55+

Recording studio IIC 60+

What Does This Mean?

Select an assembly to see expected footfall noise perception.

ISPL Curve Comparison

ASTM E989: IIC = 110 − (ISPL at 500 Hz contour intersection). Total deficiencies ≤32 dB, no single frequency exceeds 8 dB above contour. E989-21 | E492

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