Acoustical Values Added to AWC’s DCA 3

Apr 02, 2020

LEESBURG, VA. – The American Wood Council (AWC) has released an updated version of Design for Code Acceptance (DCA) 3 – Fire-resistance Rated Wood-Frame Wall and Floor/Ceiling Assemblies, which now includes sound transmission characteristics of floor/ceiling assemblies. A free pdf version of DCA 3 can be found on the AWC website at

While DCA 3 primarily focuses on the fire-resistance ratings of tested wall and floor/ceiling assemblies, the document also provides useful information regarding detailing of intersections of fire-resistance rated assemblies and sound transmission characteristics of the floor/ceiling assemblies described in DCA 3.

Model building codes stipulate minimum required Sound Transmission Class (STC) and Impact Insulation Class (IIC) values for floor/ceiling assemblies. The latest revisions to DCA 3 include the addition of STC and IIC ratings for multiple variations of the fire-resistance rated floor/ceiling assemblies described within the document.

“The STC and IIC values given in DCA 3 provide an additional tool for designers to use in demonstrating compliance with code requirements and acoustical design objectives,” said Jason Smart, AWC’s Engineering Technology Manager.

These recently added STC and IIC ratings were estimated through engineering analysis based on the empirical model described in AWC Technical Report 15 (TR 15), Calculation of Sound Transmission Parameters for Wood-Framed Assemblies, which is also available for free on the AWC website: