1. Floor Topping (optional, not shown): Gypsum concrete, lightweight or normal concrete topping.
2. Floor Sheathing: Minimum 23/32 inch thick tongue-and-groove wood sheathing (Exposure 1). Installed per code requirements with minimum 8d common nails.
3. Structural Members: Wood I-joists spaced a maximum of 24 inches on center.

	Minimum I-joist flange depth: 1-1/2 inches	Minimum I-joist flange area: 2.25 inches2
	Minimum I-joist web thickness: 3/8 inch	Minimum I-joist depth: 9-1/4 inches

See ASTM D 5055-07 for qualification requirements.

4. Gypsum Wallboard: Two layers of minimum 1/2 inch Type C gypsum wallboard attached with the long dimension perpendicular to the I-joists as follows:

4a. Wallboard Base Layer: Base layer of wallboard attached to bottom flange of I-joists using 1 inch Type S drywall screws at 12 inches on center. End joints of wallboard centered on bottom flange of the I-joist and staggered.

4b. Wallboard Face Layer: Face layer of wallboard attached to bottom flange of I-joists through base layer using 1-5/8 inch Type S drywall screws spaced 12 inches on center on intermediate joists and 8 inches on center at end joints. Edge joints of wallboard face layer offset 24 inches from those of base layer. End joints centered on bottom flange of I-joists and offset a minimum of 48 inches from those of base layer. Additionally, wallboard face layer attached to base layer with 1-1/2 inch Type G drywall screws spaced 8 inches on center with a 4" stagger, placed 6 inches from face layer end joints.

5. Finish System (not shown): Face layer joints covered with tape and coated with joint compound. Screw heads covered with joint compound.

	Fire Tests conducted at NGC Testing Services, Inc.	Report No: FC-687	January 25, 2007

STC and IIC Sound Ratings for Listed Assembly
Without Gypsum Concrete				With Gypsum Concrete
Cushioned Vinyl		Carpet & Pad		Cushioned Vinyl		Carpet & Pad
STC	IIC	STC	IIC	STC	IIC	STC	IIC
-	-	-	-	-	-	49 b	55 b

^a This assembly may also be used in a fire-rated roof/ceiling application, but only when constructed exactly as described.
^b STC and IIC values estimated by David L. Adams Associates, Inc