Allowable spans for spruce, pine and fir.
by The U.S. Span Book for Major Lumber Species
MAXIMUM ALLOWABLE SPAN (ft.-in.)

Spacing (in.)	2 x 6				2 x 8				2 x 10				2 x 12
Grades	Sel Str.	No.1 No.2	No.3		Sel Str.	No.1 No.2	No.3		Sel Str.	No.1 No.2	No.3		Sel Str.	No.1 No.2	No.3
12	10-6	10-3	8-8		13-10	13-6	11-0		17-8	17-3	13-5		21-6	20-7	15-7
16	9-6	9-4	7-6		12-7	12-3	9-6		16-0	15-5	11-8		19-6	17-10	13-6
19.2	9-0	8-9	6-10		11-10	11-6	8-8		15-1	14-1	10-7		18-4	16-3	12-4
24	8-4	8-1	6-2		11-0	10-3	7-9		14-0	12-7	9-6		17-0	14-7	11-0

Allowable spans for APA performance rated I-Joists
by APA the Engineered Wood Association
SIMPLE SPANS ON CENTER SPACING (ft.-in.)

Depth	Joist Designation		12"		16"		19.2"		24"
9 1/2"	PRI-20		16-7		15-2		14-4		12-9
	PRI-30		17-1		15-8		14-10		13-11
	PRI-40		18-0		16-6		15-7		14-1
	PRI-50		17-10		16-4		15-5		14-5
	PRI-60		19-0		17-4		16-4		15-4
11 7/8"	PRI-20		19-11		18-2		16-6		14-9
	PRI-30		20-6		18-9		17-9		16-7
	PRI-40		21-6		19-7		18-2		16-3
	PRI-50		21-4		19-6		18-5		17-3
	PRI-60		22-8		20-8		19-6		18-3
	PRI-80		24-11		22-8		21-4		19-11
14"	PRI-40		24-4		22-1		20-2		18-0
	PRI-50		24-4		22-3		21-0		19-8
	PRI-60		25-9		23-6		22-2		20-9
	PRI-70		26-1		23-10		22-6		21-0
	PRI-80		28-3		25-9		24-3		22-8
16"	PRI-40		27-0		24-0		21-11		19-7
	PRI-50		27-0		24-8		23-4		20-2
	PRI-60		28-7		26-1		24-7		23-0
	PRI-70		29-0		26-5		24-11		23-1
	PRI-80		31-4		28-6		26-11		25-1

For more information on Performance Rated I-Joists visit: APA website