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Joist span Based on No.2 or better wood grades. Design Load =40#LL+ 10#DL,Deflection= L/360 SouthernHem Fir pine Western cedar 12"OC 16"OC 24"OC 12"OC 16"OC 24"OC 12"OC 16"OC 24"OC 2x6 10-0 9-1 7-11 10-3 9-4 7-7 9-2 8-4 7-3 2x8 1 3-2 12-0 10-6 13-6 11-10 9-8 12-1 11-0 9-7 ----------- -------- 2x10 16-10 15-3 13-4 16-2 14-0 11-5 15-5 14-0 12-3 2x12 20-6 18-7 16-3 19-1 16-6 13-6 18-9 17-0 14-11 Sample calculations for using joist span, beam size and footing size tables Case I solution: Refer to tables for joist,beam and footing size requirements. a Example:a = 12 feet;Post spacing =8 feet Use the joist span table to find the acceptable joist sizes for a 12 foot span, 2x8s at 12 inches O.C.,2x1 Os at 16 inches O.C.or 2x12s at 24 inches O.C. Use the Beam and footing sizes table and find the 8 foot post spacing column. With a 12 foot deck span, the beam may be either two 2x8s or two 2xl0s, depending on wood used. Depending on the type of soil, the footing diameter at the base must be a minimum of 12 inches, 10 inches or 9 inches for the corner post and 17 inches, 14 inches or 12 inches for all intermediate posts. Case II solution: Use "a"to determine joist size and "a"+ "2b"to determine beam and footing sizes. The length of"b"is restricted by both the length of"a"and the size of the joists. Example:a =8 feet,b= 2 feet, Post spacing = 10 feet a b Refer to the joist span table.For an 8 foot joist span,either 2x8s at 24 inches O.C. or ~� 2x6s at 16 inches O.0 are acceptable. For sizing the beam, use a joist length of 12 feet (8 feet + 4 feet) and a post spacing of 10 feet.The beam and footing sizes table indicates that the beam may be either two 2x10s or two 2xl2s, depending on wood used. Depending on the type of soil, the footing diameter at the base must be a minimum of 15 inches, 12 inches or 11 inches for the corner post and 20 inches, 17 inches or 15 inches for all intermediate posts. Note that because of the 2 foot cantilever all footing sizes were increased by 1 inches as required by footnote 2 at the end of the table. Case III solution: Use "a"or "b"whichever is greater, to determine joist size. Use "a"+ "b"to determine the size of Beam 1 and the post footing size for the posts supporting Beam 1.Use joist length "b"to determine both the size of Beam 2 and the post footing size for the posts supporting Beam 2. a►� b Example:a = 6 feet,b=7 feet, Post spacing =9 feet Joist size is determined by using the longest span joist (7 feet). The joist span Beam 1 Beam 2 table indicates that 2x6s at 24"O.C.would be adequate for this span. For Beam 1 and footings, use a joist length of 13 feet (6 feet + 7 feet) and a post spacing of 9 feet. The beam and footing sizes table indicates that the beam may be two 2x10s or two 2xl2s, depending on the wood used. Depending on the type of soil, the footing diameters for Beam 1 posts shall be 13 inches, 11 inches or 9 inches for the corner (outside) post and 19 inches, 15 inches or 13 inches for all intermediate posts. For Beam 2 and footings use a joist length of 7 feet and post spacing of 9 feet. The beam may be two 2x8s or two 2x10s, depending on wood used. Depending on the type of soil, the footing diameters for Beam 2 shall be 10 inches, 8 inches or 7 inches for the corner posts, and 14 inches, 11 inches or 10 inches for all intermediate posts.