(a) The maximum spans for joists and rafters shall be as shown in the following tables. All lumber shall be as identified in Section 1466.03.
SPAN TABLES FLOOR JOISTS
40 Lb. Live Load and 20 Lb. Dead Load
UNSUPPORTED LENGTH
40 Lb. Live Load and 20 Lb. Dead Load
UNSUPPORTED LENGTH
Nominal Size in Inches | Spacing in Inches | D. Fir Larch Const. Y Pine | Western Hemlock Const. | Eastern Spruce Western White Spruce Sitka Spruce White Fir Const. | Engelmann Const. |
2x6 | 12 16 | 10'6" 9'8" | 9'8" 8'9" | 9'0" 8'0" | 8'0" 7'0" |
FOR ADDITIONS AND STORAGE SHEDS ONLY.
2x8 | 12 16 | 14'0" 12'6" | 12'8" 11'10" | 12'0" 11'0" | 10'0" 8'6" |
2x10 | 12 16 | 17'0" 15'8" | 16'0" 14'10" | 15'4" 14'0" | 12'9" 11'1" |
2x12 | 12 16 | 20'0" 18'6" | 18'8" 17'0" | 18'0" 16'2" | 15'5" 13'5" |
SPAN TABLES ROOF RAFTERS
Horizontal Measurements
30 Lb. Live Load 10 Lb. Dead Load 40 Lb. Load
3-1/2/12 to 6/12 Roof Pitch (See note below)
Nominal Size in Inches | Spacing in Inches | D. Fir Larch Const. Y Pine | Western Hemlock Const. | Eastern Spruce Western White Spruce Sitka Spruce White Fir Const. | Engelmann Const. |
2x6 | 12 16 | 15'0" 13'2" | 14'0" 12'2" | 12'3" 10'7" | 8'9" 7'7" |
2x8 | 12 16 | 19'10" 17'1" | 18'6" 15'6" | 16'6" 14'1" | 13'6" 11'8" |
2x10 | 12 16 | 24'0" 22'0" | 22'10" 20'8" | 20'8" 17'11" | 17'8" 15'4" |
NOTE: For slope less than 3-1/2/12 use Floor Joist Span Tables for Roof Rafters.
For slope over 6/12 roof design must be submitted to the Building Officials.
DEFLECTION: For 20# psf live load span in inches divided by 240
STRENGTH: LL-20# psf plus 10% psf dead load
NFPA Table J-4 determines fiber stress value
CEILING JOISTS (Limited Attic Storage Where Development of future rooms is NOT possible) Moisture content not to exceed 19% | |||||
Size | O/C Spacing | D-Fir & Larch or S.Y.P. | Hem-Fir Hemlock and/or W-Fir | SPF= Spruce-Pine Fir | Engelmann Spruce |
1.7E-1450f | 1.4E-1150f | 1.3E-1000f | 1.2E-925f | ||
2x6 | 12 16 | 15-7 13-7 | 13-11 12-1 | 13-0 11-0 | 12-5 10-10 |
2x8 | 12 16 | 20-6 17-11 | 18-4 15-11 | 17-2 14-9 | 16-4 14-3 |
2x10 | 12 16 | 26-1 22-9 | 23-6 20-3 | 22-0 18-10 | 20-10 18-1 |
(b) No member shall be cut, notched or bored in a manner which would cause the permitted unit stresses to be exceeded.
(1) Holes may be bored in the middle third of the depth and length of a horizontal member when such holes are not larger than one-fourth of the depth of such horizontal member and when knots are not a factor.
(2) Joists framing into the side of a beam or girder shall be hung in metal stirrups or rest on a two-inch by two-inch ledger strip. The notch in joist and resting on ledge strip shall not exceed one-fourth the depth of such joist.
(3) The top or bottom edges of joists may be notched not to exceed one-sixth of the joist, provided such notching is not within the middle third of any joist span.
(4) Any joist or horizontal member that has been notched or bored in excess of the above shall be reinforced or adequately supported.
(c) Floor joists shall be doubled under all bearing partitions which run parallel to the floor joists. Doubled joists shall be separated and blocked at four-foot intervals when piping or duct work occurs.
(d) Wood trimmers, headers and tail joists over six feet long shall be hung in approved metal hangers unless supported on walls or girders, and shall be doubled. Headers and trimmers under four feet may be single if hung in approved hangers or on not less than two-inch by two-inch ledger board.
(e) All horizontal members shall have a bearing equal to the working stresses permitted by this Building and Housing Code, and all members resting on masonry walls shall have a bearing on not less than four inches.
(f) Joists bearing on wood stud partitions or stud walls shall bear on wood plates of the same width as the studding or on one-inch by six-inch ribbon strips set into the studding.
(g) Ends of lapped joists shall bear on girders or bearing partitions and shall be securely nailed to plate and to each other.
(h) The cutting of joists, beams, girders, columns or other structural members to impair their safety shall not be permitted. Where floor joists are cut to exceed three inches, the notched joist shall be trussed and the joists on each side of the one cut shall be doubled or reinforced. Where a stud is cut completely through, the studs on each side of the one cut shall be doubled. Where the top plate of a wall or partition is cut or notched to exceed two inches, a reinforcing strap of iron or steel at least one-fourth of an inch thick and one and one-half inches wide, and of sufficient length to extend at least six inches beyond each side of the cut or notch, shall be securely attached to the plate with bolts or two ten-penny nails at each end. Where the plate is cut completely through, a reinforcing strap shall be placed on both sides of the plate.
NOTE: All horizontal members shall be nailed, spiked or fastened in a manner such that the unit stresses of such members shall not be exceeded.
(Ord. 42-1981. Passed 2-23-81.)