Construction Joist Span Charts
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Wooden Decks
Floor Joist Span Tables
Maximum Joist Spans and Overhangs
Notes:
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Assumes 40 psf live load, 10 psf dead load, No. 2 grade, and wet service conditions.
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Assumes L/360 deflection.
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Maximum allowable overhang cannot exceed L/4 or ¼ of the actual main span. Assumes cantilever length/180 deflection with 220 lb point load. See photo (1) and (2) below.
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Incising assumed for Douglas Fir-Larch, Hem-Fir, and Spruce-Pine-Fir.
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Design values based on northern species with no incising assumed.
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Ledger shall be a minimum of 2x8 nominal. Joists and rim joists to which guard posts are attached shall be a minimum of 2x8 nominal.
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Joist length prescriptively limited to 18'-0" for footing design.
(1) Joist Attached at House and Bearing Over Beam
Photo from American Wood Council
(2) Non-Ledger Deck
Photo from American Wood Council
Dimension Lumber Deck Beam Spans (LB) Supporting a Single Span of Joists with or without Overhangs
Joist Spans (L) Less Than or Equal to:
Notes:
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Assumes 40 psf live load, 10 psf dead load, L/360 simple span beam deflection limit, cantilever length/180 deflection limit, and wet service conditions.
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Incising is assumed for Douglas Fir-Larch, Hem-Fir, and Spruce-Pine-Fir.
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Design values are based on northern species with no incising assumed.
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Beam depth must be equal to or greater than joist depth if joist hangers are used. See photo (3) option 3 below.
(3) Joist to Beam Detail
Photo from American Wood Council
Glued Laminated Timber Beam Spans (LB) Supporting a Single Span of Joists with or without Overhangs
Joist Spans (L) Less Than or Equal to:
Notes:
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Assumes 40 psf live load, 10 psf dead load, L/360 simple span beam deflection limit, cantilever length/180 deflection limit. Glued laminated timber shall be of naturally durable species or treated with an oil-borne or water-borne preservative in accordance with AWPA U1.
Spans for glued laminated timber beams not treated with oil-borne preservatives shall be multiplied by 0.89. -
Preservative-treated structural composite lumber of equal or greater capacity can be substituted.
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Beam widths of 3-1/8" or wider can be used for the tabulated 3-1/2" width, and beam widths of 5-1/8" or wider can be used for the tabulated 5-1/4" width.
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Beam depth must be equal to or greater than joist depth if joist hangers are used. See above photo (3) option 3.
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Beam span is prescriptively limited to 18'-0" for footing design.
These charts apply to single level residential wood decks only. Multiple level decks will likely have stairs that create additional concentrated loads not considered. JCS does not grade or test lumber, and accordingly, does not assign design values. The design values contained herein are based on the American Wood Council.
Accordingly, JCS does not warrant that the design values on which the span tables contained herein are based are correct, and specifically disclaims any liability for injury or damage resulting from the use of such span tables.
The conditions under which lumber is used in construction may vary widely, as does the quality of workmanship. Neither JCS, nor its members, have knowledge of the quality of materials, workmanship or construction methods used on any construction project and, accordingly, do not warrant the technical data, design, or performance of the lumber in completed structures.
Floor Joists
Click on the table # to view the downloadable span charts.
Wet-Service Floor Joists
The spans provided in these tables were determined on the same basis as those given in the code-recognized Span Tables for Joists and Rafters and Wood Structural Design Data, both published by AWC. Maximum spans were computed using Allowable Stress Design (ASD) and standard engineering design formulas for simple span beams with uniformly distributed gravity loads.
The calculated spans assume fully supported members, properly sheathed and nailed on the top edge of the joist or rafter. They do not, however, include composite action of adhesive and sheathing. Listed spans also do not include checks for concentrated or partition loads that may be required by building codes for specific occupancy or use categories. Uplift loads caused by wind also have not been considered.