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Solid sawn wood planks, graded and stamped — the only planks Appendix A gives spans for.
Full thickness means the plank as sawn, before planing; nominal means dressed lumber, which is thinner than its name. The thicker plank of the same width spans further because stiffness rises with the cube of the thickness. Fabricated planks, metal decks and laminated veneer planks carry their manufacturer's rating instead.
The uniform load the scaffold is built to carry.
OSHA's light, medium and heavy duty are 25, 50 and 75 pounds per square foot (1.2, 2.4 and 3.6 kN/m²) spread over the whole span area. Choose the duty the scaffold is built and tagged for, not the one the job happens to need today.
Centre to centre of the bearers the plank spans between.
The clear span the plank bridges from one support to the next — usually the bay length, or the spacing of intermediate bearers where they are fitted to shorten it.
The width to be fully planked, from the front uprights to the guardrail supports.
OSHA requires each platform to be fully planked or decked between the front uprights and the guardrail supports, with no gap wider than 1 inch (2.5 cm) between units or at the uprights.
The actual width of the plank, not its name.
A dressed 2 × 10 is 9¼ inches (235 mm) wide and a rough-sawn one is wider. Measure one if you are not sure; the count across the platform depends on it.
Span used, as a share of the table's maximum
87.5 %
The distance between supports is 87.5% of the longest span Appendix A to OSHA's Subpart L gives this plank at medium duty. Appendix A is non-mandatory guidance, and a span within it is not a finding about the platform: the planks must be graded and stamped, in sound condition, and the platform may not deflect more than 1/60 of its span under load.
- Longest span Appendix A gives this plank at this duty
- 8 ft
- Your distance between supports
- 7 ft
- Left under the table's span
- 1 ft
- Planks across the platform, no gap over 1 in (2.5 cm)
- 5 planks
- Shortest plank, 6 in (15 cm) past the centre of each support
- 8 ft
- Most a platform may deflect under load, 1/60 of the span
- 1.4 in
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Scaffold Plank Span Calculator (OSHA Appendix A): 87.5 % — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
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How this was calculated
Formula source(s)
- Appendix A to Subpart L of 29 CFR Part 1926 (non-mandatory): maximum permissible span for 2 × 10 inch (nominal) or 2 × 9 inch (rough) solid sawn wood planks — full thickness undressed lumber 10, 8 and 6 feet at 25, 50 and 75 lb/ft²; nominal thickness lumber 8 and 6 feet at 25 and 50 lb/ft², none listed at 75; and 4 feet for 1¼ × 9 inch or wider full-thickness planks at 50 lb/ft²
- Appendix A to Subpart L: solid sawn wood used as scaffold planks shall be selected following the grading rules of a recognized lumber grading association or independent inspection agency, and identified by its grade stamp; allowable spans otherwise follow the National Design Specification for Wood Construction
- 29 CFR 1926.451(b): gaps between platform units no more than 1 inch (2.5 cm), (b)(1); each end at least 6 inches (15 cm) over the centerline of its support unless cleated or restrained, (b)(4); no more than 12 inches (30 cm) past its support for platforms 10 feet or less long and 18 inches (46 cm) for longer ones, unless designed or guarded for the cantilever, (b)(5); overlaps only over supports and at least 12 inches (30 cm) unless fastened, (b)(7); and (f)(16), platforms shall not deflect more than 1/60 of the span when loaded
Inputs used
- Plank
- 2 × 10 in (or 2 × 9 in rough), full thickness, undressed
- Duty
- Medium duty — 50 psf (2.4 kN/m²)
- Duty
- Medium duty — 50 psf (2.4 kN/m²)
- Distance Between Supports
- 7 ft
- Platform Width Between Uprights
- 4 ft
- Width of One Plank
- 9.25 in
Intermediate steps
- Longest span Appendix A gives this plank at this duty
- 8 ft
- Your distance between supports
- 7 ft
- Left under the table's span
- 1 ft
- Planks across the platform, no gap over 1 in (2.5 cm)
- 5 planks
- Shortest plank, 6 in (15 cm) past the centre of each support
- 8 ft
- Most a platform may deflect under load, 1/60 of the span
- 1.4 in
Confidence note: The distance between supports is 87.5% of the longest span Appendix A to OSHA's Subpart L gives this plank at medium duty. Appendix A is non-mandatory guidance, and a span within it is not a finding about the platform: the planks must be graded and stamped, in sound condition, and the platform may not deflect more than 1/60 of its span under load.
What this calculation does not cover
- Appendix A is non-mandatory. It offers these spans as one way of meeting the rule that each platform supports its own weight and at least four times its intended load; a plank rated by its manufacturer, or spans worked to the National Design Specification for Wood Construction, may differ.
- The spans are for solid sawn wood planks graded and stamped by a recognised lumber grading association or agency. An ungraded plank has no span here.
- Fabricated planks, metal decks and laminated veneer planks carry their manufacturer's span and load rating, not this table's.
- In the UK, timber scaffold boards are made to BS 2482 and their support spacing comes from the scaffold's TG20 guidance or design. Published figures for the thicker boards disagree, so this page gives none.
- The plank count assumes no gap wider than the rule's limit anywhere across the platform, including at the uprights; where planks must clear an upright the rule allows a wider gap there.
Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.
Sources checked 2026-09-21 · v1.0.0
Regulatory standards & verification citations3
- Appendix A to Subpart L of 29 CFR Part 1926 (non-mandatory): maximum permissible span for 2 × 10 inch (nominal) or 2 × 9 inch (rough) solid sawn wood planks — full thickness undressed lumber 10, 8 and 6 feet at 25, 50 and 75 lb/ft²; nominal thickness lumber 8 and 6 feet at 25 and 50 lb/ft², none listed at 75; and 4 feet for 1¼ × 9 inch or wider full-thickness planks at 50 lb/ft²
- Appendix A to Subpart L: solid sawn wood used as scaffold planks shall be selected following the grading rules of a recognized lumber grading association or independent inspection agency, and identified by its grade stamp; allowable spans otherwise follow the National Design Specification for Wood Construction
- 29 CFR 1926.451(b): gaps between platform units no more than 1 inch (2.5 cm), (b)(1); each end at least 6 inches (15 cm) over the centerline of its support unless cleated or restrained, (b)(4); no more than 12 inches (30 cm) past its support for platforms 10 feet or less long and 18 inches (46 cm) for longer ones, unless designed or guarded for the cantilever, (b)(5); overlaps only over supports and at least 12 inches (30 cm) unless fastened, (b)(7); and (f)(16), platforms shall not deflect more than 1/60 of the span when loaded
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