OSHA’s requirements for scaffold planks are primarily outlined in 29 CFR 1926 Subpart L. Here are the key requirements:
📋 General Requirements
Full Planking: Scaffold platforms must be fully planked or decked between the front uprights and the guardrail supports.-29
Platform Width: Platforms must be at least 18 inches wide when possible. If 18 inches is not feasible, additional fall protection measures (such as guardrails or personal fall arrest systems) must be used.-29
Load Capacity: Scaffold platforms must support their own weight plus at least four times the maximum intended load without failure. This is known as the 4:1 safety factor.-29
🌲 Material Specifications
Wood Planks (Lumber Quality):
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Must be “Scaffold Grade” lumber (construction-grade lumber is one-third weaker and is NEVER permitted)-40
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Must be graded by a recognized lumber grading association or independent grading agency-40
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The following quality indicators determine scaffold-grade lumber:-40
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Rings per inch (indicates density and strength)
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Slope of the grain (reflects structural integrity)
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Defects: Checks, notches, and knots that compromise performance
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Minimum Dimensions: For wood planks, the nominal thickness is typically 1½ inches (actual thickness may vary).
📏 Maximum Span & Load Capacity
For wood planks, the maximum permissible span depends on the intended load:
| Plank Dimensions | Maximum Intended Load (Uniform) | Maximum Span |
|---|---|---|
| 1¼” × 9″ or wider (full thickness) | 50 lb/ft² | 4 feet |
| 2″ × 10″ or wider | 75 lb/ft² | 8 feet |
| 2″ × 10″ or wider | 100 lb/ft² | 6 feet |
Note: These are non-mandatory guidelines from OSHA Appendix A to Subpart L. Employers must still ensure their specific scaffold system meets the capacity requirements.-7
For fabricated planks (non-sawn lumber, such as laminated or metal planks), the maximum span is determined by manufacturer recommendations based on three base ratings: light, medium, and heavy duty.-40
🔄 Overlap & Support Requirements
Abutted Planks: When scaffold planks are placed end-to-end to create a long platform, each abutted end must rest on a separate support surface. This does not preclude the use of common support members such as “T” sections, but each plank must have its own support point.-25
Overlapped Planks: When planks are overlapped to create a long platform:-26
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The overlap must occur only over supports
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Overlap must be no less than 12 inches (30 cm) UNLESS the platforms are nailed together or otherwise restrained to prevent movement
Plank Overhang:
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For 10-foot or shorter planks: Must extend 6 to 12 inches over the support center line-17
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For planks longer than 10 feet: Must extend no more than 18 inches over the end support-17
📉 Deflection Limits
If a plank deflects (bends) more than 1/60 of its span when loaded, it has been damaged and must NOT be used.–-17
For example:
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A 10-foot wooden plank: Maximum allowable deflection = 10 ft × (1/60) = 2 inches–
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A 5-foot wooden plank: Maximum allowable deflection = 5 ft × (1/60) = 1 inch
🔍 Gap Requirements
The space between adjacent planks, and between the platform and uprights, must be no more than 1 inch (2.5 cm) wide, unless the employer can demonstrate that a wider space is necessary for the specific work being performed.-34
🛠️ Inspection & Defects
Inspection Frequency: A competent person must inspect all scaffolds before each work shift and after any event that could affect structural integrity (such as high winds, impact, or modifications).-17-29
Wood Plank Defects to Check For:-17-40
| Defect | Description | Action |
|---|---|---|
| Splits | Cracks that go all the way through the board | Immediately discard the plank |
| Checks | Surface cracks that do NOT go all the way through | Monitor closely; if > ¼ inch, generally considered unsafe |
| Notches | Checks on the ends of planks | Monitor closely; heightened risk of expanding into splits |
| Knots | Large loose knots | Monitor; may compromise strength |
| Warping | Bends > ¼ inch | May indicate damage; inspect carefully |
| Laminate separation | Layers separating | Discard immediately |
| Concealing substances | Paint, plaster, mortar accumulated | Not permissible (makes inspection impossible) |
Re-use Restrictions: Wood planks used on mudsill projects (ground contact) are not permitted for re-use due to moisture absorption that can compromise plank quality.-40
⚠️ Additional Requirements
Alterations: Planks that have been altered (drill holes, saw cuts) are generally NOT acceptable unless specifically designed for that purpose.–
Fabricated Planks: Must be used in accordance with manufacturer specifications and load ratings. -40
Tagging: While not explicitly required for planks themselves, a competent person must verify that the scaffold and its components remain within safe load-bearing capacity. –
📋 Summary Table: Key Requirements
| Requirement | Specification |
|---|---|
| Material Grade | Scaffold Grade ONLY (never construction-grade) |
| Full Planking | Required between uprights and guardrail supports |
| Minimum Width | 18 inches (with exceptions) |
| Safety Factor | 4:1 (support 4× intended load) |
| Overlap (butted) | Each plank end on separate support |
| Overlap (overlapped) | Minimum 12 inches over support |
| Overhang (≤10 ft planks) | 6–12 inches over support centerline |
| Overhang (>10 ft planks) | No more than 18 inches |
| Maximum Deflection | 1/60 of span |
| Maximum Gap | 1 inch between planks/uprights |
| Inspection | Daily by competent person |
| Splits | Immediate discard |
| Checks | >¼ inch generally unsafe |
Remember: Scaffold safety is one of OSHA’s most frequently cited violations. Compliance isn’t just about avoiding citations—it’s about ensuring worker safety.
