The load capacity of wood scaffold plank depends upon various circumstances. The plank type, size and thickness, and the intended span of the boards all influence how much dead load a specific scaffold board will support.
Strangely, there is no such thing as an “OSHA approved” scaffold plank. The Occupational Safety and Health Administration only “recognizes” certain solid sawn lumber grades and certain brands of manufactured wood planks as meeting their standards. OSHA does not endorse any specific product for the own liability reasons.
LVL scaffold plank is an engineered wood product manufactured in specific way such that the inherent defects ( knots, splits, etc.) found in lumber, are eliminated, thereby making LVL planks stronger and more homogenous. With LVL planks, every plank has identical strength properties so the performance is predictable and scaffold design can be planned most effectively.
Engineered wood scaffold planks (such as LVL) must be mechanically tested in order to verify that each plank has adequate strength and is in compliance with OSHA standards. The planks are literally passed through machines that verify the structural integrity and ensure the board has sufficient load carrying capacity. The plank manufacturer must to be able to substantiate or prove to their third party inspection agency that all new planks produced are compliant.
Extreme Fiber Bending (Fb) is the most crucial design value and it accounts for about 65% of the planks’ overall performance. It is a measurement of the correlation of a plank’s load carrying capacity in relationship to how much the board flexes before beginning to fracture and break. The Modulus of Elasticity (MOE) is the second most important design value and is a measurement of a planks’ stiffness or rigidity. It constitutes about 30% of the planks overall performance. Given the strength differences of each and every type of plank product, it is critical you refer to the product literature provided by the mill or manufacturer for the specific plank product you are considering.
OSHA standards specify that a wood plank should extend a minimum of 6” and maximum of 12” beyond the supporting points of scaffold frame.
Solid sawn wood plank is visually graded as a whole piece, therefore it is not recommended that a plank be arbitrarily cut into smaller sections. At a shorter length, there is a possibility that defects such as knots or splits might end up being located exactly where the plank needs to bear on the scaffold frame. Since genuine OSHA recognized laminated plank is mechanically tested and the structural integrity is more predictable, cutting longer boards into shorter ones is generally not an issue. Keep in mind that older, used planks may have been compromised from prior usage and field conditions, and therefore should be inspected closely before cutting.