Masonry Magazine October 1998 Page. 21
It never ceases to amaze me how one of the most important pieces of equipment on a job site is so often taken for granted. It is hard to rationalize why scaffold plank is often viewed as just lumber when in fact it is much more. This so called lumber could make all the difference in one's fate. A scaffold system is only as effective as the sum of its components. Last September, the Occupational Safety and Health Administration (O.S.H.A.) implemented a new scaffold standard with hopes that safer practices would be exercised on the job. The "competent person" criteria was established and now contractors must appoint an employee to be responsible for identifying and resolving safety-related issues. So what should this "competent person" know about scaffold plank? If you analyze the new scaffold standard closely, you will discover O.S.H.A. does not endorse just any wood product for scaffold use. In general, there are two types of wood plank recognized, "solid sawn" and "manufactured" wood plank. Both types are acceptable and your appointed "competent person" should know why.
Proper Plank Selection and Care
Scaffolding Violations were the Second Largest OSHA Volations for Fiscal Year 1996
It is hard to rationalize why scaffold plank is often viewed as just lumber when in fact it is much more.
Solid Sawn Wood Plank
This type of plank has been around for many years and is still commonly used. Boards are cut from a specific portion of logs to minimize the inherent defects found in trees. There are primarily three wood species milled and graded for scaffold plank. Southern Yellow Pine (SYP) is harvested in the South, Douglas Fir (DF) in the Pacific Northwest, and Sitka Spruce (S) in northern Canada. The availability of these species of plank may vary depending upon your region of the country. Each specie has distinctly different structural properties and graded per the respective grading agency. Several factors such as slope-of-grain, moisture content, fiber bending value (Fb), and modulus of elasticity (MOE), predicate whether a "solid sawn" board is suitable for scaffold use. The "competent person" should understand that only a certified lumber grader can visually inspect boards and determine if worthy as "Scaffold Plank." It is extremely dangerous to assume a wood board is strong enough to support intended loads just because it has few knots and defects. A true scaffold plank should bare a stamp that indicates the specie of wood, respective grade, mill number, grading agency, and most importantly identify the board as "Scaffold Plank." See figure #1.
Solid Sawn Wood Plank
This type of plank has been around for many years and is still commonly used. Boards are cut from a specific portion of logs to minimize the inherent defects found in trees. There are primarily three wood species milled and graded for scaffold plank. Southern Yellow Pine (SYP) is harvested in the South, Douglas Fir (DF) in the Pacific Northwest, and Sitka Spruce (S) in northern Canada. The availability of these species of plank may vary depending upon your region of the country. Each specie has distinctly different structural properties and graded per the respective grading agency. Several factors such as slope-of-grain, moisture content,
Manufactured Wood Plank
In the late 70's, some wood product manufacture's realized the old growth, larger trees by which "solid sawn" lumber was milled, was becoming less plentiful. After considerable research and development, a new wood product emerged known as Laminated Veneer Lumber (LVL). Manufactured similar to plywood, LVL is comprised of wood veneers which are bonded with exterior adhesive. The difference is, LVL is laid-up with the wood grain in a unidirectional fashion, thus giving it optimal strength when on the flat. The result is a homogeneous lumber with predictable structural values. The knots and defects are dispersed throughout the entire product. In addition, LVL is environmentally friendly since its production method utilizes wood fiber most effectively. All things considered, laminated veneer lumber became an obvious choice for scaffold plank. Today, there are several LVL producers, but only a few are qualified to make laminated scaffold plank. The manufacturing process is similar for each but they differentiate their planks by using different wood species. Regardless, each manufacturer must produce plank to meet or exceed the 4:1 safety factor prescribed by O.S.H.A. As with "solid sawn" plank, laminated plank manufacturers must use an approved independent inspection agency and proof-load their product to ensure consistent quality.