June 21, 2004

Mr. Randy Wheeler
F & H Insulation, Inc.
P.O. Box 550
5003 E. 61^st Street N.
Kechi, KS 67067

Re: Whether plywood may be used to make platform decking for scaffolds under Part 1926 Subpart L (Scaffolds), and if so, whether the information in Table 7-3 of American Concrete Institute Committee SP-4 Formwork for Concrete (Fourth Edition) can be used as a guide in designing scaffold platforms? §1926.451(a)(1) and 1926.451(6), 1926.451(b), and 1926.451(f)

Dear Mr. Wheeler:

This is in response to your letter dated March 3, 2004, to the Occupational Safety and Health Administration (OSHA). You ask about the requirements in 29 CFR Part 1926 Subpart L (Scaffolds) regarding the use of plywood to make platform decking for scaffolds. Your letter was forwarded to this office for handling on April 1, 2004.

We have paraphrased your questions as below:

Question (1)(a): In the course of building supported scaffolds (such as tube-and-coupler), our construction company sometimes uses plywood to build large area scaffolds, as well as to cover gaps in scaffolds that result from protruding pipes and structures. Do OSHA standards prohibit the use of plywood as a platform decking material?

Answer:
It is permissible under certain conditions to use plywood as platform decking material. OSHA's construction industry standards addressing scaffolds are in 29 CFR Part 1926 Subpart L.

"Platform[s]," which form the working surfaces of scaffolds, are defined in §1926.451(b). That definition, in part, provides:

Platforms can be constructed using individual wood planks, fabricated planks, fabricated decks, and fabricated platforms. [Emphasis added.]

Section 1926.450(b) defines "Fabricated decking and planking" as:

manufactured platform[s] made of wood (including laminated wood, and solid sawn wood planks), metal or other materials. [Emphasis added.]

General scaffold requirements are set forth in §1926.451. Significantly, §1926.451(a)(1) states:

Capacity. Except as provided in ..., each scaffold and scaffold component shall be capable of supporting, without failure, its own weight and at least 4 times the maximum intended load applied or transmitted to it.

Section 1926.451(a)(6) continues:

Scaffolds shall be designed by a qualified person and shall be constructed in accordance with that design.

"Qualified" is defined in §1926.450(b) as:

... one who, by possession of a recognized degree, certificate, or professional standing , or who by extensive knowledge, training, and experience, has successfully demonstrated his/her ability to solve or resolve problems related to the subject matter, the work, or the project.

Additional criteria specific to scaffold platform construction are included in §1926.451(b) and address, among other items, spacing between units, walkway width, platform attachment and finishes.

Finally, §1926.451(f) contains, among others, the following Use requirement:

(16) Platforms shall not deflect more than 1/60 of the span when loaded.

Thus, by their terms, these provisions allow for the use of plywood, a fabricated decking or planking material, in the construction of platforms used in scaffolds.

However, employers must also ensure that such scaffolds are designed, erected, used and maintained in compliance with the relevant provisions of Subpart L. This includes selecting plywood that, when employed as a component in the design specifications of a scaffold, meets the above noted performance requirements relative to load-bearing capacity and deflection. To use plywood, the qualified person selected by the employer to design the scaffold system would have to know the technical aspects associated with planking and decking, including those that pertain to the strength and structural integrity of the individual scaffold components as well as the scaffold as a whole.

As concluded in the Preamble of Subpart L at 61 FR 46036 (August 30, 1996):

... materials quality is only one of several factors which must be considered when erecting a scaffold platform.

Question (1)(b): A compliance officer stated that plywood could only be used if it was "OSHA-approved plywood" -- is that right (and is there such a type of plywood?)

Answer:
Subpart L does not require that scaffold planks be graded and stamped by a qualified grading agency, nor does it require OSHA to approve any planking material. Therefore, OSHA does not "approve" any particular type of plywood to be used in forming a scaffold deck, just as it does not approve any other material. It is the responsibility of the employer to ensure that whatever material is used meets the requirements of Subpart L.

Question (2): As indicated above, we would like to continue to use plywood in the construction of our large area scaffolds, as well as to fill in the gaps. We use ¾-inch plywood with supports that are no more than 2 feet (on center) apart to build our large area scaffold decks. Similarly, we use ¾-inch plywood nailed to planks to cover the gaps, which range in length from 2 inches to 14 inches.

Is it permissible for the qualified person, designing our scaffold system, to use Table 7-3 of the American Concrete Institute Committee ("ACI") -- SP-4 Formwork for Concrete (Fourth Edition) as a starting point for the design?

Answer:
The Table you submitted is titled, "Table 7-3: Safe Spacing in Inches of Supports for Plywood Sheathing, Continuous over Four or More Supports" ("Table"). That Table, intended for use in the construction of concrete formwork, shows the maximum load for specified spans of varying thickness of Group 1 plywood E. As the title of the Table indicates, the calculations in that design table are dependent upon the use of continuous plywood sheathing over four or more supports. Assuming construction as indicated, the Table indicates a "maximum deflection 1/360 of span, but not more than 1/16 in."

Subject to the limitations noted in this answer, as a practical matter, the Table may be used as a starting point in locating supports and selecting the type, thickness and dimensions of plywood used to construct a scaffold platform.¹

However, several points must be emphasized. First, due to the limited strength of plywood, the distance between supports is critical. Note that almost all of the Table is based on using supports that are no further apart than 2 feet (on-center). In addition, our understanding is that the information in the Table is valid only if the plywood is oriented so that the grain of its outer (top and bottom) plies runs perpendicular to the supports.

Similarly, the Table's predictions of deflection under the specified parameters should also be generally reliable, particularly with regard to the construction of your large area scaffolds, as long as the Table's parameters are followed (assuming all the components of the complete system meet the scaffold design, assembly and used criteria in Subpart L). However, the Table's predictions of deflection may not be reliable in the construction of platforms to bridge gaps because the deflection of a single span used to fill in a gap will vary considerably from that of a continuous span.

With regard to using plywood to fill 2-inch to 14-inch gaps in your scaffold decks, again as a practical matter, it is unlikely that the requirements in Subpart L could be met unless the qualified person:

(1) Made an initial determination that the scaffold, apart from the gap, meets the scaffold design, assembly and used criteria set forth in Subpart L.

(2) Uses the Table (or a similar type of reference tool) as a guide in designing the plywood patches that cover the gaps.

(3) Has the plywood nailed or otherwise secured to the scaffold planks to prevent uplift.

(4) Considers the effect of the weight of the plywood on the planking and on the ultimate allowable load.

(5) Confirms that the complete scaffold, as repaired with the plywood, meets the requirements of Subpart L.

If you need additional information, please contact us by fax at: U.S. Department of Labor, OSHA, Directorate of Construction, Office of Construction Standards and Guidance, fax #202-693-1689. You can also contact us by mail at the above office, Room N3468, 200 Constitution Avenue, N.W., Washington, D.C. 20210, although there will be a delay in our receiving correspondence by mail.

Sincerely,


Russell B. Swanson, Director
Directorate of Construction

¹ We emphasize that the Table values are only a starting point because Subpart L requires the design to incorporate a 4:1 safety factor. [ back to text ]