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Standard Interpretations - Table of Contents
• Standard Number: 1926.451(g); 1926.451(h); 1926.452(w)

OSHA requirements are set by statute, standards and regulations. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations. This letter constitutes OSHA's interpretation of the requirements discussed. Note that our enforcement guidance may be affected by changes to OSHA rules. Also, from time to time we update our guidance in response to new information. To keep apprised of such developments, you can consult OSHA's website at http://www.osha.gov.

June 9, 2000

Mr. Paul Schnitzler
RG Insulation
2505 East 74th Avenue
Denver, CO 80229

RE: 1905.11(b)(4), 1926.451(f)(3) & (f)(7), 1926.451(g)(4)(ii), 1926.451(g)(4)(iv), 1926.451(g)(4)(ix), 1926.452(w)(2) & (w)(3), 1926.452(w)(6)(ii), 1926.452(w)(6)(iii), Subpart L Appendix A, Scaffold Toprails, Scaffold Midrails, Moving Mobile Scaffolds, Outrigger Frames

Dear Mr. Schnitzler:

This is in response to your letter dated August 15, 1997, addressed to the Occupational Safety and Health Administration's (OSHA) Denver Regional Office in which you asked several questions regarding 29 C.F.R. 1926 Subpart L (Scaffolds). Unfortunately, we misplaced your letter and failed to recognize our error in a timely manner. We apologize for the extended delay in providing this response.

Question (1): Under §1926.451(g)(4)(ii), the minimum height for scaffold guardrails manufactured and first placed in service before January 1, 2000, is 36 inches. The minimum guardrail height for scaffolds manufactured or first placed in service after January 1, 2000 is 38 inches. For all scaffolds, the maximum height is 45 inches. You state that your scaffold extensions have rungs spaced 16 inches apart and that when using them, the only way of attaching guardrails is to the rungs. Therefore, when the scaffold board is on the bottom rung of the extension, the toprail has to be 16, 32, or 48 inches high (depending on which rung is used for attaching the guardrail). Is it permissible for to have a toprail height of 32 inches where the platform is small, the exposure time is limited, the same person who erects and dismantles the scaffold will be the one working on it, and a guardrail at 48 inches would interfere with the work surface in some instances?

Answer: Section 1926.451(g)(4)(ii) provides that, "when conditions warrant, the height of the top edge may exceed the 45-inch height, provided the guardrail system meets all other criteria of paragraph (g)(4)." However, the standard does not allow for a height of less than 36 inches. The reason for this is that a guardrail lower than 36 inches would be below the center of gravity of the average worker. A guardrail that is too low would not prevent the worker from falling off the scaffold. Therefore, if you cannot comply with the 45-inch maximum height, you may raise the toprail to 48 inches. Where that would interfere with the work surface, you would have to use a different kind of guardrail system then the one you are using so that you would not be limited by the rung spacing. Alternatively, you could use personal fall protection equipment instead of guardrails (as long as there is an adequate anchorage point).

Question (2): Section 1926.451(g)(4)(iv) requires midrails to be "installed at a height approximately midway between the top edge of the guardrail system and the platform surface." Is there a provision in the standard that directs when midrails must be used?

Answer: Under §1926.451, all employees on scaffolds more than 10 feet above the next lower level must be protected from falls. The standard requires guardrails for some specific types of scaffolds (see, for example, §1926.451(g)(1)(iv), which requires them for self-contained adjustable scaffolds; and §1926.451(g)(1)(v), which requires them for each employee on a walkway located within a scaffold). With respect to protecting employees on all other types of scaffolds, under §1926.451(g)(1)(vii), the employer can choose to use either personal fall arrest systems or guardrail systems.

Whenever guardrail systems are used, they must meet the definition of a "guardrail system" in §1926.450(b), as well as the requirements of §1926.451(g)(4). The standard's definition of a guardrail system is: "a vertical barrier, consisting of, but not limited to, Toprails, midrails, and posts, erected to prevent employees from falling off a scaffold platform or walkway to lower levels [emphasis added]." Therefore, guardrail systems must have midrails. Under Section 1926.451(g)(4), screens, mesh, intermediate vertical members, solid panels and equivalent structural members may be substituted for midrails as long as they meet the requirements in (g)(4).

Question (3): Is the purpose of the midrail requirement limited to providing protection from falling objects?

Answer: No. The purpose of the requirement is to prevent an employee from falling. Consequently, the strength requirements in (g)(4) for midrails and their substitutes are designed to ensure that a worker will not fall through (see Volume 61 of the Federal Register at page 46,072].

Also, in §1926.451(h), the standard requires the employer to protect employees from falling objects. That provision gives employers several choices with respect to how to accomplish that. One of those choices is to use a guardrail system. If you choose to use a guardrail system to provide this protection, §1926.451(h)(iv) requires that its "openings [be] small enough to prevent passage of potential falling objects."

Question (4): You assert that it is common industry practice that employees on top of the scaffold propel it by pulling or pushing against walls, ceilings, etc. to avoid having to repeatedly get on and off the scaffold. You ask if the standard prohibits this.

Answer: Sections 1926.452(w)(2), (w)(3), and (w)(6) address this issue. These sections provide:
(w)(2): Scaffold casters and wheels shall be locked with positive wheel and/or wheel swivel locks, or equivalent means, to prevent movement of the scaffold while the scaffold is used in a stationary manner.

(w)(3) Manual force used to move the scaffold shall be applied as close to the base as practicable, but not more than 5 feet (1.5 m) above the supporting surface.

(w)(6) Employees shall not be allowed to ride on scaffolds unless the following conditions are met:
(i) The surface on which the scaffold is being moved is within 3 degrees of level, and free of pits, holes and obstructions;
(ii) The height-to-base width ratio of the scaffold during movement is two to one or less, unless the scaffold is designed and constructed to meet or exceed nationally recognized stability test requirements such as those listed in paragraph (w) of appendix A to this subpart (ANSI/IA A92.5 and A92.6)
(iii) Outrigger frames, when used, are installed on both sides of the scaffold;
(iv) When power systems are used, the propelling force is applied directly to the wheels, and does not produce a speed in excess of 1 foot per second (.3 mps) and
(v) No employee is on any part of the scaffold which extends outward beyond the wheels, casters of other supports.
An employee propelling the scaffold while on it is considered to be riding the scaffold. In view of these requirements, it would be permissible to have employees on the scaffold propel it under the following circumstances: (1) The employees on the scaffold could lock and unlock the casters while on the scaffold; (2) the employees' feet were no more than 5 feet above the surface that supports the scaffold, and that is as close to the base of the scaffold as is possible to apply force; and (3) all of the requirements of (w)(6) were met.

You requested a permanent variance from these provisions (specifically, from (w)(2) (locking the scaffold's casters and wheels if the scaffold is stationary and in use); (w)(3) (moving the scaffold manually by applying force to the scaffold at a point no more than 5 feet above the supporting surface); and (w)(6)(ii) (the requisite height-to-base width ratio of the scaffold during movement). The purpose of these requirements is to prevent a mobile scaffold from becoming unstable and overturning while employees are moving it and/or on it.

Section (6)(d) of the Occupational Safety and Health Act of 1970 and paragraph (b)(4) of 29 CFR §1905.11 require that your proposed alternative must protect employees at least as well as the existing OSHA requirements. To be eligible for a variance, therefore, you must demonstrate that your alternative provides your employees with a level of safety that is at least equal to the level of safety if you met the OSHA requirements.

In your proposed alternative, employees located at the top of a mobile scaffold would propel it by using their arms and hands to push/pull against rafters, trusses and walls under eight specified conditions. These conditions relate primarily to ensuring a safe support surface for the scaffold -- one that is free of such things as obstacles, inclines, holes, and vents. Ensuring a safe support surface does not address the fact that scaffolds can overturn even on safe support surfaces. Scaffolds that are top-heavy, or that are pushed too far above their base, or in other respects fail to meet the requirements in §1926.452(w), can topple. The standard's requirements regarding the maximum height-to-base width ratio apply in addition to, not as a substitute for, the requirements for a safe support surface.

Your proposed alternative would not be as safe because the measures you list are already required and do not address hazards dealt with by the remainder of the standard's requirements. The proposed alternative would therefore increase the risk of injury. Accordingly, we must deny your request for a permanent variance from the requirements for mobile scaffolds specified in paragraphs (w)(2), (w)(3), and (w)(6)(ii) of CFR 1926.452.

However, we would be happy to work with you to try to come up with some constructive suggestions for dealing with the problems you have described. I have asked Mr. Louis Rowe of my staff to discuss your particular situation with you and to see if members of the scaffold industry have some equipment solutions.

Question (5): You assert that the height-to-base ratio requirement of 2-to-1 in Section 1926.452(w)(6)(ii) is inappropriate and state that it instead should be 3 to 1.

Answer: Section 1926.452(w)(6)(ii) provides: "the height-to-base width ratio of the scaffold during movement is two to one or less, unless the scaffold is designed and constructed to meet or exceed nationally recognized stability test requirements." The issue of what ratio should be required was addressed during the rulemaking process as explained in the preamble to the standard. [Volume 61 of the Federal Register, Page 46,091]. In fact, a number of commenters to the proposed rule, as well as the Advisory Committee for Construction Safety and Health (ACCSH), advocated that OSHA prohibit riding scaffolds. Ultimately, the Agency determined that, with appropriate safeguards -- including the 2-to-1 ratio -- the practice should be allowed. In addition, the standard allows higher ratios where the scaffold is designed and constructed to meet or exceed nationally recognized stability test requirements.

Question (6): When the installation of the scaffold outrigger frames in one or more of the corners is difficult, may the scaffold be used without them? Additionally, if the jobsite conditions do not allow full compliance with the outrigger requirements, would partial or non-compliance be permitted under the following circumstances?
  1. When conditions allow, two outriggers will be installed, one at each opposing corner and opposing side of scaffold.
  2. Where conditions allow, two outriggers will be installed, one at each side on one end of the scaffold.
  3. If conditions do not allow installation of outriggers as described in (1) and (2), the scaffold will be used without them, in which case rolling the scaffold will be prohibited and the wheels will be locked.
Answer: Section 1926.452(w)(6)(iii) provides that, "outrigger frames, when used, are installed on both sides of the scaffold." The standard generally does not permit omitting outrigger frames, even when they are difficult to install. That is because the outriggers normally are crucial equipment for preventing the scaffold from overturning. However, in some cases, scaffolds that require outriggers under the standard can be constructed so that the scaffold will be sufficiently stable without them. In short, outriggers may be omitted if the requirements of the standard's non-mandatory Appendix A are met.

Appendix A, Section (w), references stability tests that are described in the ANSI A-92 aerial lift series documents.
1 If you conduct these tests and they demonstrate the intended configuration of the scaffold passes them without the outrigger frames, the outrigger frames may be omitted.

Send future inquiries to: [Office of Construction Standards and Guidance USDOL/OSHA Room N3468, 200 Constitution Avenue, N.W. Washington, D.C. 20210 at (202) 693-2020]


Russell B. Swanson, Director
Directorate of Construction

[Corrected 05/28/04]

1 If you need a copy of these documents, contact ANSI at 202-293-8020.
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Standard Interpretations - Table of Contents

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