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 https://www.osha.gov.



February 1, 1999

Steven J. Hess
Sr. Safety Manager
CECO Concrete Construction, L.L.C
P.O. Box 28570
Kansas City, MO 64188

Re: 29 CFR 1926.502(b)(1)

Dear Mr. Hess:

Thank you for your letter dated July 1, 1998, to the Occupational Safety and Health Administration (OSHA) requesting clarification of 29 CFR 1926.502(b)(1) (guardrail height) as it applies to cast-in-place concrete structures. In your letter, you provide an example of a situation where employees perform work at a site that has two walking/working surfaces of different elevations (see attached diagram A). The lower elevation surrounds the higher elevation. You state that your company has a policy of placing guardrails on both surfaces if the height difference between the two elevations exceeds six feet. However, where the height difference is less than six feet, you do not put a guardrail on the upper surface. Instead, you use the guardrail on the lower surface to protect workers on the upper surface. You have a method for determining how high that lower lever guardrail needs to be to protect the upper level workers. You ask if your method meets OSHA requirements.

Your method is as follows: if the height difference of the upper and lower level is the same or less than the width of the lower level, you use a standard 42-in. guardrail. If the height of the upper level is more than the width of the lower level, you raise the guardrail high enough so that the top of the guardrail is 42 in. above the upper level.

A critical factor in using guardrails is to ensure that the top rail contacts employees above their center of gravity (approximately the mid section), thus preventing employees from pivoting over the guardrail. Your method does not ensure that this will always happen. For example, when the lower surface width and the height difference are equal, say 30 in., a guardrail of 39 in. (lowest allowed by OSHA) on the lower surface would not provide proper protection to employees working on the upper surface. Using the example of 30 in., employees working on the upper surface, with a 39-in. guardrail on the lower surface, would only receive the equivalent protection of a 31.3-in. guardrail erected on the upper surface (see attached diagram B). This is because a falling employee's arc of travel would cause the top rail to hit the employee at 31.3 in. on their body, thus placing their center of gravity above the top rail. In order to provide the proper fall protection to employees on the upper surface, you would need to raise the guardrail on the lower surface to 53.5 in.

To account for the arc of travel and ensure that the guardrail meets the employee above their center of gravity, measure the distance from the outer edge of the upper work surface to the top of the lower level guardrail. If you measure a distance less than 39 in., you need to increase the railing height enough to make this distance at least 39 in. If you measure 39 in. or more, then you do not need to raise the railing height (see attached diagram B). When raising the railing height, you may need to add a second mid-rail, at 42 in. (+/- 3 in.), to the guardrail so employees working on the lower surface will receive proper fall protection.

For further assistance, 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.]


Russell B. Swanson, Director
Directorate of Construction

[Corrected 09/5/2006]