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.

May 17, 1990

Richard F. Andree, CSP, PE, Ph.D. Executive Vice President Safety and Health Management Consultants, Inc. 161 William Street New York, New York 10038

Dear Mr. Andree:

This is in response to your letter of February 21, to Mr. Thomas J. Shepich, former Director of Compliance Programs, concerning our previous response of January 9, relative to the rung spacing between horizontal members of the end frames of metal scaffolds used as ladder rungs for access or egress. Please excuse the delay in our response.

The current standards of the Occupational Safety and Health Administration (OSHA) covering the issue of rung spacing on metal scaffolds specify a rung-spacing distance of 12 inches. However, further discussion of the issue is certainly appropriate. Unfortunately, the guidance provided by the standards of the American National Standards Institute, Inc. (ANSI) is somewhat confusing.

The OSHA standards, in this regard, were adopted from ANSI standards, as follows: 29 CFR 1910.28 from ANSI A10.8-1969, Safety Requirements for Scaffolding; and 29 CFR 1910.29 from ANSI A92.1-1971, Safety Requirements for Manually Propelled Mobile Scaffolds. The ladder standards at ANSI A14.3-1956, Safety Requirements for Fixed Ladders, were included by reference in both of the previously mentioned ANSI scaffold standards.

The ANSI A92.1 standard was withdrawn in October 1988 and the various technical responsibilities split between the ANSI A14 and A10.8 committees. Therefore, the present standards at ANSI A 14.3-1984 and ANSI A10.8-1988 must be evaluated to determine the present industry standard for acceptable access to scaffolds.

OSHA de minimis determinations are based, to a great extent, upon the acceptable industry practice as set forth by the applicable industry standards. In this instance, ANSI A10.8-1988, section 4.18, describes the presently accepted industry standard for safe access to scaffolds. That portion of the ANSI A10.8-1988 standard is enclosed.

ANSI A10.8-1988 permits scaffold frame members to be spaced at not more than 16 1/2 inches to achieve acceptable access to scaffolds. Although the ladder standards are more restrictive, and certainly the preferred standard, OSHA permits the use of maximum rung/frame spacing of 16 1/2 inches as a de minimis violation of the current OSHA standards at 29 CFR 1910.28 and 29 CFR 1910.29. The description of the OSHA de minimis violation policy is enclosed.

If we may be of further assistance, please contact us.


Patricia K. Clark Director Designate Directorate of Compliance Programs