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.

November 25, 1997

Mr. Stephen Almony
Perini Corporation
217 South Burlington Road
Bridgeton, New Jersey 08302

Dear Mr. Almony:

This is in response to your fax transmission of September 4 to the Occupational Safety and Health Administration (OSHA) in which you asked about the Agency's interpretation of several issues that had been addressed in OSHA Program Directive #100-84, dated January 31, 1978. As you noted, those interpretations applied to the old scaffold standard for construction, which was revised in August of 1996. We appreciate your taking the time to communicate with the Agency.




  1. Regarding superseded 29 CFR 1926.451(a)(2)-The interpretation stated that the "concrete block is not always an 'unstable object' when used as a base for scaffolding. The circumstances and techniques under which it is used must be considered to determine its stability." In the revised standard, the provision barring the use of unstable objects to support scaffolds has been moved to §1926.451(c)(2)(ii). Although the revised provision no longer provides specific examples of unstable objects, this interpretation from 1978 remains true under the revised standard. However, hollow-core masonry units would never be acceptable to support scaffolds.
  2. Regarding the superseded bracing requirements (please note, the 1978 reference to 29 CFR 1926.451(a)(3) is incorrect, but bracing is required by several other provisions) -- The interpretation stated that "A brace is defined in 29 CFR 1926.452(b)(3) as a tie that holds one scaffold member in a fixed position with respect to another member. The fact that a scaffold member has a place for a brace does not necessarily require that the brace be in place, if it interferes with the erection or stocking of the scaffold. This is only true if the scaffolding is capable of supporting four times the maximum intended load and meets the other applicable requirements of 29 CFR 1926.451. Also, the manufacturer's design specifications, particularly with respect to the lateral stresses involved, are an important aspect that must be considered in the decision to remove pieces of bracing."

    In the revised standard, the definition of the term "brace" has been changed editorially by replacing the word "tie" with "rigid connection," but the above interpretation is still true provided that a competent person approves the scaffold design. In the revised standard, the provision that scaffolds shall be capable of supporting four times the maximum intended load has been moved to §1926.451(a)(1).

  3. Regarding superseded 29 CFR 1926.451(a)(7) and (8) -- The interpretation stated that "A scaffold plank is considered a component of the scaffolding. As such, it must be capable of supporting four times the maximum intended load without failure (a safety factor of four.) The fact that a plank might have a split in one end does not automatically mean that it must be removed from service, provided it does not otherwise create a hazard to the employees."

    As noted above in our answer to b., the revised standard redesignated the provision that scaffolds shall be capable of supporting four times the maximum intended load to §1926.451(a)(1). The provision that damaged or weakened scaffold components shall be immediately replaced or repaired was amended in the revised standard, and redesignated to §1926.451(f)(4). Revised paragraph (f)(4) addresses scaffold use and references back to the scaffold strength requirements in paragraph (a)(1). The interpretation above from 1978 is still valid under the revised standard with the approval of a competent person.

  4. Regarding superseded 29 CFR 1926.451(d)(4) -- The interpretation stated that scaffold legs are required "to be placed on a foundation that is adequate to support four times the intended load of the scaffold. The standard does not require that base plates always be employed, but only when conditions necessitate their use. For example, the scaffold legs cannot be placed on a mud foundation without a base to prevent the legs from sinking into the mud."

    In the introductory text to §1926.451(c)(2), the revised standard requires base plates (and mud sills or other adequate firm foundation) at all times now for support scaffold poles, legs, posts, frames, and uprights.

Should you require further assistance, please do not hesitate to contact us again by writing to: OSHA Directorate of Construction, Office of Construction Standards and Compliance Assistance, Room N3621, Washington D.C., 20210.


Roy Gurnham, Director
Office of Construction Standards and Compliance Assistance