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Height, bracing, and rails on mobile scaffold towers

Summary A scaffold manufacturer asked how construction rules applied to a mobile tower. OSHA said the photographed unit should be treated as one tower and meet the then-current height-to-base ratio, bracing, and guardrail requirements; it could not assess claimed stability from nearby racks without more information. OSHA archives the letter.
Document
Federal opinion letter
Agency
Occupational Safety and Health Administration (OSHA)
Document number
1981-06-25
Date issued
June 25, 1981
Status
Archived by the agency
OSHA labels this an archive document and warns that it may no longer represent OSHA policy.
Status last verified October 10, 2026

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NOTICE: This is an OSHA Archive Document, and may no longer represent OSHA Policy. It is presented here as historical content, for research and review purposes only.

June 25, 1981

Mr. Marshall Klarfeld
Product Safety Engineer
Up-Right, Incorporated
[Recipient address omitted]

Dear Mr. Klarfeld:

This is in response to your letter of June 12, 1981, requesting an interpretation on the use of mobile scaffold towers.

29 CFR 1926.451(e)(1) requires when free standing mobile scaffold towers are use, the height shall not exceed four times the minimum base dimension. 29 CFR 1926.451(d)(3) requires scaffolds to be properly braces by cross bracing or diagonal braces, or both, for securing vertical members together laterally, and the cross braces shall be of such length as will automatically square and align vertical members so that the erected scaffold is always plumb, square, and rigid. 29 CFR 1926.451(e)(10) requires guardrails made of lumber, not less than 2 x 4 inches (or other material providing equivalent protection), approximately 42 inches high, with a midrail, of 1 x 6 inch lumber (or other material providing equivalent protection), and toeboards, shall be installed at all open sides and ends on all scaffolds more than 10 feet above the ground or floor. The photograph attached to your June 12th, letter indicates non compliance with the above standards for manually propelled mobile scaffolds.

The unit shown in your photograph should considered a single tower and comply with all of the applicable requirements in 29 CFR 1926.451(e).

It is not possible for this office to evaluate any lateral stability provided by the storage racks because of the lack of specific information on this matter. However, the tower unit as indicated in the photograph must be braced as required in 29 CFR 1926.451(d)(3).

If we may be of further assistance, please call or write.

Sincerely,
John K. Barto Chief,
Division of Occupational Safety Programming

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