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Standard Interpretations - Table of Contents
• Standard Number: 1926.451; 1926.451(e); 1926.451(e)(6); 1926.451(e)(6)(i); 1926.451(e)(6)(ii); 1926.451(e)(6)(iv); 1926.451(e)(6)(vi); 1926.451(e)(7)

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

March 14, 2002

Mr. Justin Breithaupt
Non-Stop Scaffolding, Inc.
1314 Hoadley Street
Shreveport, LA 71104

Re: Non-Stop scaffolding access frames; §1926.451(e)(6) and (7)

Dear Mr. Breithaupt:

This is in response to your letter of June 5, 2001, addressed to Dale Cavanaugh, OSHA Region X, requesting OSHA "provide input …to help keep [Non-Stop Scaffolding platform access] safe." The Region forwarded your letter to the Directorate of Construction for response. We apologize for the long delay in responding.

For clarity, your concerns have been rephrased as the following question: Do the integral, prefabricated access frames of Non-Stop Scaffolding, Inc. ["Non-Stop"] scaffold towers comply with OSHA requirements?

Non-Stop scaffold towers do not comply with OSHA's integral prefabricated scaffold access frame or ladder/stairway type access requirements.


In your letter, you refer to two horizontal brace "openings" in the Non-Stop scaffold tower structure, and to requirements in §1926.451(e)(6) for integral scaffold access frames. Although no engineering drawings were included with your letter, you included descriptive information about Non-Stop scaffold tower configurations and dimensions as well as illustrations ("Non-Stop materials"). This response is based on the Non-Stop materials provided in your letter.

It appears from the Non-Stop materials that your scaffold towers are comprised of a 9-foot tower base section and one or more 9-foot extension sections. Apparently, 4-foot 6-inch extension sections are also available. We assume that these short sections are similarly configured and are used atop base tower or extension sections.
Scaffold TowerScaffold Tower Section
As described, Non-Stop scaffold sections are built using a ladder-type frame with horizontal braces. The braces are spaced 9 inches apart vertically. These braces are 12 inches long and run between the scaffold section's vertical rails. Every 4'-6" vertically there is a diagonal tubular truss welded into the opening between horizontal braces. Judging from the illustrations, tubular trusses fall approximately at the middle and top openings of each scaffold section.

At the top of each section there is additional vertical and diagonal bracing between the truss and the horizontal brace. This additional bracing appears to form the bottom anchor for bolting the sections together. Attached to the bottom brace of all extension tower sections is a trident-shaped truss. The trident-shaped truss appears to form the top anchor for bolting sections together.

When sections are bolted one atop another, the trident-shaped truss obstructs the opening made between the top brace of the lower section and the bottom brace of the higher section. The other truss obstructs the opening directly below the one created by the joined sections.

From your illustrations, it appears the Non-Stop truss and trident-shaped truss configurations are different from each other in several ways. They intersect the top and bottom horizontal braces at different distances from the side rails. Also, they obstruct the openings between horizontal braces at different angles and different heights. Unobstructed space, either in the between-brace openings or on the horizontal braces, themselves, does not line up.

Lastly, the nut or bolt-head of the bolt holding sections together obstructs, to some extent, the brace opening and brace tread surface where it protrudes above its horizontal brace. This nut/bolt-head obstruction is midway between section side rails and gives less than 6 inches of tread to each side.

OSHA Regulation Part 1926 Subpart L Scaffolds

[§1926.451 General requirements.] (e) Access. . .
(6) Integral prefabricated scaffold access frames shall:

(i) Be specifically designed and constructed for use as ladder rungs;

(ii) Have a rung length of at least 8 inches (20 cm); . . .

(iv) Be uniformly spaced within each frame section; . . .

(vi) Have a maximum spacing between rungs of 16 3/4 inches. Non-uniform rung spacing caused by joining end frames is allowed, provided the resulting spacing does not exceed 16 3/4 inches.

(7) Steps and rungs of ladder and stairway type access shall line up vertically with each other between rest platforms.
As required by §1926.451(e)(6)(ii), the Non-Stop scaffold configuration provides more than 8 inches of tread on many of its horizontal braces. However, it does not provide a minimum rung length of 8 inches on many others. The configuration of the trusses appears to reduce the distance below 8 inches (i.e., the angle between the horizontal and diagonal legs effectively reduces the useable rung width to less than 8 inches). The section's joint truss and bolt create tread widths of less than 6 inches to each side rail. In addition, the truss shapes and nut/bolt-head obstructions violate §1926.451(e)(7), which requires vertical step/rung alignment.

Lastly, while it is also true that the standard allows irregular vertical rung spacing at end frame joints, the Non-Stop tower configuration creates a minimum vertical step of 36 inches between uniform horizontal braces. This 36 inches exceeds the OSHA requirement. Section 1926.451(e)(6)(vi) permits non-uniform spacing "provided the resulting spacing does not exceed 16 3/4 inches."

If you need additional information, please contact us by fax at: U.S. Department of Labor, OSHA, Directorate of Construction, [Office of Construction Standards and Compliance 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

Standard Interpretations - Table of Contents

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