Key Takeaways
- Supported scaffolds are built on the ground and come in standard lengths.
- When scaffolds reach a height-to-base ratio of 4:1 or greater, they must be restrained from tipping by OSHA-approved methods.
- All poles, legs, and uprights must bear on stable, adequate foundations.
Citations for violating scaffolding requirements consistently make it onto OSHA’s annual Top 10 list. The requirements are located in 29 CFR 1926.451(a) through (h). In this article, we look at the requirements for supported scaffolds [29 CFR 1926.451(c)].
What is a supported scaffold? It is one of two types of scaffold. The other type is a “suspended scaffold.” If you are now thinking that a suspended scaffold is obviously one that’s hanging from something above it — a supported scaffold must be one you build on the ground — then you are correct. You may have seen an example of a suspended scaffold by spotting a window washing operation on a skyscraper.
Supported scaffolds are constructed as needed for a specific task or set of tasks. It comes in standard lengths such as 6 ft, 8 ft, and 10 ft. Common frame heights include 3 ft, 5 ft, and 7 ft, plus 6 ft 4 in. is also common. They typically have a platform width of 29 in. (a double wide is 54 in.).
If you build the scaffold only a single tier in height, it’s very stable. Picture a steel frame box that is 6 feet long and 3 feet tall. It’s hardly going to tip over. But let’s say you need to reach a work area that is 25 feet from grade and use 3 sections of 7 ft tall frame (21 ft). That’s a ratio of 21:6 or 7:2. At 8:2 (4:1), the stability is reduced enough that a special rule kicks in. It must be restrained from tipping by guying, tying, bracing, or equivalent means [29 CFR 1926.451(c)(1)]. The particulars of those means are spelled out in 29 CFR 1926.451(c)(1)(i), (ii), and (iii). For example, you must install them where horizontal members support both inner and outer legs.
The poles, legs, posts, frames, and uprights must bear on base plates and mud sills or other adequate firm foundation [29 CFR 1926.451(c)(2)]. OSHA follows this requirement with five particulars. For example, you can’t use unstable objects to support scaffolding. You can’t use lift trucks or front-loaders for this purpose either, unless they meet the specific requirements stated in 29 CFR 1926.451(c)(2)(iv) and (v).
If you’ve ever watched a qualified person erect scaffolding, you’ve probably noticed the use of a couple of magnetic levels. That isn’t just for the aesthetics, it’s to prevent swaying and displacement. The poles, posts, frames, and uprights must be plumb [29 CFR 1926.451(c)(3)].
About the Author
Mark Lamendola
Mark is an expert in maintenance management, having racked up an impressive track record during his time working in the field. He also has extensive knowledge of, and practical expertise with, the National Electrical Code (NEC). Through his consulting business, he provides articles and training materials on electrical topics, specializing in making difficult subjects easy to understand and focusing on the practical aspects of electrical work.
Prior to starting his own business, Mark served as the Technical Editor on EC&M for six years, worked three years in nuclear maintenance, six years as a contract project engineer/project manager, three years as a systems engineer, and three years in plant maintenance management.
Mark earned an AAS degree from Rock Valley College, a BSEET from Columbia Pacific University, and an MBA from Lake Erie College. He’s also completed several related certifications over the years and even was formerly licensed as a Master Electrician. He is a Senior Member of the IEEE and past Chairman of the Kansas City Chapters of both the IEEE and the IEEE Computer Society. Mark also served as the program director for, a board member of, and webmaster of, the Midwest Chapter of the 7x24 Exchange. He has also held memberships with the following organizations: NETA, NFPA, International Association of Webmasters, and Institute of Certified Professional Managers.