Questioning Safety: Scaffolding #2 – Purpose, Use & Design
What is the scaffold’s purpose, use, and design?
The first step in evaluating any scaffold is to get a thorough understanding of its purpose, usage, and design. Without this knowledge, it is impossible to assess the structure and its safety correctly.
What is the purpose of the scaffold?
Consider the following three scaffolds:
- An inspection scaffold to be used by a technologist to visually check for conveyor damage.
- A welding scaffold for a shipyard ironworker working on a very large and time-consuming seam.
- A shutdown scaffold to be occupied by four millwrights with hundreds of pounds of tools, materials, and equipment.
All three would be very different scaffolds with very different priorities!
The “inspection scaffold” might only need to be light duty with a narrow platform directly in visual range of the conveyor.
The “welding scaffold” would need a heavier duty and larger size to accommodate welding materials and equipment. However, the precise height of the working platform would be crucial to the welder. They will want to comfortably reach the seam for the long weld.
The “shutdown scaffold” would require a much more substantial duty rating and size to accommodate the live loads. It may also require special preparation to accommodate “point loads” caused by heavier materials or equipment.
Does the scaffold require engineering?
Under many regulations and standards, there are rules that can trigger the need for additional engineering design. These rules also vary by jurisdiction, but generally involve scaffolds with one or more of the following characteristics:
- Very tall scaffolds (typically over 50 feet or 15 meters tall)
- Scaffold platforms rated for more than “Heavy Duty” (75 pounds per square foot or 367 kilograms per square meter)
- Enclosed Scaffolds
- Hanging Scaffolds
- Scaffolds with cantilevered platforms
- Scaffolds with motorized hoisting devices
- Outrigger or truss scaffolds
- Scaffolds erected on engineered structures (e.g., rooftops, grated surfaces, etc.)
Who can engineer scaffolds?
All engineers must follow a professional code of ethics to only provide engineering services in their area of specialization.
More scaffold design engineers are needed in this growing industry. There are only a few professional engineering firms that have engineers and designers experienced with scaffolding systems.
In some cases, the engineering required may only be minor, such as a tie design for a cantilever, or an assessment of a rooftop foundation. However, in other cases, a complete, detailed scaffold design may be required – such as for a hanging scaffold or a large exterior enclosed scaffold.
What should engineered scaffold design drawings show?
A complete, detailed scaffold design should clearly show multiple elevations, plan view(s), section(s) and details. Scaffold components must also be clearly identified on the drawings. Drawing notes must also indicate design load ratings, inspection instructions, and the applicable regulations and standards. Any deviance from the engineered scaffold design may be done ONLY with the written permission of the design engineer.
- How do we identify and communicate the scaffold’s purpose and use from planner-to erector-to inspector-to user?
- Do the scaffold erectors always have a thorough understanding of the scaffold’s purpose and usage?
- Do we have a formal (on paper) scaffold requisition and handover process?
- Do we differentiate between “distributed loading” and “point loading” in the scaffold planning process?
- What guidance do we follow in deciding if a scaffold requires engineering?
- Who decides if the scaffold requires any special engineering?
- If required, what is the process of getting a scaffold engineered for our site?
- Are our scaffold erectors able to read engineered design drawings?
- Do we have a means of identifying engineered scaffolds on our scaffold tags?
- Are we using design engineers who are suitably trained and experienced in designing scaffolding?