Scaffold General Requirements
Scaffolds that will be greater than 125 feet in height above their base plates must be designed by a registered professional engineer (i.e. a qualified person).
Lean-to scaffolds are prohibited. Lean-to scaffolds are supported by tilting it toward and resting upon a building or structure.
Shore scafffolds are prohibited. Shore scaffolds are placed against a building or structure and are held in place with props.
When preparing for work involving scaffolding, it is important to consider the following:
- What will be the intended use of the scaffolding? Consider what work tasks will be performed, anticipated loads for people, materials, and equipment, any unique building configurations which may create a problem, and electrical or piping obstructions which are in the area.
- What are the site conditions? Will the scaffolding be set up on a concrete foundation, pavement/asphalt, or earth? If set up on earth, what class of soil is present and is the area level? Are there weather conditions to consider?
- How high will the scaffolding be and will it need to be secured to the building structure or designed by a qualified person?
- Will pedestrians be affected? Building accesses must be maintained and overhead protection may be required.
Maximum Intended Load
Each scaffold and scaffold component shall be capable of supporting, without failure, its own weight and at least four times the maximum intended load applied or transmitted to the scaffold. To figure the maximum intended load, total the weight of all persons, equipment, tools, materials, transmitted loads, and other loads reasonably anticipated to be applied to the scaffold (or scaffold component) at any one time. (Persons are estimated at 250 pounds each.)
- Example 1: The work to be performed will require two persons (250 pounds each), 10 pounds of hand tools, and 50 pounds of materials, for a total of 560 pounds. The scaffolding selected must be able to withstand this load (the safety factor of four is designed into the rated load capacity).
Rated Load Capacity
Scaffold and scaffold components shall not be loaded in excess of their maximum intended load or rated capacity, whichever is less. The rated load capacity of a scaffold is defined below.
Rated Load Capacity of Scaffold
Intended Load Should Be
25 pounds per square foot
50 pounds per square foot
75 pounds per square foot
The maximum weight that can be applied to the scaffold is determined by data supplied by the manufacturer, expressed as permissible load per square feet (e.g. 25 psf, 50 psf, or 75 psf, multiplied by the square footage of the scaffold work surface.
- Example 2: The scaffold size is 7 feet long by 5 feet wide - a total square footage of 35 square feet. The type of scaffolding being used is rated as light-duty, or 25 pounds per square foot. Multiply 35 square feet by 25 pounds per square foot and the scaffolding can be loaded with no more than 875 pounds. Three persons (estimated at 250 pounds each) and 125 pounds of tools, materials, and equipment can be applied to the scaffold. A light-duty scaffold would therefore be adequate for the anticipated work described in Example 1 above.
A simple method to determine if a scaffold is overloaded is the Deflection Method. Platforms, planks, or decking must not deflect more than 1/60 of the span when loaded. The deflection is measured with a tape measure and a straight edge.
- Example 3: A scaffold has a plank that rests on supports 10 feet apart (i.e. a span of 10 feet or 120 inches). 120 inches multiplied by 1/60 equals 2 inches maximum deflection. If the bowing of the board under the weight applied to the plank exceeds two inches, the scaffold is overloaded.
When working or erecting scaffolding in the vicinity of overhead electrical lines, it is critical that minimum clearances be observed and/or that power lines are de-energized or insulated by the power company. Clearances apply to the tools and equipment being used in the vicinity of the power lines, materials being handled, any scaffolding component, and any part of a person's body. For clearance distances for insulated and uninsulated power lines, click here.
Employees shall be prohibited from working on scaffolds covered with snow, ice, or other slippery material (ex. mud), except as necessary to remove such materials. Work on or from scaffolds is also prohibied during storms or high winds unless a competent person has determined that it is safe for employees to be on the scaffold and those employees are protected by personal fall arrest systems or wind screens.
- Wind screens shall not be used unless the scaffold is secured against the anticipated wind forces.
- Where uplift can occur which could displace scaffold end frames or panels, they shall be locked together vertically with pins or equivalent.
Debris shall not be allowed to accumulate on work platforms. Scrap material, mortar, demolition materials, etc. shall be removed regularly in a safe and orderly manner.
Ladders or makeshift devices, such as boxes, barrels, chairs, cans, etc. shall not be used on top of scaffold platforms to increase the working level height of employees.
The scaffold competent person must inspect the scaffold before each shift and after any occurrence which could affect the integrity of the scaffold, such as being bumped by a vehicle, damaged, or excessive rain or freezing/thawing of the ground which could affect the foundation. Scaffolding should be inspected for visual defects, such as:
- Bent or damaged components
- Missing guardrails or crossbracing
- Proper access
- Unstable foundation
The scaffold competent person must be notified immediately if a component becomes damaged after erection, and the scaffold must not be used until the damaged component has been properly repaired or replaced.