Workplace Safety Guides

   Types of Scaffolding

    

Compliance officers must be familiar with the requirements of the standards and pay special attention to the scaffolds when inspecting construction sites. To make it easier for compliance officers to target inspections toward the most likely areas of scaffold failure, it's helpful to look at how some of the more familiar types of scaffolds should be constructed.

Let's first look at the tubular metal frame scaffold, the most popular and widely used type of scaffold found on construction sites today. The tubular welded or fabricated scaffold is a sectional frame type scaffold consisting primarily of in-frames and cross braces.

Scaffolds must be properly braced by cross bracing to secure the vertical members laterally and must be of such length as to automatically square and align the vertical members. Proper cross bracing will also insure that the erected scaffold is plumb, square, and rigid.

Scaffold legs are either set on adjustable or plain bases, which are placed on mud sills or other foundations, to adequately support the maximum intended load. If built more then one section high, the scaffold frames must be placed one on top of the other with stacking pins to provide proper vertical alignment of the legs.

Where uplift may occur due to wind loads or hoisting operations, make sure that the end frames or sections are locked together. When erecting scaffolds, the vertical height must not exceed four times the minimum base dimension. If the height exceeds the four to one ratio, the scaffold must be tied to the building or structure at each end and at intermittent intervals, not to exceed 30 feet horizontally and 26 feet vertically. Outriggers can also be used to broaden the base and stabilize the scaffold to provide stability. To prevent lateral movement it is a good practice to secure all scaffolds to the building or structure at intervals of 25 to 30 feet horizontally and 25 feet vertically.

Drawings and specifications for all frame scaffolds more then 125 feet in height above the base plates must be designed by a registered professional engineer and copies of the plans made available to the compliance officer for inspection purposes.

Since there are several manufacturers of metal frame scaffolds, the mixing of components or individual member pieces is not recommended but is allowed if the end frames match, the cross members match, and stability and plumbness are maintained. In no case shall there be any modifications made of any components, nor shall they be forced to fit.

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