Swing scaffolds should be suspended by wire or fiber line secured to the outrigger beams, A minimum safety factor of 6 is required for suspension ropes, The blocks for fiber ropes should be the standard 6-inch size consisting of at least one double block and one single block. The sheaves of all blocks should fit the size of rope used.

The outrigger beams should be spaced no more than the hanger spacing and should be constructed of no less than 2-by-10 lumber. The beam should not extend more than 6 feet beyond the face of the building. The inboard side should be 9 feet beyond the edge of the building and should be securely fastened to the building.

Figure 4-43 shows a swinging scaffold that can be used for heavy work with block and tackle.

POLE SCAFFOLD CONSTRUCTION

The poles on a job-built pole scaffold should not exceed 60 feet in height. If higher poles are required, the scaffolding must be designed by an engineer.

All poles must be setup perfectly plumb.

The lower ends of poles must not bear directly on a natural earth surface. If the surface is earth, a board footing 2-inches thick and 6- to 12-inches wide (depending on the softness of the earth) must be placed under the poles.

If poles must be spliced, splice plates must not be less than 4-feet long, not less than the width of the pole wide, and each pair of plates must have a combined thickness not less than the thickness of the pole. Adjacent poles must not be spliced at the same level.

A ledger must be long enough to extend over two pole spaces, and it must overlap the poles at the ends by at least 4 inches. Ledgers must be spliced by overlapping and nailing at poles - never between poles. If platform planks are raised as work progresses upward, the ledgers and logs on which the planks previously rested must be left in place to brace and stiffen the poles. For a heavy-duty scaffold, ledgers must be supported by cleats, nailed or bolted to the poles, as well as by being nailed themselves to the poles.

A single log must be set with the longer section dimension vertical, and logs must be long enough to overlap the poles by at least 3 inches. They should be both face nailed to the poles and toenailed to the ledgers. When the inner end of the log butts against the wall (as it does in a single-pole scaffold), it must be supported by a 2-by-6-inch bearing block, not less than 12 inches long, notched out the width of the log and securely nailed to the wall. The inner end of the log should be nailed to both the bearing block and the wall. If the inner end of a log is located in a window opening, it must be supported on a stout plank nailed across the opening. If the inner end of a log is nailed to a building stud, it must be supported on a cleat, the same thickness as the log, and nailed to the stud.

Figure 4-43. - Swinging scaffold.

A platform plank must never be less than 2-inches thick. Edges of planks should be close enough together to prevent tools or materials from falling through the opening. A plank must be long enough to extend over three logs, with an overlap of at least 6 inches, but not more than 12 inches.

PREFABRICATED SCAFFOLD ERECTION

Several types of scaffolding are available for simple and rapid erection, one of which is shown in