SECTION III. SCAFFOLDING
CONSTRUCTION AND SAFETY
7-22. Extreme care should be taken in building scaffolds because lives depend on them. Use rough lumber for wood scaffolding. Never nail scaffolding in a temporary manner; always nail it securely. When you no longer need the planks at a lower level, remove them to avoid falling mortar splash.
TYPES OF SCAFFOLDING
7-23. A scaffold is a temporary, movable platform built with planks to support workers and materials. It allows bricklayers to work at heights not reachable when standing on the floor or ground. Scaffolds can be used in several functions and come in different sizes and heights.
7-24. Use a trestle scaffold shown in Figure 7-4 when laying bricks from the inside of a wall. Erect the scaffold when the wall reaches a height of 4 or 5 feet. The height of the trestles should range from 4 to 4 1/2 feet. The planks should be made using 2 by l0s. Place the trestle at least 3 inches from the wall so that it does not press against the newly laid bricks and force them out of line. Build the wall to the next floor level working from the scaffold. When the rough flooring for the next floor is in place, repeat the procedure.
Figure 7-4. Trestle scaffold
7-25. When reaching lower than a trestle scaffold permits, use a foot scaffold like the one shown in Figure 7-5. Place 2 by 10 planks on blocks supported by the trestle scaffold. A foot scaffold should not exceed 18 inches in height.
Figure 7-5. Foot scaffold
7-26. A putlog scaffold (see Figure 7-6) reaches from the ground to the height required. Its uprights are 4 by 4s supported on a 2 by 12 by 12 plank for bearing on the soil. Space the uprights on 8-foot centers and allow 4 1/2 feet of space between the wall and the uprights, as shown in Figure 7-6. The putlog is 3-by 4-inch lumber that spans the gap between the wall and the ledger. One end of the putlog rests on top of the ledger and against the 4 by 4 uprights, while the other end fits into the wall (one brick is omitted to make an opening for it). Do not fasten the putlog to the ledger. Place five 2 by 12 planks on top of the putlog to form the scaffold platform. Do not nail the planks to the putlog. Two ways to use stays are-
Tie the uprights to the wall with stays. You can either pass the stays through a window opening and fasten them to the inside structure or use spring stays as shown in Figure 7-6. To make spring stays, omit one brick from the wall and insert the ends of two 2 by 6s in the opening. Then insert a brick between the 2 by 6s and force the brick toward the wall. Bring the other ends of the 2 by 6s together and nail them securely to the ledger.
Use the putlog as a stay. You can also use the putlog as a stay by driving a wood wedge above the putlog into its hole in the wall. Then, nail the wedge to the putlog and nail the putlog to the ledger. Install longitudinal cross bracing as shown in Figure 7-6.
Figure 7-6. Putlog scaffold
7-27. An outrigger scaffold (see Figure 7-7) consists of a wood outrigger beam projecting from a window sill that supports 2 by 10 planks. Figure 7-7 shows how to brace a wood beam, but if you use a steel outrigger beam, fasten it to the structure's formwork using threaded U-bolts.
Figure 7-7. Outrigger scaffold
PREFABRICATED STEEL SCAFFOLD
7-28. If it is available, use prefabricated steel scaffolding (see Figure 7-8) rather than building a scaffold.
Figure 7-8. Prefabricated steel scaffold
7-29. Use a steel material tower if construction details are available because it is easier to erect and generally safer. Otherwise, you can construct a wood tower to hoist materials to the working height, like the one shown in Figure 7-9. Locate the tower where you can bring materials to it over the shortest haul, but far enough away from the structure to clear any external scaffolding. A clearance of 6 feet 8 inches is enough for scaffold platforms 5 feet wide. Construct the tower footing using two 2 by 12s, 2 feet long, placed under each 4 by 4 post. The height of the tower should extend at least 15 feet above the highest point where you need a landing. Then construct landings extending from the tower to the floors and scaffold platforms as needed. Use 2 by 10s or 2 by 12s for the landings.
Figure 7-9. Materials tower and elevator
7-30. Figure 7-9 also shows the elevator, rope, and pulley arrangement that serves the materials tower. Note the guides at the base of the elevator that fit onto the guides running up from the base of the tower.
|David L. Heiserman, Editor||
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Revised: June 06, 2015