For heights not to exceed 20 feet, the uprights shall be of 4-inch by 4-inch lumber or heavier material, with a space of 4 feet between uprights at right angle to the wall and not more than 7 feet, center to center, parallel to the wall. (b) When buggies are used on scaffolds to transport concrete, a strong scaffold shall be designed that is capable of supporting a concentrated load equal to the weight of a loaded buggy at any point on girders, beams, or planking.
(a) Pole scaffolds to be used by bricklayers, stonemasons, concrete workers, or other trades using heavy tools or storing heavy material on the scaffold shall be constructed as follows:
