This section is from the book "Modern Buildings, Their Planning, Construction And Equipment Vol1", by G. A. T. Middleton. Also available from Amazon: Modern Buildings.
Scaffolds are of two general descriptions, namely - 1. Bricklayers' Scaffolds. 2. Masons' Scaffolds.
Standards are upright members - usually fir poles of an average diameter of about 5 inches, and varying from 10 to 30 feet in length. These standards are arranged in a row about 4 feet 6 inches from the face of the work, and at distances apart of about 8 to 12 feet. The lower ends of the standards are usually buried in the ground to a depth of about 2 feet, the flags being lifted to enable this to be done when the scaffold is to be erected over a flagged path, as shown at B, Fig. 232. When it is undesirable to disturb the pavement the standards are usually placed in tubs and filled round with earth and well rammed, as shown at C, the tubs being placed, if possible, at the centres of flags, so that the pressure of the standard will be well distributed. When the scaffold is high the standards are built up of two or more poles lashed together, the lashings being tightened by wooden wedges; and if the height exceeds the first set of poles, other lengths of pole are added as the work proceeds.
Ledgers, or Runners, are poles similar to those used for standards, and are fixed horizontally to the wall side of the standards by means of rope lashings tightened with wooden wedges. They are used to support one end of the putlogs, which in turn support the stages. It has been found that 5 feet is the greatest height at which a man can conveniently work, for which reason the ledgers are never spaced farther than 5 feet apart. Ledgers are lengthened by overlapping the ends and lashing them together and tightening by means of wedges, as shown in Fig. 232. The cords used for lashing are usually 8-feet lengths of hemp rope, three-quarter inches in diameter, bound at the ends to prevent fraying.
Putlogs are short lengths of birch split to a section of about 3 inches square, and cut to a length of from 5 to 6 feet. One end rests upon the wall while the other is supported by the ledger, to which it should be lashed for safety. These putlogs are spaced at intervals of from 4 to 5 feet. When the mortar of the brickwork round the ends of the putlogs has set, wedges are inserted round these ends to give greater security to the scaffold.
The Scaffold Boards, or Sheetings, are made from 8 to 12 feet long of 9 by 1 1/2 inches spruce, with the ends bound in iron to prevent them from splitting, and are laid close together upon the putlogs to form a stage for the bricklayers to stand upon. The ends of the scaffold boards are either overlapped upon one putlog, as shown at D, Fig. 232, or butted against one another over two putlogs fixed about 4 inches apart, as shown at E. Both these methods prevent the board from tipping up when walked upon, and thus prevents accidents. The stages are made much firmer by nailing battens across the under sides of the scaffold boards, thus preventing them from sagging independently.
Other boards are placed with one edge resting upon the stages, and nailed against the standards to prevent pieces of material from falling off. These are called Guard Boards.
Wooden rails, called Guard Rails, are also sometimes fixed against the standards, to minimise the chance of workmen falling from the stages.
Poles, called Braces, similar to those used for standards and ledgers, are placed diagonally across, and lashed and wedged to the outsides of the standards, as shown in Fig. 232, to stiffen the scaffold.
Scaffolds for Repairing Purposes are easily erected against existing walls in the following manner: A stout timber is laid at about 4 feet from the wall, and 1 1/2-inch fillets are raised to this, as shown at A, Fig. 232. The lower ends of the standards are placed in the troughs formed by these fillets, and the upper ends are rested against the wall, the lowest ledger being lashed to the standards. Headers are taken out from the walls just above the level of this ledger, and the ends of putlogs are wedged into the holes thus made. The standards are then pulled into vertical position by means of ropes, being prevented from falling by ropes taken through windows or from the roof tops, and the other ends of putlogs are lashed to the ledger. More putlogs are now inserted into holes cut into the wall, and lashed to the ledger to make it secure, and then the erection continues in the usual manner.
2. The Masons' Scaffold is built in a similar manner to the bricklayers' scaffold, but on account of the larger loads it usually has to carry it is made very much stronger, the standards being also closer together, while the whole is more heavily braced. As it is impossible to make holes in stone walls the putlogs have to be carried upon a second row of ledgers and standards, placed as near as possible to the wall without coming in the way of projecting cornices. The outer row of standards is placed about 4 feet away from the inner row. It is advisable, especially when the soil is soft, to rest the lower ends of the standards upon Sleepers or large Sole pieces to prevent them from sinking.
The putlogs are placed close spaced, and the stages are double boarded.
Sometimes scaffolds are erected on both sides of a wall. This is a good practice where a high class of work is required, but it is more economical to work the backs of walls from stages supported upon stout trestles carried on the floors. When scaffolds are erected on both sides of a wall they should be braced transversely through window openings.
Scaffolds are sometimes erected on the insides of walls only, but this is a bad practice, as it is difficult to finish the outsides neatly, or to properly inspect the work.