Scaffolding

“ Scaffolding used in Ceylon and other Eastern countries when erecting buildings is odd. The supports to which the floors of the scaffolding rest are bamboo poles, and the crosspieces and other material used to work on are held together by rope, no nails being used. The scaffolding is so bulky, crude and shaky that the walls of a building look as if they were out of plumb, but the scaffolding nearly always hides the new building entirely from view. ”

“ In scaffolding, the vertical timbers are known as standards or uprights. The horizontal timbers between the standards are known as ledgers when of cylindrical section, but as transoms and runners when of rectangular section. Braces, shores, struts and ties of any section are pieces used to stiffen the structure. The putlogs, or joists as they are called when of greater length, carry the boards which form the working platform. ”

“ Many accidents, again, occur owing to the scaffolding having been altered during a temporary absence of the mechanic, and the reconstruction not having been made safe by his return. This most frequently happens when the scaffolding is not under the charge of one responsible person. ”

“ In ordinary practice a scaffold is carried up with the walls and made to rest on them. Having built up as high as he can reach from the ground, the scaffolder erects a scaffold with standards, ledgers and putlogs to carry the scaffold boards (see Scaffold, Scaffolding) . Bricks are carried to the scaffold on a hod which holds twenty bricks, or they may be hoisted in baskets or boxes by means of a pulley and fall, or may be raised in larger numbers by a crane. The mortar is taken up in a hod or hoisted in pails and deposited on ledged boards about 3 ft. ”

“ In such places where the scaffolding has not been erected by the direct employer of the men using it, or where its management has not been under his personal or deputed control or supervision, he should satisfy himself either personally or by his agents before allowing his employees to work thereon that the foregoing suggestions are kept in force on that portion of the scaffold and building with which he is concerned. ”

“ It is therefore apparent that scaffolding timber, exposed as it is to the vicissitudes of the weather, without any protection such as would be gained by painting, will soon from this cause show signs of decay. ”

“ There is some objection to this method of scaffolding where the wall is more than 1 foot 101⁄2 inches thick (which is the greatest depth of brickwork over which a man can reach and do finished work) , for the mechanics, in order to reach the outside joints, have to kneel on the freshly laid material, which is detrimental to good workmanship. For this reason the system of carrying up an ordinary pole scaffold externally until the height is reached where the wall is reduced to 1 foot 101⁄2 inches in thickness, is to be preferred. ”

“ Third and fourth class masonry at prices for laying dry, to which will be added fifty cents per yard if laid in lime mortar, and one dollar if laid in cement.
SCAFFOLDING. 80. Nothing shall be allowed for workmanship or timber of any scaffolding used in the construction of timber bridges, or in carrying up abutments, piers, coffer-dams, or otherwise. Should the timber used in any coffer-dam be carried away by floods, the renewal of it shall fall upon the first party. ”

“ It is very easy for a single observer to lose a clear view of the whole, through using too complicated a scaffolding. Others follow; they test the solidity of the structure, they move the misplaced bricks into their correct position, and give a finishing touch to the parts that are insufficiently trimmed. ”

“ In all such cases science erects a scaffolding which is invariably kicked down as soon as its work has been accomplished. And, if the scientific architects are so captivated with the scaffolding that they insist upon maintaining it intact, its eventual demolition is none the less sure in the progress of observation and experiment. ”

“ Each new workman brings new tools, new ideas, and his own extensive experience with him, and tackles the whole structure from different points of view. Then the scaffolding is removed, and a mighty building appears, which scarcely gives any idea how diverse were the plans on which it was founded. So, too, this contribution to our knowledge of the functions of the cells may be considered only as an attempt to adjust a new stone in the already existing structure, and to construct a scaffold from which further progress may be made. ”

“ Petersburg poles are the most generally used for scaffolding. They are weaker than the Christiania poles, breaking shorter under cross strains, are whiter in colour, have a smoother bark, are straighter in grain, and therefore make better ladder sides. ”

“ Now there are two difficult operations which must at this time be put into course of execution—the one is the erection of scaffoldings for enabling the builders to work in safety, and which must be prepared both for the inside and outside of the fabric, where they will be required to sustain the weight of the men, the stones and the mortar, with space also for the crane to draw up the different materials, and for other machines and tools of various kinds. ”

“ Tied at their crossing-point, connections are made to all the main timbers of the scaffold with which they come in contact. Braces are fixed in all exposed situations, and generally where the scaffold is more than one pole (30 feet) in height.
Fig. 23
The only exception to effective bracing being carried out is where the building, being of irregular form, creates many breaks and returns in the scaffolding. It is obvious27 that where a scaffold butts against or breaks with a return wall, the tendency to lateral motion is lessened. ”

“ In some ancient time workmen made their way up, by scaffolding, three hundred feet and more above the road, where they smoothed a large space of the face of the rock, cutting out weak and soft portions, and carefully plugging the cavities with firmer and stronger pieces of the same stone. ”

“ With the smaller spans, the roof-trusses form very convenient supports for painters’ scaffolding or planking, but with the very large spans the greater height and the form of the roof-principals render specially designed scaffolding and appliances necessary for the painting and repairs. ”

“ The putlog holes show that round instead of square poles were used in the construction; and here, as at Coucy and in parts of Harlech, they are so placed as to show that the scaffolding was laid as an inclined plane, instead of horizontally, and with ladders. ”

“ All poles before being used in the construction of the scaffold should be barked.
This is generally done, but is imperative when the poles are to be used as standards. If not ripped off the bark acts as a sheath to the pole, and having little adhesion thereto will slip under pressure such as is exerted by the ledgers.
11. No work should take place on a working platform until its construction is complete, unless the portion incomplete is effectively guarded from the men using it.
In the course of building, the working platforms have to be raised as the work progresses. ”

“ A scaffold is usually within a few inches of the building, except where breaks in the wall of the erection occur, so that rails and edge boards are not usually necessary on the inside of the platform.
In allowing a reasonable distance on each side of a ladder, consideration must be given not only for the landing of workmen but also for material being carried ”

“ Nevertheless, the rule that the scaffold will not be in equilibrium unless a line from the centre of gravity fall within the base still holds good. In the case under consideration, as the wall of the building to which the scaffold is securely attached by the putlogs and ties, carries its share of the weight of the loads and putlogs, it must be taken as forming an integral portion of the scaffold itself. ”

“ Where this is the case, the lack of rigidity greatly increases the danger of collapse, as the timbers, through yielding by flexure to the loads that act upon them, allow such an alteration of the shape of the scaffold that the centre of gravity may be carried outside the base. ”

“ All bridging runs between different portions of a scaffold or building, and from which a workman could fall a distance of more than 8 feet, should be not less than 18 inches wide. If composed of two or more boards they should be fastened together in such a manner as to prevent unequal sagging. ”

“ Where increased strength is required a small rope can be attached to a larger one by means of a rolling hitch. The whole arrangement comes apart as soon as the strain is removed.
No. 41. A method of lifting scaffold poles in a vertical position by the use of the timber hitch and half hitch. If it is required to free the upper end while the pole is being carried, the half hitch can be replaced by a cord tied round the pole and the lifting rope.
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CHAPTER VI
SCAFFOLDING ACCESSORIES AND THEIR USE Ladders.—A ladder consists of a pair of sides connected by a series of oak or ash treads or rungs. ”

“ The boards are usually from 7 in. to 9 in. wide and 11⁄2 in. to 2 in. thick. Their length averages up to 14 feet. The ends are sawn as fig. 62 and strapped with iron to prevent splitting. When decayed they are a source of danger for which there is only one remedy—smash them up.
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CHAPTER V
CORDAGE AND KNOTS The fibres used for the ropes and cords for scaffolding purposes are of jute and hemp. ”

“ A light repairing scaffold lately put on the market has a platform which is supported and not suspended, but otherwise affords about the same scope to the workmen as the painters’ boats. It consists of one pole and a platform, the latter being levered up and down the pole as required by a man standing on the platform itself. The whole apparatus can be moved by one man standing at the bottom. ”

“ Lime mortar is used, cement being too rigid to allow the chimney to rock in the wind. Not more than 3 ft. in height should be erected in one day, the work of necessity being done in small portions to allow the mortar to set before it is required to sustain much weight. The bond usually adopted is one course of headers to four of stretchers. Scaffolding is sometimes erected outside for a height of 25 or 30 ft., to facilitate better pointing, especially where the chimney is in a prominent position. The brickwork at the top must, according to the London Building Act, be 9 in. ”

“ No scaffold is to project beyond the foot-way pavement where it is narrow, nor more than 6 feet where it is wide enough to admit of such projection; any deviation on account of special reasons is to be stated upon the license. ”

“ A guard-rail may at times interfere with the free use of the platform, and where this occurs an alternative is to fit the well hole with trap doors which can be closed when the well is out of use.
8. No loose putlogs or other timbers should be allowed to remain projecting from the face of the scaffold where hoisting or lowering of material or plant is carried on.
The danger from any projecting timbers is a real one. If loose the transport of material may disturb it by contact, or the material itself may fall. ”

“ This makes it practically impossible for the scaffold to fail by breaking away from the building under the influence of the loads it may carry. Shoring or tying is therefore not so important. Wind pressures have, however, a greater effect, especially when the direction is not at right angles to one of the faces of the scaffold. If in that direction, the tied putlogs would offer resistance. Braces are therefore imperative, and they should be fixed at right angles to each other, each pair thus bracing a portion of the height of the scaffold equal to its width. ”

“ Pole Scaffolds
Bricklayers’ Scaffolds.—A bricklayer’s scaffold consists of a series of upright poles or standards, to which are lashed horizontal poles, termed ledgers. The ledgers and the wall of the building carry the putlogs, on which boards are laid to support the workman, his material, and tools (fig. 13) .
The standards are first erected, and may stand singly or in pairs. In a repairing job, unless of great height, and where there is no great weight of material, single poles are sufficient. ”

“ THE STRENGTH OF A SCAFFOLD The strength of a scaffold equals the resistance that its members and their connections can offer to the strains that act upon it. The timbers used may fail in various ways. ”

“ The practice of allowing workmen to erect scaffolds without the aid of expert supervision, as is generallyvi the case, is to be strongly deprecated. The architect, builder, or clerk of works, should in all cases be responsible for their erection—the risk of defective or unsafe work being thereby minimised, and an economy often effected in both labour and material. ”

“ If of great height the standards may be unable to carry their own weight. For the cases where danger might be apprehended from this cause, fig. 37 shows a system of framing, which, being supported by the set-back in the thickness of the wall, will carry the upper standards. ”

“ The first are placed at right angles to the putlogs and project sufficiently to carry the boards which are laid parallel to the putlogs. To prevent the boards rising when weight is applied at one side of the scaffold, iron plates bolted together (fig. 33) are fixed at the corners, and clips (fig. 34) connect them to the putlogs.
Fig. 31
39
Fig. 32 Fig. 33
The stability of these scaffolds depends upon fixing at least two sets of putlogs, connected by means of stays as shown in fig. 32. Bracing is unnecessary if the putlogs and bolts tightly grip the building. ”

“ This instability may arise from various causes, the most common being the unequal settlement of materials in new buildings, the pulling down of adjoining buildings, structural alterations and defects, and alterations or disturbances of the adjacent ground which affect the foundations. ”