What is Scaffolding ?
Scaffolding is a temporary rigid structure having platforms raised up as the building increases in height. Scaffolding enables the mason to work at different stages of a building and to hoist the materials for the immediate use at various heights.
Types of Scaffolding Used in Building Construction.
The following different types of scaffolding are in common use:-
1. Brick Layers Scaffolding:
It consists of vertical members called standards firmly secured in grounds at 2.4 to 3 m. The standards are connected to each other by longitudinal horizontal members called ledgers at every rise of 120 to 150 cm. They are provided on the building side of the standards and are secured in position by rope lashings. Transverse horizontal members called put logs are lashed on the ledgers at one end and into the holes in the wall at the other end. Put logs are 90 cm. in length and are generally spaced 120 cm. a part. They are provided to support the working platform. In high scaffolding, cross braces are invariably used to stiffen the temporary structure. Braces consist of poles tied by rope lashing on the standards.
Mason’s Scaffolding: It is difficult to leave holes in the Stone Masonry to provide bearing for the put logs, in mason’s scaffold two frames of standards, ledgers and braces are used. One is placed close to the wall and the other at a distance of 1.5 m. from the first one. Thus the mason’s scaffold is entirely independent of the stone wall.
2. Close Mason’s Scaffolding
They are supported to carry the loads of heavy blocks of stones and the stresses produced on account of the lifting device and hence they are made stronger by placing the standards at fairly close distance apart.
3. Steel Scaffolding
The construction of steel scaffolding is essentially similar to that of timber scaffold. In this case, the wooden members are replaced by 38 mm. to 64 mm. in diameter steel tubes and instead of rope lashings, special types of steel couplets or fittings are used for connecting different members. The steel tubes used for scaffolding for normal building construction work are of heavy class and of diameter varying from 40 to 60 mm. In this type of scaffolding the vertical tubes called uprights or standards are spaced 2.5 to 3 m. apart. Each standard is welded to a base plate, square or circular in plan. The base plate has holes so that it can be spiked to a timber or concrete base, thus forming rigid foundation for the scaffolding. Ledgers or the longitudinal tubes connecting the standard and are spaced at 1.8 m. vertically apart. Short tubes or put logs are normally 1.2 m. to 1.8 m. in length. The put logs have special ends to fit into the joints in the wall and thus no big holes are required to be left in the wall for their bearing.
Tubular scaffolding has several advantages over the timber scaffolding such as rapid erection and dismantling, greater strength and durability and higher fire resisting qualities and salvage value. Although it works out to be costlier initially, but considering its several advantages and the increased number of reuses, it proves to be economical in the long run and hence it is being extensively used these days. Tubular scaffolding, mounted on wheels can be used for carrying out the work of painting the walls, under side of roofs etc.
4. Needle Scaffolding
When scaffolding is to be provided for a building on the side of a busy street where the construction of ordinary scaffolding will obstruct the traffic on road, needle scaffolding is use. The scaffolding is erected from window corners or string courses by means of projecting needles. A needle is timber beam which cantilevers out through the holes cut in wall. From inside the needles are supported on sole pieces and are prevented from lifting up by vertical struts wedged between the needles and the head pieces. The projected end of needle is supported by an inclined strut which rests on the window still. The joint between the raking or inclined strut and the needle is clamped by means of dogs. The arrangement provides the staging for erection of ordinary type of scaffold.
Gantries: There are two different types of wooden gantries:
a) Gantry with Traveler or Crane: When the stone blacks used in the wall construction are too heavy, crane traveler have to be used. The framework of gantry consists of timber standards raised on either side of wall. Longitudinal members called runners are fixed on the top of the standards, while at the bottom, the standards are fixed to common sole piece. Rails are fixed on the runners to carry the travelling platform. The travelling platform consists of trussed beams carrying lifting tackle, which can run on wheels on rails fixed on runners. This enables the travelling platform to move parallel to the wall along its length.
In addition, the beams of travelling platform have rails, so that the lifting tackle can move in a direction perpendicular to the wall. Thus the blocks of stones can be placed in any desired direction while building the wall.
b) Platform Gantry: This is needed for providing a working platform above ground level and leaving the space below free from obstruction. Platform gantry is adopted in stone masonry construction as it can be used independent of wall. The gantry consists of vertical posts fixed to common sole piece as its base and to a head piece at the top. The head pieces support the joists on which the working platform is laid. The entire framework is thoroughly braced and dogged. A 90 cm. high boarding is fixed on the outside of the gantry to prevent the material on the platform from falling down.