Scaffold

Scaffold in Geneva. Please find here after some explanation regarding scaffold:

Basic materials are tubes, couplers and boards.

Scaffold tubes are either steel or aluminium. If steel they are either 'black' or galvanised. The tubes come in a variety of lengths and a standard diameter of 48.3 mm. The chief difference between the two types of tubes for Scaffold is the lower weight of aluminium tubes (1.7 kg/m as opposed to 4.4 kg/m) and also a greater flexibility and so less resistance to force. Tubes are generally bought in 6.3 m lengths and can then be cut down to certain typical sizes.

Boards provide a working surface for users of the scaffold. They are seasoned wood and come in three thicknesses (38 mm (usual), 50 mm and 63 mm) are a standard width (225 mm) and are a maximum of 3.9 m long. The board ends are protected by metal plates called hoop irons or sometimes nail plates. As well as timber, steel or aluminium decking is used or laminate boards. As well as boards for the working platform there are sole boards which are placed beneath the scaffolding if the surface is soft or otherwise suspect, although ordinary boards can be used, and meet the minimum requirements, they can be too long and tougher boards can be necessary.

Couplers are the fittings which hold the tubes together. The most common are called scaffold couplers, there are three basic types: right-angle couplers, putlog couplers and swivel couplers. To join tubes end-to-end joint pins (also called spigots) or sleeve couplers are used, or both together. Only right angle couplers and swivel couplers can be used to fix tube in a 'load bearing connection'. Single couplers are not load bearing couplers and have no design capacity.

Other common materials lnclude base plates, ladders, ropes, anchor ties, reveal ties, gin wheels, sheeting etc.

Basic scaffolding
The key elements of a scaffold are standards, ledgers and transoms. The standards, also called uprights, are the vertical tubes that transfer the entire mass of the structure to the ground where they rest on a square base plate to spread the load. The base plate has a shank in its centre to hold the tube and is sometimes pinned to a sole board. Ledgers are horizontal tubes which connect between the standards. Transoms rest upon the ledgers at right angles. Main transoms are placed next to the standards, they hold the standards in place and provide support for boards; intermediate transoms are those placed between the main transoms to provide extra support for boards.

As well as the tubes at right angles there are cross braces to increase rigidity, these are placed diagonally from ledger to ledger, next to the standards to which they are fitted. If the braces are fitted to the ledgers they are called ledger braces. To limit sway a facade brace is fitted to the face of the scaffold every 30 metres or so at an angle of 35°-55° running right from the base to the top of the scaffold and fixed at every level.

Of the couplers previously mentioned, right-angle couplers join ledgers or transoms to standards, putlog or single couplers join board bearing transoms to ledgers - Non-board bearing transoms should be fixed using a right-angle coupler. Swivel couplers are to connect tubes at any other angle. The actual joints are staggered to avoid occurring at the same level in neighbouring standards.

The spacing of the basic elements in the scaffold are fairly standard. For a general purpose scaffold the maximum bay length is 2.1 m, for heavier work the bay size is reduced to 2 or even 1.8 m while for inspection a bay width of up to 2.7 m is allowed.

The scaffolding width is determined by the width of the boards, the minimum width allowed is 600 mm but a more typical four-board scaffold would be 870 mm wide from standard to standard. More heavy duty scaffolding can require 5, 6 or even up to 8 boards width. Often an inside board is added to reduce the gap between the inner standard and the structure.

The lift height, the spacing between ledgers, is 2 m, although the base lift can be up to 2.7 m. The diagram above also shows a kicker lift, which is just 150 mm or so above the ground.
Transom spacing is determined by the thickness of the boards supported, 38 mm boards require a transom spacing of no more than 1.2 m while a 50 mm board can stand a transom spacing of 2.6 m and 63 mm boards can have a maximum span of 3.25 m. The minimum overhang for all boards is 50 mm and the maximum overhang is no more than 4x the thickness of the board.

Foundations
Good foundations are essential. Often scaffold frameworks will require more than simple base plates to safely carry and spread the load. Scaffolding can be used without base plates on concrete or similar hard surfaces, although base plates are always recommended. For surfaces like pavements or tarmac base plates are necessary. For softer or more doubtful surfaces sole boards must be used, beneath a single standard a sole board should be at least 1,000 cm² with no dimension less than 220 mm, the thickness must be at least 35mm. For heavier duty scaffold much more substantial baulks set in concrete can be required. On uneven ground steps must be cut for the base plates, a minimum step size of around 450 mm is recommended.

A working platform requires certain other elements to be safe. They must be close-boarded, have double guard rails and toe and stop boards. Safe and secure access must also be provided.

Scaffold

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Scaffold