Scaffolding is a temporary structure used to support people and material in the construction or repair of buildings and other large structures. It is usually a modular system of metal pipes or tubes, although it can be from other materials.
This European Standard specifies performance requirements and methods of structural and general design for access and working scaffolds. Scaffolding Requirements given are for scaffold structures that rely on the adjacent structures for stability. In general these requirements also apply to other types of working scaffolds.
The purpose of a working scaffold is to provide a safe place of work with safe access suitable for the work being done. This document sets out performance requirements for working scaffolds. These are substantially independent of the materials of which the scaffold is made. The standard is intended to be used as the basis for enquiry and design.
Thus the requirements of BS EN 12811-1. TG20 is largely based on BS 5973 with extracts taken directly from the old code, it also uses permissible stress design method. However, TG20 received a mixed response from the UK industry and as a result TG20 is being re-written and the new version is due for release sometime in 2008. This is the reason for the 'limbo' situation. Until the release of the revised TG20 the HSE continue to allow scaffold to be built in accordance with BS 5973.
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. In Canada this style is referred to as "English". "American" has the transoms attached to the standards and is used less but has certain advantages in some situations. Since scaffolding is a physical structure, it is possible to go in and come out of scaffolding.
scaffolding can be errected in a manner of ways and is also know as the following:-