Hazard Related Topics
Falls of persons from height represent the most serious safety risk in the construction industry. Many of these falls are from unsafe working places, or from unsafe means of access to working places. Scaffolds can be defined as temporary structures supporting one or more platforms and which are used either as a workplace or for the storage of materials in the course of any type of construction work. Whenever work cannot be done from the ground, or from the structure being worked upon, there should always be suitable and sufficient scaffolding. This should be properly constructed of sound material which is of adequate strength to provide a safe place of work and safe access to that place of work. Every scaffold and every working platform, gangway, ladder or any other equipment forming part of a scaffold, shall be used in such a way as to prevent persons from falling from the scaffold, or from being exposed to falling objects. Every scaffold must be inspected before being taken into use for the first time and at intervals of not more than seven days thereafter. It must be re-inspected after any major alteration or addition and after any exposure to any occurrence which may have affected its strength or stability.
General Access Scaffolds
- Must be designed, erected, altered and dismantled, by competent workers who are directed by a competent supervisor.
- Must be based on a firm, level foundation which should be capable of supporting the weight of the scaffold and any loads placed upon it. Care should be taken to avoid erecting the scaffold over voids such as drains, basements or on patches of soft ground.
- The uprights should have base plates resting on timber sole boards to spread the load and prevent the upright from sinking into the ground. They should be vertical or slightly inclined towards the structure and should be fixed sufficiently close together to secure the stability of the scaffold.
- The scaffold should be braced and tied into a permanent structure or otherwise stabilised. Ties should be put in place as the scaffold is erected and only removed as it is struck. Platforms should be fully boarded and wide enough to allow for safe access. They should not overhang their supports excessively e.g. no more than four times the thickness of the board.
- All scaffolds should be provided with secure guard rails and toe boards at every point where it is possible to fall two metres or more. Both should be fitted on the inside of uprights and guard rails should be between 950 mm and 1050 mm above the platform and toe boards should be at least 150 mm above the work platform to prevent materials being knocked over the edge of the platform. Intermediate rails must be provided so that the maximum vertical gap is 470 mm. If materials are stored on the platform to a greater height than this it may be necessary to provide wire mesh in fills between the toe board and guard rail.
These are used most frequently for work on tall buildings, or on structures above busy streets where it is not feasible to use a scaffold built from the ground. They are of two main types, suspended platforms and cradles. All are suspended from the building by means such as outriggers, tracks and parapet hooks. Typically accidents occur because of difficulty getting in or out of the cradle, insufficient or poorly secured counterweights, failure of suspension ropes and / or poor maintenance.
Access to the Scaffold
Normal access should be at roof, or ground level. If at roof level the guard rail of the platform or cradle should be at parapet level and only one person at a time should enter or leave.
A fall arrest device on a secondary rope should be used to safeguard against rope failure. All ropes should be examined by a competent person at least every six months.
The working platform or cradle should be inspected before each use and at least once each week. The safe working load should be clearly marked on the platform or cradle. In the case of a top guard rail it should be not less than 700 mm above the working platform.
The only people who should work from a suspended scaffold are those who have been trained in the use of the scaffold and its safety devices and who are aware of its safe working load and emergency procedures. All such workers must wear a safety harness with a lifeline securely attached to the building.
Every scaffold which is designed to be moved on skids or wheels must be constructed so that it is stable and it must be used only on a firm and even surface to prevent the risk of instability of the scaffold, or of any load upon it. Such scaffolds must be adequately secured to prevent movement when any person is working on it and be moveable only by the application of force at or near the base.
No chain, wire rope, lifting gear, metal tube or other means of suspension for slung scaffolds shall be used, unless the following requirements, where applicable, are met.
- It is suitable and of adequate strength for its purpose.
- It is properly fastened to safe anchorage points and to the scaffold ledgers or other main supporting members.
- It is placed so as to ensure the stability of the scaffold.
- It is as nearly vertical as is reasonably practical and it is kept taut.
Where chains or wire ropes are used as the suspension medium they shall be prevented from coming into contact at points of suspension with the edges where this would cause danger. Slung scaffold shall be secured so as to prevent undue horizontal movement whilst it is being used as a working platform.
Cantilever and Jib Scaffolds
No such scaffold shall be used unless it is adequately supported, fixed and anchored, has outriggers of adequate length and strength and is, where necessary, sufficiently and properly braced or strutted to ensure stability and rigidity.
Loads on Scaffolds
A scaffold must not be overloaded and as far as possible the loads should be evenly distributed. When material is placed on a scaffold it should be deposited without causing any violent shock. Materials should only be stored on a scaffold when they are to be used in a reasonable time.
- BS EN 12811-1:2003, Temporary works equipment (BSI)
- TG20:05, Guide to Good Practice for Scaffolding with Tubes and Fittings (National Access & Scaffolding Confederation - NASC)
- SG4:00, The Use of Fall Arrest Equipment Whilst Erecting, Altering & Dismantling Scaffolding (National Access & Scaffolding Confederation - NASC)