Using a ladder as a means of access is quicker and easier, but it is not always the safest. Jobs, such as painting, gutter repair, demolition work, or window replacement, are often easier using a scaffold. A scaffold need not be considered if the work can be completed comfortably using ladders. Scaffolds must be capable of supporting building workers, equipment, materials, tools, and any accumulated waste. A common cause of scaffold collapse is the ‘borrowing’ of boards and tubes from the scaffold, thus weakening it. Falls from scaffolds are often caused by badly constructed working platforms, inadequate guard rails, or climbing up the outside of a scaffold. Falls also occur during the assembly or dismantling process.
Basic Types Of External Scaffolds
There are two basic types of external scaffolds:
- Independent tied – These are scaffolding structures independent of the building but tied to it, often using a window or window recess. This is the most common form of scaffolding.
- Putlog – This form of scaffolding is usually used during building construction. A putlog is a scaffold tube that spans horizontally from the scaffold into the building – the end of the tube is flattened and is usually positioned between two brick courses.
Important Components Of A Scaffold
The important components of a scaffold have been defined in a guidance note issued by the HSE as follows:
- Standard – An upright tube or pole used as vertical support in a scaffold.
- Ledger – A tube is spanning horizontally and tying standards longitudinally.
- Transom – A tube spanning across ledgers to tie a scaffold transversely. It may also support a working platform.
- Bracing – Tubes span diagonally to strengthen and prevent movement of the scaffold.
- Guard rail – A horizontal tube fitted to standards along working platforms to prevent persons from falling; it should be at least 950 mm high and no more than 470 mm between the toe boards and the intermediate rail and top rail.
- Toe boards – These are fitted at the base of working platforms to prevent persons, materials, or tools from falling from the scaffold.
- Base plate – A square steel plate fitted to the bottom of a standard at ground level.
- Sole board – Normally, a timber plank is positioned beneath at least two base plates to provide a more uniform distribution of the scaffold load over the ground.
- Ties – Used to secure the scaffold by anchoring it to the building. The scaffold in Figure (a) is tied to the building using a through-tie.
Working platform – An important part of the scaffold is the platform on which the building workers operate and where building materials are stored prior to use. These are laid on the transoms in various quantities; usually, they should be four boards wide. A working platform can be almost any surface from which work can be undertaken, such as:
- a roof
- a floor
- a platform on a scaffold
- mobile elevating work platforms (MEWPs)
- the treads of a stepladder
Other scaffold components include access ladders, brick or block guards, and chutes to dispose of waste materials.
The following factors must be addressed if a scaffold is being considered for use for construction purposes:
- Scaffolding must only be erected by competent people who have attended recognized training courses.
- A competent person must supervise any work carried out on the scaffold. A competent person must make any changes to the scaffold.
- To prevent people or materials from falling, adequate toe boards, guard rails, and intermediate rails must be fitted. The top guard rail should be a minimum of 950 mm above the working platform, and any gap between the top rail and the intermediate rail should not exceed 470 mm. The toe-boards must be suitable and sufficient to prevent people or materials from falling.
- The scaffold must rest on a stable surface; uprights should have base and timber sole plates.
- The scaffold must have safe access and egress.
- Work platforms should be fully boarded with no tipping or tripping hazards.
- The scaffold should be sited away from or protected from traffic routes to avoid being damaged by vehicles.
- Lower level uprights should be prominently marked in red and white stripes.
- The scaffold should be properly braced and secured to the building or structure.
- Overloading of the scaffold must be avoided.
- The public must be protected at all stages of the work. Barriers/signage must be displayed, and measures to take if unattended.
- Regular inspections of the scaffold must be made and recorded.
Pre-fabricated Mobile Scaffold Towers
Mobile scaffold towers are frequently used throughout the industry. The workers must be trained in their use as recent research has revealed that 75% of lightweight mobile pre-fabricated tower scaffolding is erected, used, moved, or dismantled unsafely.
The following points must be considered when mobile scaffold towers are to be used:
- The selection, erection, and dismantling of mobile scaffold towers must be undertaken by competent and trained persons with maximum height-to-base ratios not being exceeded.
- Diagonal bracing and stabilizers should always be used.
- Access ladders must be fitted to the narrowest side of the tower or inside the tower, and persons should not climb up the tower’s frame.
- All wheels must be locked while work is in progress, and all persons must vacate the tower before it is moved.
- The tower working platform must be boarded, fitted with guard rails and toe boards, and not overloaded.
- Towers must be tied to a rigid structure if exposed to windy weather or used for work such as jet blasting.
- Persons working from a tower must not over-reach or use ladders from the work platform.
- During working operations and when the tower is moved, safe distances must be maintained between the tower and overhead power lines.
- The tower should be inspected regularly, and a report made.
Anyone erecting a tower scaffold should be competent and should have received training under an industry-recognized training scheme, such as the Prefabricated Access Suppliers and Manufacturers’ Association (PASMA) or under a recognized manufacturer or supplier scheme.