mtecadmin | February 25, 2020
With this post, we will attempt to provide an overview of this essential element of many building projects – scaffolding. A scaffold is a temporary structure, usually made of metal poles and wooden boards. Construction workers use scaffolding for access, and to support whatever is being built. Demolition and maintenance work above ground level need scaffolding. It is also used for shoring and formwork. Shoring is supporting, securing or propping up of another building. Formwork is the process of creating a mould for concrete or similar building materials. Scaffolding supports the mould until the concrete has set.
Internal Shoring
In addition to its uses in the world of construction, scaffolding also has a place as concert staging, lighting rigs, seating, art installations and exhibition stands.
Scaffolding stage at the Roundhouse in Camden, London.
The five principle types of scaffolding used today are tube-and-fitting, prefabricated modular system scaffolding, H-frame scaffolding, timber scaffolding and bamboo scaffolding. The latter two are not seen in the UK but are common in parts of China, India and Thailand.
Scaffolding consists of several components, which we will outline here. At ground level are the load-bearing base plates and sole boards. The vertical uprights are standards. Ledgers run across and pass weight through the standards. The transoms sit across the ledgers supporting the boards or decking. The working platform itself is usually steel banded, pressure-treated softwood boards. Steel and composite boards can also be decking components. The edges of the platform are always protected by a double handrail and toe boards.
Braces prevent sway or movement. There are three main types; ledger, sway and plan. Every second set of standards will have ledger to ledger bracing. Sway or facade bracing is every 5 bays or 10 meters across the front. The brace’s fix position must be no more than 300mm from the node point where standard meets ledger. Aberdeen tubes provide extra strength between internal and external standards at ledger brace positions.
Fittings or couplers join these components together. These primarily consist of right-angle couplers, single couplers, swivel couplers, sleeve joint pins, roofing couplers, beam clamps and board clips. Lubricating fittings keeps them rust free and easy to use. In a system scaffold, couplers are often pre-fabricated onto the individual components.
Hydra jaws in use testing the working load of ties holding scaffolding securely to a building.
A tie secures the scaffold to the structure and there are three main types. A physical tie goes inside the building or around a solid object. An operative drills a mechanical tie into a wall. The third tie is a chemical tie such as a resin anchor. Once struck, there is usually some ‘making good’ to do to remove these ties. A device called a hydra jaws tests the working loads of ties and ensures they meet legislative standards, measured as kilonewtons. Light duty ties can take a load of 3.5kN, standard duty 6.1kN load and heavy-duty ties up to 12.1kN. Ties come in many forms to allow fixings into different materials. A tie that is suitable for concrete may not be adequate for use on brickwork.
Beams span distances and can be steel or aluminium. They come in a variety of depths and lengths, depending on the strength required and the distances spanned. A qualified scaffolding engineer must design beam bridges and all temporary roof structures.
Aluminium beams spanning a large scaffolding temporary roof.
Beams are an integral part of a temporary roof. A temporary roof protects property and the workforce during inclement weather. The advantage of a ‘tin-hat’ is being able to continue work when other sites rain off. Scaffolding can cover significant areas using a variety of system or beam constructions. The roof itself is usually corrugated iron sheeting or coverings made of plastic. A temporary roof is a complicated structure and requires an advanced scaffolding qualification of those erecting it.
Debris netting to prevent debris and dust falling from scaffolding on a job in South West London.
Sheeting such as Monarflex stops dust and debris falling. It also provides excellent weather protection. Sheeting increases the wind load on the scaffold. Therefore, extra ties and support are necessary. The process of manufacturing debris netting and sheeting involves polypropylene plastic, which is not recyclable.
Moving workers and materials safely onsite with a system or Haki stair.
A ladder or purpose-built stair provides access to scaffolding. Ladders can be wooden, steel or aluminium. A painted ladder can hide deficiencies and is something to be aware of. To use a ladder safely maintain three points of contact such as two feet and one hand. As a result, taking tools and materials up a scaffolding structure is safer on a temporary staircase. A staircase can be system, modular scaffolding or made from tube and fitting components.
To lift and clear materials there are many options. A rope and wheel for lifting and lowering scaffolding components, as well as building materials and tools, is effective. Rubbish chutes are a simple solution for removing excess materials. A mechanical goods or passenger hoist is often installed on large building sites but needs extra ties and support.
A trades qualified scaffolder has an advanced ‘ticket’ and NVQ level 3. Scaffolders were previously classed as labourers which many felt was unjust. We will look at this in more detail in a future post.
A scaffolder has many tools in his arsenal. A swung over box spanner, spirit level and tape measure comprise the basic elements. Many scaffolders now use a cordless, rechargeable torque wrench spanner for speed and ease of use. However, some sites have banned these due to noise and the possibility of occasional sparks causing a fire or explosion.
Frogs connect tools to a tool belt. Tethers attach tools to the belt even when in use. This prevents them from falling onto anyone below.
We hope this overview has been helpful. Check back next week for the history and development of the industry. Future blog posts will cover training and trade bodies. We will look at the problems the industry faces with training up new scaffolders. We will cover health and safety legislation and proposed reforms. Then we’ll look at some of the projects MTEC has been proud to work on.