Scaffolding and Its Various Types
Definition of Scaffolding: For temporary structure the term scaffolding is used which provides support to the concrete formwork or to provide a support to the workmen during the construction (during brickwork, plastering, and painting or renewal or repainting of structures, etc.)
Scaffolding comes under safety regulations on construction sites, there is a standard which is mentioned for its usage and layout.
Such as in case a person is liable to fall from more than 2 meters height, a guardrail must be provided to a height of 1 meter along with a toe board at least of 200mm above the platform.
Around the periphery of the building scaffolding is built. In multistory buildings, it is important to assemble it to very large heights.
Faulty scaffolding leads to 35 to 40 percent of all accidents that takes place in building construction sites. Faulty scaffolding leads to persons’ fall from heights, therefore, it is important to maintain strict supervision while putting up the scaffolding according to the standard practices.
It is best to hire industry experts like Bristol scaffolding to minimize accidents on the construction site.
The various parts of scaffolding
Scaffolding consists of the following parts:
- Standards: The vertical posts (also called uprights).
- Ledgers: The horizontal members which are parallel to the wall.
- Braces: The bracing system.
- Putlogs: Horizontal members which are normal to the wall.
- Transoms: Putlogs, both ends of which is supported on ledgers in double scaffolding.
- Bridle: Member that are used to bridge openings.
- Boarding: Planks used by workmen to stand.
- Guard rail: The rail built at about 1 m level to guard the men who are working on the boarding.
- Toe board: Boards that are placed parallel to boarding near the wall to be able to provide protection to workers.
- Base plate or sole plate: Plates on the ground which provides support to the standards.
The common types of scaffolding are mentioned below:
1. Single scaffolding or bricklayers scaffolding
An outer vertical row that is present to which longitudinal members are tied at various levels of working; this type of scaffolding is commonly used for brickworks.
The putlogs or cross members are tied together with the standards at the outer end and rest of the wall is built inside. The platform is then carried on the putlogs. Between the verticals at the vertical planes cross bracing is introduced for lateral stability. In case the vertical posts cannot be placed on base plates or in holes made in the ground, it should be carefully placed and braced for lateral stability. The most widely used method is to place the vertical post in a steel barrel of 60cm in height and of suitable diameter which will be filled with compacted earth.
2. Double scaffolding or Mason’s scaffolding
This method is used by mason for supporting system in case of plastering. It has two pairs, inner and outer verticals. The putlogs which instead of being supported on the wall are instead supported on an inner system of verticals and longitudes.
3. Cantilever or needle scaffolding
Cantilever scaffolding is used for constructing the upper part of tall residential buildings, it helps in eliminating unwanted scaffolding at lower levels which helps in keeping free space for vehicles, etc.
4. Birdscage scaffolding
It is mostly used for internal work and it consists of a simple cage which is supported on four verticals from which workers can work. It is movable and can be moved easily from one place to another.
5. Ladder or trestle scaffolding
This is made to use for light work and it is therefore portable. It consists of two ladders whose top ends are joined together by planks so that a person can work on this platform.
6. Suspended scaffolding
For working at high levels in tall buildings, for example in painting of tall buildings, it is more convenient and economical to suspend the working platform from a height above the ground than to support from the ground. This takes place when the height is more than 30 meters.
Three types of suspended scaffolding are — fixed, operated by pulleys and those that are operated by winches.
i. Fixed type suspended scaffolds
These scaffolds are those which are attached to a truss or the roof truss which is above the site of work using ropes, chains, tubes, etc.
ii. Suspended scaffolds which are operated by pulleys
These are the platforms that are required by the window cleaners and painters of a building.
iii. Suspended scaffolds operated by winches
These are the heavy platforms which are hung from temporary outriggers and can be operated by external cranes.
Important Points in Scaffolding
During scaffolding work the following important rules must be remembered:
1. It is important to remember that the uprights (standards) must not be spaced more than 1.8 m (6 ft) in terms of heavy work such as masonry and should not be more than 3 m (10 ft) for light work for example painting.
2. On the wall opening the putlogs must bear well in single scaffolding. The short members that are nailed onto the wall must not be used as putlogs.
3. Wide enough platforms must be used. In case the height is more than 1.8 meters than it should not be less than 17 inches (425mm) in width.
It should not be more than 850mm or 34 inches in width if materials are stored in it.
In thickness each board must be 50mm (2 inches) and must be 200mm (8inches) wide for the spacing for putlog which are 1.5m or even more. In case of 0.9m to 1.5m it can be 38mm (11/2 inches) thick and for less than 1.5m in putlog spacing it must be 25mm (1 inch).
4. There should be no defect in the plank. To avoid any sudden failure of the planks, it must be noted that the grains in the wood used must not be any more than 10 degrees with the length of the plank.
The planks should not be overhung or cantilevering scaffolding must not be followed.
5. To check that the scaffolding must not fall from the wall laterally they should be properly strutted. The stability even in the longitude is required as well.
6. Under the scaffolding no work men should work.
7. No lorries should be allowed to come anywhere near the scaffolding.
8. There must be the availability of safe ladders to climb on to the scaffolding.
9. Guard rails must be provided for the scaffolding if the height is more than 2 meters.
Where to use Steel Tube Scaffolding
Commonly, for ordinary low-rise buildings, bamboo or casuarinas are tied together by the coir ropes for the scaffolding which makes the work a lot cheaper.
It must be remembered that the strength of these poles is lost once they are exposed to the sun for a period of six to nine months after which they must be replaced.
It is also important to check the strength and tightness of the coir rope joints periodically.
In case of buildings or structures with large heights, and for a longer period of usage, steel tube scaffolding or wooden systems which are specially made with special fixing devices are mostly preferred.
For multistory building it is best to use steel scaffolding which are strong and can be easily joined. Using steel scaffolding also leads to minimum accidental cases which is another reason why it should be used.