DEFINITIONS
Scaffold – A temporary structure consisting of standards, putlogs, ledgers, generally of bamboo, ballies, timber or metal to provide a working platforms for workmen and materials in the course of construction, maintenance, repairs and demolition, and also to support or allow hoisting and lowering of workmen, their tools and materials.
Standard or Upright – A vertical or near vertical member used in the construction of scaffold for transmitting the load to the foundation.
Ledger – A horizontal member which ties the standard at right angles and which may support putlogs and transoms.
Putlog/Boarer – A scaffold member spanning from ledger to ledger or from ledger/standard to a building and upon which the platform rests.
Transom – A member spanning across ledgers/standards to tie a scaffold transversely and which may also support a working platform.
Brace – A member fixed diagonally across two or more members in a scaffold to afford stability.
Bracing – Bracing is a system of braces or ties that prevent distortion of a scaffold.
Guard Rail – A horizontal rail secured to uprights and erected along the exposed edges of scaffolds to prevent workmen from falling.
Toe-Board – A barrier placed along the edge of the scaffold platform and secured there to guard against the falling of material and equipment.
Single Pole Scaffold – Single pole scaffold is a structure consisting of putlogs or bearers, the cutor ends of which are supported on standards or ledgers secured to a single row of standard and the inner ends resting on a wall. This is also known as a putlog scaffold
Double Pole Scaffold – Double pole scaffold shall mean a scaffold supported by two rows of standards connected together longitudinally by ledgers and transversally by transoms or bearers and suitably braced.
Outrigger (Cantilever) Scaffold – Outrigger scaffold shall mean a scaffold, the platform of which is supported by outriggers or thrust outs projecting from the building, the inner ends of which are secured inside the building.
Trestle – Trestle/Ghoda shall mean a self-supporting frame work of timber or metal on which a working platform is laid
Jhula (Boatswain’s Chair) – Jhula shall mean a seat to support a workman in a sitting position, supported by rope slings attached to a suspension rope
Raker -An inclined member fixed to a scaffold to ensure its stability.
Tie – A member used to tie a scaffold for a structure to prevent horizontal movement of the scaffold.
CONSTRUCTION
Parameter | Light Duty Scaffold | Heavy Duty Scaffold |
Purpose | For the use of carpenters, painters or other similar trades and to support no other load except the workmen and a minimum quantity of working material/tools. | For the use of stone masons, concreting or other similar trades, and to support, in addition to the workmen, a nominal supply of building material. |
Safe Working Load | 150 kg/m2 | 300 kg/m2 |
Number of Platforms | Work shall not be carried on more than one platform at any time. | May have two working platform bays at any one time. |
| Parameter | Single Pole Scaffold | Double Pole Scaffold |
| Suitable distance of upright pole from wall | 1.8m | The inner row next to the wall and outer row at a distance of 1.2 to 1.5 m away from the wall. |
| Distance between ledgers | 1.5m to 1.8m | 1.5m to 1.8m |
| Putlogs spacing | 1.2m | Entirely rest on the scaffold ledgers. |
| Bracing | Longitudinal Bracing on outer face. | Both longitudinal and Transverse. |
| Distance between braced bays | Maximum shall not exceed 10m. | Maximum shall not exceed 10m. |
| Length of brace | Continuous except in change of direction. | If the length of the scaffold exceeds 15 m, it shall be provided in addition at intervals not exceeding 15m. |
| Mean diameter d | Not be less than 80mm subject to a minimum of 50 mm at the top | Not be less than 100 mm, subject to a minimum of 50 mm at the top. |
| l/d ratio | should not exceed 50 | should not exceed 50 |
| d is average of the diameters at the top and the bottom. l is the length of the standard between putlogs. | ||
Outrigger Scaffold:
1. It consists essentially of a platform placed on horizontal thrust outs extending through window. Or other wall opening and anchored on the inside of the building.
2. Outrigger scaffolds providing only one working platform shall be constructed of 75 mm x 150 mm timber outriggers projecting edgewise not more than 1200 mm through the wall or opening.
3. They should not be spaced more than 2m, apart and should be fastened securely
Tying
Height of Scaffold | Horizontal Spacing of ties | Vertical Spacing | ||
| GL-6m | 6m-8m | 12m-18m | ||
| Up to 6m | Every fifth standard or 10m. | – | – | 4m |
| Up to 12m | Every fourth standard or 8m. | Every fifth standard or 10m. | – | 4m |
| Up to 18m | Every third standard or 6m. | Every fourth standard or 8m. | Every fifth standard or 10m. | 4m |
RAILINGS AND TOE BOARDS
1. Should be provided for all working platforms higher than 2m above the floor level.
2. The railings shall consist of a top rail from 900 to 1050 mm above the platform level and intermediate rail halfway between the top rail and the platform. Standard railings may be constructed, of wood, pipe or any other metal sections.
3. Toe board shall be so. placed that no opening remains between the flooring and the toe board.
MEANS OF ACCESS
Ladder: Portable ladders are not recommended for heights above 4m. They should be placed at an angle of approximately 750 from the horizontal. Both top and bottom should be secured to prevent displacement, and the ladder rails should be extended at least 1 m above the top landing. Fixed ladders should be provided for flights above 4 m. Fixed ladder should have landings of minimum 600 mm extent at intervals not greater than 6.0 m. The width of ladder shall not be less than 300 mm and the rungs shall be spaced not more than 300 mm.
Ramps or Gangways: Where used, they should be built to provide strength equal to that specified for scaffold structures and should not unduly rag under the corresponding dead or moving loads. If the ramp or runway is 1.5 m or more above the ground or floor level, by standard railings and toe boards the open sides should be protected. The slope of the ramp shall not exceed 2 in 3. Where the slope is more than 1 in 4, proper foot holds shall be provided by means of stepping laths of minimum size 50 X 30mm at intervals not exceeding 45 cm.
Stairways – For scaffolds exceeding 4 m height, stairways are the safest means of access. The stairway shall conform to the following requirements:
a) Treads and risers should be of uniform width and height in any one flight
b) Minimum width of 1.0 m,
c) No unbroken vertical rise of more than 4 m,
d) Maximum angle of ascent 50 degrees,
e) Stair railings on all open sides,
f) Hand rails on all enclosed sides, and
g) Standard railings and toe boards on all landings.
PROTECTION FROM FALLING BODIES
1. To protect workers on lower platform against falling objects from higher levels, overhead protection should be provided on the scaffold. This protection should be not more than 3 m above the platform/floor and should be planking or other suitable material.
2. Protection Under Scaffolds – Where persons are required to work or pass underneath (for example, building entrances or pathways,) a scaffold upon which men are working, a screen or canopy shall be provided for their protection from falling objects. Such screen should extend to a distance at least one meter beyond the edge of the scaffold above the passage to catch any material which may fall. For ordinary conditions a net with a mesh size of 25 mm.
PLATFORM WIDTH
Where platform is not more than 2 m above the ground or floor:
a) Painters, decorators or similar workmen- 300 mm
b) Other types (men and tool only)- 500 mm
Where platform is more than 2’0 m above the ground or floor:
a) Men, tools and material 900 mm
b) Men, tools, material and wheel barrows 12OO mm
PRECAUTIONS AGAINST PARTICULAR HAZARDS
Electrical Hazards: Care shall be taken to see that no uninsulated electric wire exists within 3 m of the working platform, gangways, runs, etc of the scaffold. While carrying bars, rods or pipes of any kind conducting material of 1ength greater than 3 m, in the vicinity of electric wires, special care shall be taken that these do not touch the electric wires.
Fire Hazards – Care shall be taken against any possibility of timber scaffolds catching fire.
Mechanical and Traffic Hazards:
1. Care shall be taken to see that no part of a scaffold is struck by a truck or ether heavy moving equipment and no material shall be dumped against it.
2. Scaffolds on thorough fares shall be provided with warning lights, if general lighting is not sufficient to make it clearly visible.
3. Access to fire alarms, cable tunnels, hydrants, etc, shall remain free at all times. Care should be taken for underground cables and equipment when parts of scaffolds or other fasteners have to be driven in the ground.
4. Scaffolds or other rigging involving- human safety, should be tested with a load at least three times that which it will carry in service.
Source : IS 3696:1987 Part-1
