SCAFFOLDING SCAFFOLDING Scaffold is a term used to

SCAFFOLDING

SCAFFOLDING "Scaffold" is a term used to describe a temporary structure for the support of workers and their materials during building operations. u There a number of different types of scaffolds but for GRADE 11 CIVIL TECH, only the following three types will be discussed: u – steel trestles and frames; – independent scaffolds; – mobile scaffolds.

Steel trestles and frames Trestle scaffolds must be strong enough to carry the loads imposed on them. u You should not use them if you need a height higher than 4, 5 m. u You must be especially careful never to erect a trestle scaffold on top of another trestle scaffold or on top of any other scaffold type platform for that matter. u Trestle scaffolds are normally only used for light work of short duration. u

Steel trestles and frames You should also not erect them for the sole purpose of storing materials on them. u Trestles are usually of the folding type and do not normally require guard rails and toe boards. u You should be very careful not to load them too heavily because they are not as stable as the normal conven tional scaffold. u There are various kinds of trestles for specific types of light work, and these are shown in the figures below. u

Double folding trestle u This is an independent 4 board working platform trestle which can be used for every type of interior or exterior work. u It can be easily handled by one man and folds compactly for storage and transport. u Height 1 067 mm 1 829 mm u Weight 26, 8 kg

Double folding trestle

Ceiling trestle This kind of trestle is designed for low level access in places where a ladder or another means of support is not suitable. u It will give access to standard storey height ceilings and it has 3 platform height adjustments. u All the tubular steel construction of this kind of trestle is completely self contained, and it has no loose fittings. u Height. 1 219 mm 2058 mm u Weight 28, 6 kg u

Ceiling trestle

Putlog Trestle u This kind if trestle is ideal for bricklayers and those who work in the finishing trades. u It can also be used on uneven ground. u It folds compactly for storage and transport. u Height. 1 372 mm 2 439 mm u Weight 30 kg

Putlog Trestle

Framed scaffolds This kind of scaffolding is ideal for erecting towers, scaffolding, bricklaying, etc. , u It is manufactured from high tensile steel. u Such scaffolds provide a rigid, safe working platform that can be quickly erected by a minimum number of workers who have no special skills. u

Framed scaffolds u They can also therefore be easily dismantled and packed away. u They can withstand loads well in excess of normal loading. u No tools are required because the system simply slots together. u To erect them, we simply follow the following procedure:

Framed scaffolds Fit two frames together by using base plates or base jacks. u Position the two frames and then brace them with cross braces and a plan brace. u Now slot the next two frames at right angles to the first pair. u Insert plan braces at every 6. 5 m interval. u Lay scaffolding planks across the top to form a work platform. u Insert guard rails (tie bars). u

Framed scaffolds

Cross-braces u These are made from high tensile steel and are joined at the centre by a rivet. u All braces are stamped with their size and they can fit either 12 mm or 16 mm gravity locks.

Cross-braces

Gravity Lock

Flat Head

Base or Head Jack

Multi-frames These are also ideal for towers, scaf folds, etc. u They are made of high tensile steel and are erected the same way, viz. by using cross braces with gravity locks. u They can carry up to 26 k. N per leg. Multi frames are fitted with three pairs of gravity locks. u This makes them exceptionally stable. u

Multi-frames

Independent scaffolds u This type of scaffold (as the name implies) stands on its own. u It has two rows of standards which are connected by transoms. u Although it is independent, it nevertheless requires the additional security of being tied to the building at window openings, for example.

Independent scaffolds A horizontal tube called "a bridle bearing" may be used on the inside of the wall and across a window opening, with cross members connected to it. u Another fixing method is to use a reveal pin in the window opening. u If there are no openings, the scaffold should be strutted from the ground using raking tubes which are inclined towards the building. u

Independent scaffolds

Scaffold boards: u u u These are pine boards whose quality has been approved by the SABS. They are 225 mm x 38 mm and should not exceed 4, 8 m in length. If these boards are left just as they are, the ends will be inclined to split. To prevent this, you should bind the ends with strips of galvanised hoop iron. The boards should be strong enough to support a load of approximately 6, 5 k. N/m 2 if it is supported at 1, 2 m intervals.

Fittings: u These are manufactured of steel or an aluminium alloy and are approved by the SABS. Some of the most commonly used fittings are: – Double coupler – Swivel coupler

Double coupler u This is used to join ledgers to standards. u They are load bearing.

Double coupler

Swivel coupler u This consists of two single couplers attached to each other in such a way that they can rotate and be used to connect two tubes at any angle.

Putlog end u This consists of a flat plate that is fitted to the end of a tube so that it can be pushed into the perpendicular joint of brickwork to support the boards.

Base plate u u u This is a square plate with a spigot. It is inserted to the bottom end of a standard for load distribution on top of a sole plate. They are also found with threaded spigots for use on sloping ground.

Split joint pin (Figure 3. 45). This is a fitting used to connect or join two tubes end to end. u It has a centre bolt which expands the pin so that it can grip inside the tube. u

Mobile scaffolding u When a mobile scaffold is required, castor wheels replace base plates. u On irregular surfaces, adjustable jacking castors are used. u Mobile scaffolds should not be more than three times higher than their narrowest width at the base unless additional support such as outriggers, at the base, are used.

Mobile scaffolding Castor wheels should be fixed in such a way so as to prevent accidental displacement. The same principles are applied as for normal independent scaffolds. u Mobile scaffolds must only be moved from the bottom end and never be moved or adjusted while workers are on them. u

Mobile scaffolding u Right angled couplers must be used for fixing uprights if the scaffold is to be erected out of tubes. u Under no circumstances should cantilevers be used on mobile scaffolds or any loads imposed outside the line of the verticals or standards.

Safety precautions for scaffolding All materials used must be in good condition and without any defects. u Scaffolds must be inspected by a competent person after erection, before being used, and after rainy weather. u They must also be inspected at least once every week. u Where timber is used it should not contain any bark or be painted so that defects are hidden. u

Safety precautions for scaffolding u u The ground on which the scaffold will stand must be leveled and compacted to make it firm enough to carry any load. Sole plates and base plates must be used. Scaffold boards are ideal sole plates. . Standards should not be placed more than 2 m apart and each one should be slightly inclined towards the building. Ledgers must be fixed to standards by load bearing couplers and they must be level. The vertical distance between ledgers must not exceed 2 m. Transoms or putlogs should be fixed at a maximum span of 1, 5 m. Boards must not overhang their supports by more than four times the thickness of the boards.

Safety precautions for scaffolding Guard rails and toe boards must be fixed to working platforms if such platforms are higher then 2 m. u All scaffolds must be properly braced and tied to a building that is capable of holding it. u A suitable path for going on to the scaffold and getting off it must be provided. u