Scaffold and Ladders

SCAFFOLDING

A scaffold is a temporary structure which supports workers and materials during building and other work. It can be made of steel, aluminium, timber or bamboo.

According to their functions, there are three main types of scaffolds:

• Working scaffolds
• Protecting scaffolds
• Supporting scaffolds

Each type may be erected separately and serve only one purpose. Some situations however, require a combination of two or even all three types.

WORKING SCAFFOLDS

As the name indicates, the working scaffold is used for working from. It holds the worker at a height which enables him to comfortably complete walls etc. when the construction has proceeded to a level that makes it difficult to work from the ground.

The following is a description of two simple scaffolds used to complete walling between door and window frames.

BLOCK SCAFFOLD:

This is the lowest and simplest working scaffold. It is used to raise the worker a bit higher to make it easier to build the wall up to the actual scaffold height of 1,5 m. Set the sandcrete blocks on solid, level ground and lay one or two boards across them (Fig, 1).

TRESTLE SCAFFOLD:

This is a low-level scaffold, consisting of wooden trestles covered by two or three boards (Fig. 2). A trestle is a horizontal beam of wood with two legs on each end. Two or more of them are used to support the boards. Set them on firm, level ground, no further than 1,5 m apart.

The height of the trestles can be from 75 to 100 cm. Small quantities of blocks and mortar can be kept on the platform. This scaffold enables the worker to continue walling up to lintel height, and to erect the formwork of the lintels.

The following are scaffolds which the workers stand upon to reach the higher parts of the construction. The tools and a supply of materials are also on the platform with the worker.

JACK SCAFFOLD

Although it can be no more than 2 m high, the jack scaffold is a satisfactory working scaffold for most jobs in Rural Building (Fig. 1).

The jack scaffold is a dependent scaffold, which means it is propped against the wall for support instead of standing independently like other scaffolds. The feet of the props have to be properly set in place so that they will not move and settle when the scaffold is in use. Never try to put any support under the wall leg of the jack, as this would actually make the scaffold unstable.

Each jack scaffold consists of three jacks, three props and three (approximately 4,5 m long) planks. If the scaffold is to be only 2 m long or less, two jacks are enough.

CONSTRUCTING THE SCAFFOLD PIECES:

The jacks consist of a wall leg and a ledge which is nailed edgewise to the top of the wall leg. Both boards must be at least 5 cm thick by 10 cm wide, and about 100 cm long. The right angle is braced with two ties on each side, in a way similiar to the construction of a large square.

The shorter tie should be set so that it does not cover the corner of the jack, where the prop meets the angle. An opening is left, through which the position of the prop can be checked. The prop has to fit securely into the corner of the jack, without any "play" in the connection. The ties should be at least 2,5 cm thick, and the prop will be 5 by 10 cm by whatever length is required (remember that this scaffold should not be more than 2 m in height).

ERECTING THE SCAFFOLD:

Hold the jack with its wall leg against the wall, and fit the prop into the corner of the jack. Set the foot of the prop securely in the ground. The other jacks are set up in the same way. Check that all three are at the same height and the distance between them is not more than 2 m.

The angle between the prop and the wall should be no less than 30 degrees and no more than 45 degrees (Fig. 3). in soft soil, sole plates must be set under the feet of the props.

SAFETY PRECAUTIONS:

Check that all the members of the scaffold are sound and without cracks.

Check whether the upper ends of the props fit well and without play into the corners of the jacks

Make sure that the feet of the props will not slip. in soft soil, they should be supported by sole plates set in the ground, at right angles to the props (Fig. 1).

Pay attention when you lay the platform boards, so you don't create a scaffold trap. This is a place which looks safe but is not (Figs. 2 & 3 . The free ends of the platform must not project by more than 25 cm past the ledge, and they should be blocked off by a foot-stop (Fig. 4).

Wedges are used between the foot of the prop and the sole plate. By adjusting these, the prop can be tightened against the angle.

Beads can be attached to the bottom of the platform boards to prevent them from shifting along the ledges (Fig. 4), or the platform boards can be nailed directly to the ledges.

NOTE: Always pay attention to the safety of the scaffold. A carelessly erected scaffold is a danger to the lives of workers and passers-by.

BLOCKLAYERS SCAFFOLD

Like the jack scaffold, this scaffold is dependent on the wall for support. The construction is fixed with "putlogs" into the wall, and secured on both sides of the wall with cleats which are nailed to the putlog (Fig. 1).

Erect the standards on top of the soleplate (Fig. 2) and nail the ledger at the required height. Each putlog will have one end in a wall opening which was left during the blocklaying; and the other end is supported by the ledger and nailed to the standard. Secure the putlogs into the wall with two cleats, one on either side of the wall. Make sure that the cleat on the outside of the wall does not project above the putlog, where it will interfere with the platform boards.

Once all the putlogs have been secured, nail braces across all the standards to make the whole construction rigid.

Check the construction, then lay the platform boards. Fix the toe board, and nail the guard rail at a height of 90 cm above the platform.

If a putlog is secured inside ol' a window frame, add an additional strut inside the frame (Fig. 1).

The advantage of this type of scaffold is that it requires le3S wood to make the frame. The holes left in the wall are easily filled with small blocks before the plastering is done.

MEMBERS OF THE SCAFFOLD: (see Fig. 1 above)

• Sole plate - Platform boards
• Standards - Toe board
• Putlogs - Guard rail
• Cleats - Struts (if needed)
• Ledger - Pieces to secure the standards to the sole plate
• (Beads)
• Braces

LADDER SCAFFOLD

This is an independent working scaffold, that is, it is not supported on the building but stands free. A ladder scaffold can be used where the height of the building is no more than 3,5 m.

Three or four ladders are usually used. Erect the ladders on top of the sole plates so that they do not sink into the grourd under use. Keep the ladders plumb and straight, and nail two braces diagonally across the side.

If necessary use some wedges under the ladders to keep the structure steady.

Lay the platform boards and fix the toe board and the guard rail. The guard rail is fixed 90 cm above tho platform.

Before any workers use the newly erected scaffold, make sure that all the parts are well secured and fixed according to the safest manner. Be aware that the scaffold has to carry not only the workmen but also a load of building materials.

INDEPENDENT SCAFFOLD

This is similar to a ladder scaffold with the difference that no ladders are used. Timbers are used instead; these should be 5 x 10 cm by approximately 4,5 m long.

Sort out the timber, keeping the straight pieces for standards and the bent pieces for shorter members like putlogs.

Mark the height of the working platform on the standards, and nail the putlogs to the standards. Erect the standards on top of the sole plates, and nail the necessary braces to the outside of the structure.

Nail two additional boards (ledgers) under the putlogs. These give support to the putlogs.

Lay the platform boards and secure them with nails or battens. Fix the toe board. Nail the guard rail 90 cm above the platform.

If necessary, place some wedges under the standards to make sure that the whole structure is steady. Extra braces can be added to the outside of the structure; secure them to the ground with pegs (Fig. 1, broken lines).

Fig. 2 shows an alternative way to support the putlogs, with a wedge-shaped piece of wood nailed to the standard underneath the putlog.

SUPPORTING SCAFFOLD

As the terra indicates, a supporting scaffold is used to support members of the structure until the mortar or concrete has hardened or cured; or until the parts are assembled, when the member will be able to support itself and the scaffold can be taken away.

The supporting scaffold is seldom used in Rural Building because in most cases a lighter and simpler strutting will serve for the purpose of supporting the usual reinforced concrete members as they are cast-in-situ. See page 167 of the Basic Knowledge book for an illustration of a typical strutting for a reinforced concrete lintel.

The heavier supporting scaffold is used only in cases where the member to be supported is very large and heavy. The supporting scaffold arrangement is shown in the illustration below.

When you construct a supporting scaffold, pay particular attention to the stability of the structure, since it usually has to support very large and heavy members. The distance between the standards (also called struts) must be no more than 1 m (Figs. 1 & 2).

All the shorter braces, which reinforce the connections between the putlogs and the standards and between the standards themselves, are fixed at 45 degree angles. The long braces, which go from the top of the structure down to pegs in the ground, are fixed at an angle of no less than 30 degrees. These help to keep the scaffold from tilting or overturning.

PROTECTIVE SCAFFOLDING

On most Rural Building construction sites, protective scaffolding is not necessary. This is because the structures are relatively low in height. However, when a higher structure such as a water tower is constructed, protective scaffolding becomes necessary to protect the people underneath from falling objects. On jobs where walls are being broken down, or where large and heavy objects are handled, it is advisable to erect a protective scaffold of some sort.

A second platform is made below the working platform, and a side projection is fixed at an angle to this (Fig. 3).

The projecting piece is attached to the standards by wooden braces.

Any tools or materials which fall from the working platform will hit the projecting piece and roll onto the second platform, instead of falling to the ground.

LADDERS

A ladder consists of two lengths of wood, metal or rope, called rails; which are connected at a certain distance from each other by rungs {Fig. 1).

Ladders are used to climb and descend scaffolds, walls, etc. during the construction of a building, and to do light maintenance work from later. Since such a piece of equipment is needed not only during the construction but also later in and around the house, it should be made from sound timber in a proper way so it can be used as a permanent ladder.

CONSTRUCTING THE LADDER:

Both the rails and rungs are made out of Odum. The dimensions of the two rails are 5 x 7,5 x 325 cm, while the ten rungs are 2,5 x 5 x 75 cm. The wood should be straight grained and planed to the above sizes.

Round the top ends of the rails where they touch the wall and cut off the foot ends as shown in Fig. 1, with a 45 degree bevel from each side. To prevent splinters and help the hands to move safely up and down the rails, round off all the edges. incidentally, when climbing or descending ladders, keep your hands off the rungs. Grip the rear edge of the rails.

The over-all width of 75 cm gives an inside width of 85 cm which is wide enough to hold two scaffold boards on the rung. Later we will discuss making a ladder scaffold, in the Construction Book.

The distance of 30 cm between the rungs must not be exceeded, as a wider spacing would make it difficult to climb the ladder.

The rungs are inserted in notches cut in the rails, and fastened by using 75 cm nails as shown in Fig. 2.

Sometimes ladders are reinforced by fastening iron rods, threaded at both ends, through both rails behind the first, centre, and last rungs. The rods are held in place by nuts on the threaded ends.

- NOTE: A good ladder should be treated with oil or another preservative. Dried-out wood is the greatest threat to the safeness of the ladder. Always keep ladders in the shade when they are not in use.