Be Prepared for Life
Activity Kit Six:
Project 9: Building with clay
Most South African don't know how to build durable clay houses. A properly built clay building can last for hundreds of years. Some of our most famous buildings, Groot Constantia and Tuinhuis are built of unfired clay bricks. This is one of the cheapest and easiest ways to build if you have clay and can do it yourself, but avoid building in the wet season!
1. PREPARING THE FOUNDATIONAn unfired clay structure must not stand on the ground or it will absorb water from the soil and slowly disintegrate. Your clay structure needs a dry bottom at all times. Design your building for rounded curves rather than vulnerable corners which may be easily damaged. Choose a site which is firm and hard. If there is too much clay in the soil you will have to build a conventional foundation first, throwing a reinforced concrete slab for your foundation [See Kit 4 : Project 2, Building a surface tank.] We assume that your ground was firm and hard.
Level the intended site. Dig out a shallow foundation and tamp the ground down firmly with a stamper. Cement a stone or fired brick foundation into the position you want your walls to stand in to just above ground level. Cover the ground inside your building with a sheet of damp course running over the foundations of brick or stone.
2. GETTING THE RIGHT CLAYIn Kit 5, Project 8 we learnt how to work with clay. A clay wall needs a lot of clay. The best clay is a short clay with plenty of sand opener in it. To build an inexpensive clay building you need a good supply of clay on or as close to your site as possible. Dig a pit in the ground. Line it with thick builders plastic. Put about 3 wheel barrow loads of clay into the pit and add enough water to foot trample the clay into a workable material.
3. BUILDING WITH CLAY
4. FINISHING THE WALL SURFACESThe biscuit-dry walls are plastered with a 1 part cement : 4 parts sand mixture. Wet the walls well before plastering. Do not plaster below the damp coarse. Finish the rough plastered walls with a sponge for an attractive effect. Paint with this mixture of your own home made paint.
Prepare a solution of 1 x 25 kg bag of white wash [hydrated lime] into which you have dissolved 2 containers of cottage cheese [acts as a binding agent] to fix the white wash. [Under no circumstances use undercoat or PVA paints - the walls must be able to breathe or the clay will become damp and crumble away.] Your home-made paint can be tinted to taste. If necessary this paint can be washed with water when dry.
5. THROWING THE FLOORThe floor can also be made of clay into which peach pips or river pebbles are set close enough to keep feet off the tender clay surface. If the floor is to carry a heavy traffic of feet - use sand and cement. The floor should have a wax polish rubbed into it when dry.
Why not consider building your own Scout office? If you get started and run into a problem contact Keith Struthers of ECOLOGICAL BUILDINGS, 5 Roseway, Constantia. Phone 021-794 7655.
Project 10: Building with sand and cement
In areas where there is no natural clay or there is a requirement for cement buildings, cement block or mortar and mesh structures can be easily built with supervision and significant savings while teaching self-help construction techniques at the same time.
1. PLANING YOUR STRUCTUREHere the help of experts may be necessary especially if you are working in a built-up area where building regulations are very specific. There are two well illustrated publications that are recommended, in this order...
STEP BY STEP BUILDING. BLOCK WORK.
Book 1 - Setting out and building foundations.
For those preferring to work with clay or cement bricks this guide is also available as...
STEP BY STEP BUILDING. BRICK CAVITY WORK.
These publications were available free of change from...
For a less rigorous treatment more suited to rural areas...
PEOPLES WORKBOOK. pp. 476 - 510
This publication can be purchased at a very reasonable rate from...
Environmental and Development Agency [EDA] P.O. Box 322 Newtown, Johannesburg 2113 Phone 011 8341905/6
2. MAKING YOUR OWN BLOCKSMany people are making their own blocks and bricks in Southern Africa today. This requires a mould which can be homemade of wood or metal, or purchased from a supplier.
Soil bricks from clay are made by making a mud of 3 parts of clay to one part of water. This can be well tramped by foot to mix. This mixture can be sun dried, after lifting the mould off the clay brick, and dried over a period or 3 or 4 days.
Soil bricks can also be made of sandy loam and cement using 1 part of cement to 20 parts of soil. Again a mould is needed and there are several different types of moulds and ram presses which strengthen the blocks.
If you want to find out more about these block moulds and presses ask
the following suppliers to send you their catalogue...
3. MORTAR AND MESH BUILDINGSScouts have been using mortar and mesh techniques world wide for at least 20 years and recently through the Scout Human Settlement Programme, implemented through THE WORLD SCOUT BUREAU : AFRICA REGIONAL OFFICE. P.O.Box 63070 Nairobi, Kenya - who can be approached for further details. The technique has proved its worth throughout Africa.
Essentially it is similar to mud and wattle building, using cement and chicken mesh instead. This technique has already been described in some detail in Kit 4 : Project 2, where it was used to build a water tank using weld mesh. A small self-help house does not need to withstand the same pressure and can be built of cheaper materials.
BUILDING THE FLOOR SLABMortar mesh walls are built on a single concrete floor slab which also forms the foundations along its thickened edges. The slab is 10 centimeters thick in the centre and 20 centimeters thick along the foundation edges. It is made of 1 part cement : 3 parts sand : 3 parts stone.
BUILDING THE WALLSBefore building can commence a series of wooden shutters, approximately 2 meters wide by 2,4 meters high made of Masonite with wooden ribs [2 cm square] fixed at 20 cm intervals, must be made. These shutters will form the mould for the outer surface of the walls. They need to able to stand upright by being fixed together externally. No special shutters are needed for window and door spaces as the window and door frames are attached to the shutter and plastered in position as the walls are made. The shutter surfaces are protected when not in use by wiping with old engine oil. A set of shutters can be used to build up to 20 houses, provided they are stored flat on each other under cover and warping is prevented when not in use. In practice the more houses you build, the cheaper the process as the shutters being to pay for themselves, perhaps a whole Scout area needs one set of shutters.
Stretch your chicken mesh tighly over the shutter ribs and bolt the external wall shutters on the foundation slabs in the desired shape. Working from the inside of the structure, apply a thick 4 part sand : 1 part cement mixture by gloved hand to the wooden shutters, working the cement through the mesh to make a wall 2.5 cm thick [first layer]. Allow 12 hours setting time and apply another 2.5 cm layer. The inner surface is finished with a plaster float or a dry sponge. The walls are allowed to cure for 4 or 5 days before removing the shutters. Sprinkling the setting walls with water to slow the curing process allows the plaster to strengthen. While this is taking place the internal walls can be completed.
It is usually most economical to finish the roof with rafters and sheets of light weight corrugated metal with an internal ceiling of plaster board.
Such a structure can be built in about a week with unskilled labour using a team of about 6-8 people. This type of construction could be the basis of much employment in the future of this country and is a skill well worth knowing.
MORTAR AND MESH TOILETSWhere a pit toilet is a necessity, much experience has been gained in rural Zimbabwe in improved toilet design. These directions are for a double latrine structure.
BUILDING A BLAIR DOUBLE PIT TOILETA squared pit approximately 1.9 x 3.5 meters and 3 meters deep is dug out.
The pit walls are brick lined with a cement and mortar grouting [mortar mix 1 part cement : 8 parts sand]. Build a separating wall through the centre of the pit. A level collar of bricks is laid around the top of the pit.
Lay out 2 rectangles of bricks [each enclosing 1.75 x 1.9 meters] on level ground adjacent to the pit and line the enclosed area with plastic or paper.
Place a PVC vent pipe in position and two bricks where the squat hole will be sited. Cut heavy wire weld mesh to fit into these enclosed areas accommodating the pipe and squat hole bricks. Place the reinforcement on one side. Caste a 4 cm layer of concrete [3 parts stone : 2 parts sand : 1 part cement] over the plastic. Place the weld mesh in position, locate the pipe in the slab and top up with another 4 cm of concrete. Smooth the upper surface, sloping the inner surface towards the bricks forming the squat hole [to facilitate washing out]. Cover with hessian and allow the slabs to cure for 5 days, wetting periodically.
Roll the two slabs, over gum poles, into position on the collar over the two halves of the pit. Mortar and mesh walls are made on shutters around the two latrines or on metal forms as discussed in Kit 4 : Project 2. It is vital that no direct light reaches the inside of the latrine and that the doorway is located in such a way that the prevailing wind moves air from the doorway towards the external vent pipe.
The roof is made of thinner, smaller, lighter concrete slabs reinforced with chicken mesh [2.5 - 3 cm thick] which can be lifted into position. No light should penetrate the roof. The vent pipe needs to be 0.75 meters higher than the roof and be covered with nylon mesh screen to keep flies out of the pit, if it is painted black it helps create air currents through the pit.
The floor inside should be painted with black bitumen floor paint and washed regularly. Plant grass around the toilet to prevent erosion.
These toilets are a necessity for the developing world, and another important skill to be learned.
| © Copyright 1991 - 1994
Dr Frank Opie for the South African Scout Association