Living in the Environment, Appendix 1, Planning for mud brick

Appendix 1, Planning for mud brick

Author: Alistair Knox

The walls of more than half the domestic buildings in the entire world are reputed to be built out of one or another form of unbaked earth. The majority of course are in Asia, Africa and South America, but there are a great number of earth buildings in Europe and North America as well. They are nearly all primitive building systems but today they could become much more sophisticated if required. Even in ancient times there were important earth buildings. The Lima Cathedral is the biggest mud brick building in the world with walls five feet thick.

The aim of mud brick building should be sufficiency rather than efficiency.

There can be a tendency to stretch its capacity to an unsafe structural level when there is no reason at all to do so. Well planned earth design should not take unreasonable risks - remember it is only dry mud after all. Its wonderful natural qualities make it therapeutic to use and to live in.

After twenty-seven years' experience in the field I am confident that even in conservative Victoria it is now possible to build in earth anywhere in the State, provided the right attitude is adopted towards building authorities. Some building surveyors have had no experience of adobe and as their work is to administer an Act for the structural stability of buildings they are naturally suspicious. It is not wise to argue with them but rather to use the provisions in the Uniform Building Regulations which will allow intending applicants to lodge plans in such a way that they will conform with their technical requirements.

Building plans should be reasonably simple in character, that is, the walls in general should not be unnecessarily high unless there is some special architectural reason for it. Australian buildings look more at home when they employ the worn-down timeless character of environmental design. If earth walls are over twelve feet high they are better used as in fill walls with posts appearing at modular intervals to support the roof structure in a system of point loading.

Adobe block or mud brick construction is the simplest because it eliminates uncertainty and technical difficulties and its stability can easily be proven. pisé de terre the other major earth wall method is more monolithic than mud bricks. It consists of slightly dampened earth rammed between forms. The walls are generally about fifteen inches thick. Initially it seems to be an easier method than adobe but its shutters limit its design potential and the ramming technique adds to the possibility of structural instability unless it is expertly done.

In contrast adobe or mud bricks can be undertaken by beginners with relative safety, providing it is approached in a common sense manner, because the properties of the bricks are known before they are built in. It is a good plan to consult a sympathetic structural engineer when planning to build in mud bricks. Do not ask him what to build because engineers as a race are not architecturally inclined. Instead ask him to show you how you can prove to a building surveyor that the structure you are contemplating is structurally stable. It is important if the building is of any dimension to consider whether or not an architect should be employed, and it "is a subtle question that depends on the competence of the individual architect in the end.

Architects can be visual and superficial rather than structural and fundamental. Choose a planner with his mind in the heavens and his feet on the ground. Many sensible people can with some effort, design a building that is both economic and suitable but they should take the precaution of having a good structural man examine it before they proceed. Remember also that a house is often the most expensive thing we ever do and we should be as certain as possible that our design is both creative and practical.

A lack of knowledge can prove very expensive. Experience may teach how to make economic decisions but it requires vision to produce a good design.

A sensible engineer would ask the builder to make some bricks from samples of the materials he intends to use and get them tested for crushing strength, and possibly for water penetration. Our experience has shown that the usual mud brick in the Eltham area crushes at over 200 pounds per square inch even when bricks are made in the simplest possible manner. Anything over 100 pounds per square inch is adequate for normal residential work for walls up to ten feet high if the walls are ten inches wide. The engineer's job is to show how the walls will support the weight to be placed on them. If he is doubtful he can provide posts at modular intervals so that the roof may be point loaded to satisfy any building surveyor.

Should the building surveyor reject it through ignorance or prejudice he can submit the plan to the Uniform Building Regulations Committee which will adjudicate in his favour if the engineer's details are correct.

Concrete slab construction is generally used for mud brick building because the site is often levelled for material and it enables the walls to be kept at a minimum height from the ground because there is no sub floor brickwork. In any case slab construction is almost essential to good modern design. If the site is well drained and spacious, excellent economies can be affected by deleting the slab altogether. This method provides for pouring concrete footings to an accurate level contiguous with the previously excavated ground line. One course of standard pressed bricks are then laid on the footings to form the exact ground plan of the house. Assuming the earth walls are ten inches wide the brick base should also be ten inches wide. Two bricks laid side by side separated by one inch will provide a ten inch wide plinth. The one inch opening between the bricks should be filled with mortar. The resulting three inch rise the bricks provide that will occur under the walls of the building make a natural shallow dish into which brick, paving slate, titles or other hard type floors may be laid so that they finish at the correct floor level. Where the building is situated partly on filled ground it is necessary to construct a pier and beam footing in the usual way or as designed by an engineer.

It is good practice to construct structural window walls to support the roof.

These windows can be home made. As earth has a rugged and durable character second hand timber may be used. It unites naturally with the walls. I generally use stud wall, solid timber, brick or other forms of construction for at least some of the internal walls, but this is from preference rather than necessity.

There is still every good reason to use internal walls of earth also because of their temperature control and sound proofing, as well as their natural sculptural beauty. Chimneys can also be constructed entirely of earth. In the first house I built for Dick Downing and Dorian Le Gallienne the chimney was of earth and it has lasted for more than twenty years. I find it is generally better however to build them from stone or hand made bricks. It takes away a sense of uncertainty that may cause clients to feel uneasy about them. Internal mud walls should always employ heavy adzed lintels over doorways and weight-bearing arches. Nothing gives a greater sense of well being. The same goes for great open fire places where enormous timber lintels are used over openings instead of concrete or steel. It emphasises the primitive power of the material and is aesthetically most satisfying to look at.

Adobe structure and environmental design go hand in hand. They combine to produce buildings of strength and character in the simplest manner. It is important not to ornament earth walls except in an integral way that exploits the natural characteristic of their thickness, and their flesh-like surface and patina. Well placed pierced mud walls can show the thickness of the walls and add architectural punctuation. It is necessary to be discreet in this activity lest the building starts to look like a brick veneer imitation Spanish Mission house. Persian rugs and wrought iron can create a whole new aesthetic dimension when used with earth walls.

Mud buildings should also have something cave-like about them. The use of sheet plaster ceilings in conjunction with mud is a denial of principles. They are totally alien the one to the other. The only possible plaster application is that which exposes the raw reverse side especially if it is painted over with an application of mud wash.

Earth walls should always be rendered with flexible materials and the use of cement must be avoided. Cement cracks in time and allows water to penetrate between it and the earth walling so that it can break off or become permanently damp and crumbly. Most cement rendering also looks out of keeping with the subtle texture of the earth, which is one of its major qualities. Cow dung mixed fifty-fifty with a binding type of top soil makes about as good a render as is possible to achieve. It is both durable and beautiful and allows personal interpretation of application.

Our painting contractors use a variety of finishes on external mud brick walls based on PVC glues, Bondcote and other proprietary lines. They seem fairly adequate but there is a tendency for them to crack on the north or sunny side of the house if there is any dampness left in the wall. Probably experimenting with the particular soils concerned is the best way as any of arriving at a satisfactory conclusion. In the early days, we used lime washes which gave beautiful white walls. Sonia Skipper had a genius for slightly colouring these so that each wall was subtly different from its opposite number. The end result was one of timelessness of building finish. Whitewash mixture was 20 parts white cement, 1 a parts limil, pigment and a handful of rock salt. A little experience in whitewashing may cause a variation in this mix according to the texture of the wall. Large plain surfaces can be sprayed.

In my own opinion it is not really necessary to apply any finish to external walls if the base material is of a good strong character and reasonably sheltered from the strongest elements. The fretting that will take place is so slow that the passing years will give it an artistic spirit. If for some reason the wear becomes too much at some odd points rendering up with mud and cow dung for an hour or so will get it back to where it started years earlier.

There are so many different methods of making mud bricks ranging from single moulds and clay hole to a highly complicated machine method. The simplest was that which was used in Eltham when we first began when water was also a serious problem. A shallow hole was dug that reached into the clay subsoil and then water was put into it, to say four to six inches in depth. The sides of the hole were widened by being broken back into the water and the water would percolate up through the mix. It is generally better to let the water rise up through the earth than place it on top of it. It generally takes about a gallon to puddle a clay brick fifteen by ten by five inches. The water should penetrate the whole of the clay which has been fairly well broken up, so that the mixture can be extruded between the fingers if a reasonable pressure is applied. The trampling over it breaks it up and the whole becomes quickly plastic. Before the days of tractors, horses were used for puddling clay for bricks. An area would first be ploughed then have straw scattered over it. The driver would stand in the middle of this space and with long reins walk a team of horses through it until it was thoroughly mixed ready for placing in the moulds.

I once recall Danila Vassilief the sculptor, who had a good knowledge and experience from building some exciting buildings in mud and stone at Warrandyte, telling me how in Eastern Europe the Gypsy women would take over when the horses had trampled the mud. The man in charge would scoop up a shovel full of wet clay and push it into two small brick forms (probably not much bigger than ordinary brick size) that the women set on the ground. They worked in bare feet. As soon as the moulds were filled they would jump on them and with a quick flick both press down the clay and level the surface at one gesture. They would then pick them up by the handles and scurry off to the place prepared to turn them upside down and empty out the brick for drying. He said they could make six hundred of these small bricks a day. It must have been before the time of Women's Liberation movement.

Tribute could be paid at this point to the fascinating personality of Danila

Vassilief himself, and to his building projects. He was one of the early post-war group of artists, and spent the last twelve years or so of his life in Warrandyte ana Eltham. He was an art teacher at Koornong school when I first met him. Later he built in stone at his nearby property called 'Stonygrad'. This was one of the most remarkable buildings I ever saw. It was really great sculpting, with powerful rugged stone walls and enormous tree trunks forming the main beams of the ceiling and roof. They ran at about seven foot intervals along the length of the rooms for about twenty-five feet. Over these beams lengths of saplings about 6 inches to 9 inches in diameter were split in half were turned split downwards to form the ceilings. The roof seal was concrete spread over this structure so that the resultant building viewed from above looked rather like strangely formed cement mushrooms of enormous size. The roof developed leaks in course of time, and the last occasion I went by there some years after his death the whole had been covered over with corrugated iron. It was one of those occasions when that roof covering gave me no pleasure at all.

Danila was altogether a special man with his sculptings and paintings and his teaching abilities. He was even able to use fly wire in such a way that it read in the building as sculpture.

He had started life as an officer in the Cossack army and left rather hurriedly after the revolution of 1917. In Australia among other things he built eight miles of railway in the Northern Territory and seemed to crowd energetic excitement into his whole life.

Shortly before his death when he was teaching at Eltham high school he used to plead with Margot and I to go fishing with him for Murray cod on the Murray River at Robinvale. Looking back I am very sorry I did not go at least once, as these are the things that once gone can never return. Beside the quiet flowing river I would no doubt have learned more secrets of earth building and of life generally.

Farmers are good people for producing mud bricks in number and at low cost because of the space in which to work earth moving machinery and generally because of the choice of soils they command. In addition they are practical and I have found they generally contrive individual ways of producing the age old commodity the Egyptians designated D.B.T. in their hieroglyphics and which is now called adobe in South America or in Australia, plain mud brick.

At Cobungra for example, the sheer dimension of the land suggested a system which provided all the bricks required for that large building in a few days. The house was on a low hill. The top of it had been levelled and it fell away gradually on all sides. Various earths had been examined for suitability, and one was selected from about a mile away that was binding when wet but quite friable when dry. This material was carted to the site. It was not a heavy clay soil and therefore did not require much straw added. It was carted in large truck loads, and water from the nearby lakes we were making was pumped into it. The front end loader mixed the wetted soil into a consistent plastic mass and then carried it around the site to appropriate points where men using the single mould method and working on contract were able to produce two hundred and fifty bricks per man per day.

The reason was that the soil was already prepared and of character that slipped easily out of the mould. The grass on which they were made had been recently cut and this permitted the water to drain away quickly, and left a good bottom on the bricks. The form itself was slightly wider at the bottom than the top. The unobstructed site caught the prevailing winds and it was soon possible to turn out the bricks on edge. As soon as a brick can be safely turned on edge it is practically speaking a viable mud brick although it is still only half dry inside. Getting it on edge speeds the drying process. When the bricks were completely dry they were loaded on to the scoop of the front end loader then driven back to the building site and placed at the required point. It was a good example of minimum physical effort for maximum results.

Not a few would-be mud brick makers have foundered on the rocks of difficulties of brick production. The popular fallacy that mud bricks cost nothing can be a real delusion. It must be clearly remembered that time is money when making mud bricks. It can mean aching backs, slipped discs and other things also if not done intelligently.

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