Popular Science Monthly/Volume 41/October 1892/Mud as a Building Material
|MUD AS A BUILDING MATERIAL.|
By WILLIAM SIMPSON, R. I, M. R. A. S.
IT is necessary to premise that under the term "mud" I include sun-dried bricks. When bricks have been burned in the fire, the material becomes entirely changed and ceases to be mud, so I exclude them from consideration in the present paper as a building material. Wet earth made into blocks and dried in the sun differs in no way from a layer of the same laid on a wall. Both methods were used in the East, and often combined in the same building. The reason for this is soon found out if you attempt to raise a mud wall. A layer of two or three feet thick must be allowed to dry and consolidate before another is placed on it, because the weight above would press out the soft material below, and the whole would tumble down. In some localities a layer of mud is put down at the commencement, and while that is drying bricks are made to be placed above.
It was during the cold season of 1884-'85, in traveling through Persia at the time of the Afghan Boundary Commission, that the importance of mud in connection with building and architecture first attracted my attention. I had to pass from Tehran eastward, through Khorassan and into Afghan Turkestan. Along the whole of this route mud is the building material. Some of the serais—that is, caravan serais for the accommodation of travelers—are of burned brick, but these are about the only exceptions. Not only villages, but large towns, are built of mud or sun-dried brick. The defensive walls are of the same material; even such large towns as Sabzawar, Nishapur, Meshed, and New Sarrakhs are fortified with walls of this kind. On realizing this almost exclusive use of one building material, in one region, my mind naturally recalled what I had seen in India, where, although stone and fire-burned
Fig. 1.—The Meshed Gate, New Sarrakhs, on the Heri Rud.
brick are largely used, yet the villages are over very large districts wholly constructed of mud. In Afghanistan it is the same. The fort at Peshawer, which was Afghan territory up to Runjit Singh's time, is a mud one. Jellalabad is surrounded by a mud wall. From the Khyber Pass to Tehran the towns and their defenses, as well as the villages, are almost identical in their material as well as in their general appearance.
These statements show that over a large geographical space in the Eastern world the building material at the present day is almost exclusively mud. I have been thus far speaking of what I have seen with my own eyes. To this may be added the practice of other countries. I believe that it is the same over most of Central Asia. It is now accepted that in Mesopotamia it was largely employed; and we know that in Egypt, from the earliest times to the present day, it has been the principal means employed in structural erections. It was largely used in Greece in ancient times, and also in Spain. It was known in South America and all along the Pacific coast, from Peru to San Francisco. The word "dobies," for sun-dried bricks, is a familiar term—this is derived from the Spanish word adobes. In 1873 I visited the original church dedicated to St. Francis, which gave its name to the now well-known town in California—this church was constructed with "dobies." Mud houses were not uncommon in England in the past, and they are yet known in Devonshire, where the stuff they are constructed with is called "cob." I am under the impression that the importance of mud in connection with building has hitherto been overlooked.
Once begun, the progress of mud architecture would be considerable. Those who began their architectural style with branches of trees could not have made any advance until some kind of implement was invented by means of which the wood could be cut and fashioned; and the "stone age," when stone tools came into use, is a comparatively late one in man's history. The mud builder, on the contrary, required no tools; his hands were sufficient for every purpose. He may have been content at first with an inclosure formed by four walls. A covering of grass or reeds would soon suggest itself; this, although rude and primitive, would be the first complete human habitation. But, more than that, it would be the beginning of the "house"—the "home," which, from the relations and associations it produced, must have been one of the most important steps in the history of early civilization.
The great antiquity of the use of mud as a building material can be established from a number of references to history. In Persia, at least, we have traces of it. Firdusi, in the Shah Namah, relates how Jemshid, now known as a mythical personage, introduced a better civilization among the people; among the improvements it is told how "he taught the unholy demon train to mingle water and clay, with which, formed into bricks, the walls were built, and then high turrets, towers, and balconies, and roofs, to keep out rain, and cold, and sunshine." It is naturally inferred that the bricks made by the children of Israel in Egypt were sun dried from the use of the straw in them. The making of bricks is often represented in the sculptures of Egypt.
The first use or invention of mud for building was ascribed to mythical personages, thus attributing to it a kind of divine origin.
I shall now give a few details of the manner of building in mud, most of which are derived from what I saw in Persia. Many of the methods I saw there I have since found are also practiced in other parts of the world.
It was pointed out to me that, in the larger towns, on entering a house, you have often to descend from the level of the street to the ground-floor. It was explained that this results from utilizing the earth on which the house stands, thus saving the expense of transporting the building material from outside the town.
In good houses a foundation is laid, varying from two to four feet in depth, formed of rough stones or broken fire-burned bricks, and piled up with mud and lime. This is carried up a foot or so above the ground, before the mud wall is commenced. In villages, where everything is rude, this foundation is made of any kind of rubbish that is found handy. This is a very interesting feature of mud architecture. Its object is no doubt to give strength where the wall would be liable to friction from the street traffic; and probably to prevent to a certain extent damp from rising. It would also be a safeguard against another serious danger—that is, if water were to accumulate by any chance round the base of the mud walls, and remain long enough to soak through, a very serious catastrophe might take place from the house tumbling
Fig. 2.—Mud-built Houses, Village of Sivah, Khorassan.
down. I can not recall to my memory any foundation of this kind in the mud houses of India. Village houses in the northwest of that country are usually built on a chabootra, which is a raised platform of mud, about a couple of feet in height, and this forms the floor of the house. This platform, by raising the foundation of the walls above the ground, may perhaps serve some of the purposes of the layer of stones in the Persian foundations.
The walls of Persian houses vary from two to four feet in thickness. This depends entirely on the quality of the house and the means of the builder. Thick walls make a cool house, and that is a desirable thing in the climate of Persia. If upper rooms are required, a greater strength of wall will be necessary. The mud is either laid on in layers or in the form of bricks. In garden walls hollow bricks are used for the top, to give lightness. These bricks are called sanduk, a word meaning "box," which is descriptive of their character. The tendency in mud-building to produce thickness below in the walls, and lightness above, is most marked in the walls of villages and towns. These are all built with a visible batter. The earth taken out to form the ditch gives an abundant supply of material for a town wall, and a thick, solid mass at the base is necessary to give strength to the defense. Where wood is plentiful, as in the province of Mazenderan, flat roofs are the rule. In large districts of Persia wood is scarce.
Fig. 3.—Tomb, constructed of Mud, with Dome.
I understand that south of Tehran there is very little timber, and there is also great danger from the white ants, so the vault or barrel roof is the usual means employed. According to Strabo, it was the same in Mesopotamia; he says, "All the houses are vaulted on account of the want of timber." These vaulted roofs were frequent enough along the route I traveled. I have seen whole villages with them. Square buildings would have a dome; and a semi-dome at one end of a barrel-roof seemed to be a favorite method in that part of Persia. What struck me with surprise was the facility with which these villagers could construct such roofs. If there was any irregularity in the plan of the house, the barrel-roof was extended or drawn in, as the case might be, to cover the space. Of course, in the villages it was all a very rough-and-ready kind of work, evidently done by no better principle than that of rule of thumb. I was still more surprised when I learned that these vaulted roofs were constructed without centers.
In Persia the mud walls are covered over with a mixture called kahgill, which is composed of mud and chopped straw; this serves to prevent the rains from washing away the walls, as it hardens the surface. The application of this mixture is generally repeated every two years.
The general impression in most minds will no doubt be that mud-building only belonged to a rude condition of civilization, and produced houses that were little better than hovels. I have now to point out that this manner of building was developed into a highly decorative style which in itself would entitle it to a place in the history of architecture. This position, it appears to me, has been almost entirely overlooked by those who have written histories of architecture. Architectural writers always treat upon primitive wood constructions, because forms can be traced from it up to the highly developed styles of Greece, Egypt, and India. The same process can now be gone through with the primitive mud as a building material. At present my purpose is to show that it was carried to a pitch of finish and refinement that
Fig. 4.—Persian Mid Village.
rendered it worthy for the palace or the temple. The following letter sent to me by General Sir Charles Wilson would in itself be a sufficient evidence. Sir Charles is well acquainted with western Asia, and, being an engineer officer, he may be trusted as an authority. He says: "It may interest to you know that in Anatolia there is much mud-building; and that most of the great buildings of the Seljuks, more especially their great palace at Konieh, were of mud faced with glazed tiles. Some of the minarets of their mosques, built with sun-dried bricks, arranged in patterns and faced with glazed tiles, or with the ends of the bricks glazed, are extremely beautiful in their decay. The Seljuk architecture is Persian with a development of its own." Here are mosques, or temples, and a palace constructed with sun-dried brick, which are declared by this high authority to be beautiful even in their decayed condition.
A somewhat similar development was reached in Peru, but with different materials. Squier, in his Land of the Incas, describes the palace of Chimu, where the adobes, or sun-dried bricks, were covered with stucco, on which beautiful arabesques were produced in relief. From these ornaments he calls one of the great apartments the "Hall of Arabesques"; of which he speaks in warm admiration, and adds, "No description can give an idea of the character of these rilievos." In describing other ornamentation of the same kind, he says, "Here, as elsewhere, there are traces of color."
I understand that the higher developed condition of this style of architecture in Persia was attained by covering the mud walls with glazed tiles. The tiles, it must be understood, were covered with ornament.
The interior of a mud building may also be decorated with glazed tiles; but in Persia gatch, or gypsum, is plentiful, and where ornament is required it is much used. In an old tomb, at Sarrakhs, I saw some particularly good ornament in this material; and it appeared to me to be all hand-work. I chanced to come upon one room that impressed me with the capabilities of this manner of decoration. It was at a place called Mazinan, on the first march eastward within the Khorassan frontier. There appeared to be the remains of more than one town here; I strolled over to that which was nearest, and found that it was all formed of mud. The mass forming the mound was artificial, for I found bits of red burned bricks or vessels imbedded in it. The top was a curious maze of rooms, courts, stairs, and roofs, much of it in a tumble-down condition. The solid mass of mud or earth was about twenty feet high, and the houses were above that; still, they were not all on the same level, for I went up and down short flights of steps. The whole was of mud or sun-dried bricks. The mud must have been carefully put on at first, but the high finish was produced by gatch, or gypsum. There were very handsome niches all round the walls, and the fireplace had been elaborate, but some act of destruction had taken place, and the fragments lay on the floor where they had fallen. The ornament was simple; there were some slight moldings on the space between the niches. Lines had been drawn into the gypsum, and an ornament had been repeated by means of a stamp which had been pressed or imprinted when wet, producing a raised pattern; the impression left was so clean and perfect, it might have been gilt, and it would have been quite equal to the work we have at home on picture-frames.
Mud was the exclusive building material of that part of the world. The simple houses of the villages are formed of it; the defensive walls of the towns, which, owing to the Turkomans, were an absolute necessity to every village, were constructed of
Fig. 5.—The Mud Walls of Nishapur, Khorassan.
the same. The houses of the rich were also formed with it, and it had been developed into a highly decorative style of architecture.
One would not expect much durability from such walls, yet I was informed that there are walls of sun-dried brick in Ispahan which are over three hundred or four hundred years old. This quality of durability will no doubt depend upon the character of the soil. In the northern part of Persia, according to Mr. A. Finn, of the consular service, the walls of the old city of Erig are still standing, and they are said to have existed for twelve hundred years. There still remains at Cacha, in Peru, a wall of adobes, or sun-dried bricks—part of the Temple of Viracocha, which was in a ruined condition about three centuries ago, when Garcilasso described it, and this wall is still standing to a height of forty feet. There are the remains of very old walls in Egypt. There is a Devonshire saying regarding the "cob," or mud walls, of that locality, "A good hat and a good pair of shoes is all that cob wants." The pair of shoes here meant is a stone foundation such as I have described in the Persian houses—that is, to protect the lower part of the wall; and the hat is a sufficient amount of thatch, or covering, to the top of the wall to save it from the influence of rain. With such conditions, I believe that mud walls in Devon, even in our own damp climate, have stood for long periods of time.
The sloping jambs of doors and windows are peculiar to many old styles of architecture, such as the early Greek and Etruscan. Theories of origin for this have been often suggested, but we have no difficulty in accounting for them, if we suppose that the narrowness above was a form, and the natural result of the sloping walls of mud.
I have already explained how builders in mud—and which is well exemplified in Persia—construct their walls with a broad base, to give solidity below, and with a marked batter upward to reduce the weight above. It has been suggested—and, I think, with every reason in its favor—that this explains the very marked slope of the perpendicular lines of the Egyptian pylons. All the authorities agree in stating that in the old temples the outer wall forming the temenos of temples of Egypt was made of crude brick, and as the pylon was the gate through this wall in front of the temple, the great probability of its being constructed of the same material is obvious.
When I had seen village after village in Persia with vaulted or domed roofs, and learned that such roofs could be formed without centers, the idea immediately suggested itself that these methods of building had existed from the most primitive times. While the necessity for wooden centerings for building vaults and domes was believed in, we never could have credited an early state of civilization with this invention. Let this assumption regarding centers be removed, and the whole problem is changed. The earlier workers in mud or clay could not have been long in discovering how to spread their material over the space inclosed by four walls. They would, no doubt, have begun at first with small spaces, and a very little experience would soon have enabled them to deal with greater. If any one considers the matter, I think he must arrive at the conclusion that mud must have been first used for a long period of time before burned brick came into existence; and now that we know how easy it is to produce a roof with the mud, there is no great improbability in the assumption that the vault or dome, as well as the arch, all date back to a period when that material alone was in use.I have described the foundations of a mud wall, such as they are in Persia, formed of burned bricks or stones and lime; and also
in Devonshire, where they are known as a "good pair of shoes," because they protect the feet, or lower part of the wall. In the remains of the Temple of Viracocha in Peru the mud walls have a stone base eight feet in height. With these examples before us, and understanding the necessary purposes they served, we may assume that such protective substructures were generally employed wherever this particular manner of building was in use. It is highly probable that in this rude constructive detail we have the first origin of that part of the architecture in the palaces of Assyria to which the great winged bulls in the British Museum belonged. It seems now to be accepted that these palaces were constructed of crude brick, or at least this material was the principal one employed; baked or perhaps glazed brick may have been used in the exterior of the walls, but the interior was of sun-dried brick, and covered with stucco. This latter part is exactly what I saw in Persia. Along the base of these walls slabs of marble were placed, varying from three to about eight feet in height. These were generally sculptured, and the great bulls were represented on the portions of the slabs on each side of the doors. The development of this highly ornamental dado in the palace, from the base of the mud wall, is not a difficult problem to solve. The foundations I saw in the villages were formed of stones, halfbricks, or rubbish of any kind. In the better class of houses a more regular construction would be followed; and in palaces the covering of this with marble is what might be expected. I accompanied a visit of ceremony to the palace of one of the Shah's sons in Tehran, and I noticed that, in the room where we were received, slabs of alabaster, about three feet in height, went all round the base of the walls. These alabaster slabs in Persia are the counterpart of the marbles in the palaces of Assyria. In both cases they served the same purpose—they protected the lower part of the walls.
It was a source of some surprise to me to find that the Persian villages were, as a rule, exactly similar to those I had seen in the Khyber Pass and other parts of Afghanistan. They are square, formed with four high crenelated walls, and a round tower at each corner. The gateway is in the center of one of the walls, and the mud houses are huddled together inside, one might say, "anyhow." Larger villages may have six or eight towers; small towns or large ones have more wall and a larger number of towers. One of the first things that drew my attention to mud as a building material in Persia was, when in passing a small town one morning on the march, I saw some men either building or repairing the walls and towers of the place. It then struck me that these defensive walls were, with only some trifling details of difference, almost identical with the walls we are so familiar with on the Assyrian sculptures. There is the same repetition of crenelated wall and tower, and constructed of the same material. I said to myself, "These men, in the present
Fig. 1.—Stone Door, Lasgird.
day, are building an old Assyrian wall of fortification." Such defenses must have begun at a very early date in Mesopotamia, long before the sculptures were produced from which we know what they were in appearance, and their construction has never ceased from that to our own time. This presents a very striking illustration of the continuity of type.
About one hundred miles east of Tehran, there is a curious village called Lasgird (Fig. 6). It is supposed to be very old, and its circular plan is said to have been first drawn on the ground by Las, the son of Noah. The statement has already been made that the villages in Persia are square; such is the rule, and it will explain so far how a round one in their midst appears as something strange and remarkable. This great circular wall is so massive that the houses of the people are constructed on the top of it, and form in a rather irregular manner two stories. There are rude balconies, or I ought to say narrow ledges, on the outside which form communications. These are made of untrimmed branches of trees interlaced with twigs, on which mud is laid, but without a protective railing of any kind. The interior space formed by the circular wall is filled with storerooms and places where the cattle can be safely housed in case of an attack from the Turkomans. The only entrance into this strange structure is by a small opening about four feet by three, which can be closed by a stone door turning on pivots. The smallness of this doorway was intended to prevent raiding enemies from entering during the chances of a rush, for it would be necessary to keep it open to the last moment to admit those of the villagers who were running home for protection.
I have dealt with this building material in the past; regarding its future I can say but little. In England here it was largely in use, so was wood, and that which is well expressed by the words "wattle and dab," which might be described as a combination of wood and mud. All these, as our material conditions have improved, have been slowly supplanted by the burned brick or stone. "Cob" is still in use, to a limited extent only, in north Devon. It may be assumed that it is not suited for our damp climate. In dry climates, such as Persia and Egypt, it is likely to continue, for the simple reasons that it is a cheap material, and that a comfortable dwelling can be made from it.
I might mention a country like California as one where this material might be valuable. California has a dry climate. When I was in San Francisco, in 1873, that town was almost wholly constructed of wood. Stone was feared, owing to the chances of earthquakes. While there, I visited the church of St. Francis, built of adobes a century before, and it had stood firm and secure all that time. It occurs to me—but I have no right to speak as an expert—that a house built of thick mud walls and wooden joists and rafters would be tolerably safe during an earthquake, unless it was a very severe shock; such a house would also be safer than a wooden one from fire, which has always been a great danger in San Francisco.
- Bricks of this kind, "when placed one upon another after being imperfectly dried, combined, under the influence of the weather and their own weight, into one homogeneous mass, so that the separate courses became undistinguishable. This latter fact has been frequently noticed in Assyria, by those who had to cut through the thickness of walls in the process of excavation." Perrot and Chipiez, A History of Art in Ancient Egypt, vol. i, p. 113.
- Adobes, or dobies, is probably a variant of the Arabic tob or toob, allied again to the Coptic tobi, which was also the Egyptian word for brick.
- Sun-dried bricks are called khest in Persian; the fire-baked bricks are ajur or aujur. In Afghanistan, khist is used for both burned and unburned bricks. Gill, with a hard g, is Persian for mud.
- This recalls an old practice of Eastern architects, in constructing domes with pots, thus producing a considerable reduction of weight, and consequent diminution of thrust. A well-known example of this is the dome of St. Vitale, at Ravenna.
- The word is kah = straw, and gill = mud. In Indian villages the mud floors are washed over with a thin mixture of mud and cow-dung.
- Peru, or the Land of the Incas, p. 135.
- Ibid., p. 154; also at p. 411.
- Squier's Peru, p. 407.
- Gird in this word is said to have the same signification as "girdle" in English—which may be rendered as "circle."
- The author might have dwelt, to a greater extent than he has done, on the mud buildings of North America, which are abundantly exemplified in the adobe structures of Mexico, California, and New Mexico. As it is, he only refers to them incidentally. The log-cabins of our early settlers were of a mixed construction, in which the "dabbing" of mud played nearly as important a part as the framing of logs.—Ed.