Last edited 31 Oct 2021

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Institute of Historic Building Conservation Institute / association Website

Mud brick in Iran

Although mud brick is no longer a popular building material in Iran, the skills and knowledge of how to use it are essential in maintaining the authenticity of earthen architectures.

Bidih.jpg
Bidih, an ancient neighbourhood in Maibud.

There is no question that earth is the oldest and the most widely used of building materials. The earlier bricks were not fired but dried in the sun. The oldest sun-dried brick so far discovered dates back to about 8000 BC. It was shaped by hand, as evidenced by the fingerprint marks on it.

In Gandj-Dara, near Kirmanshah (Iran), walls in level E were constructed of plano-convex and cigar-shaped mud brick dated possibly to the late 9th and early 8th millennium BC.[1] This type of brick is evident in the elongated handmade bricks at the site of Jericho in the Jordan valley.[2] Tell Aswad in Syria (8th millennium BC) and the Indus valley cities of Buhen, Mohenjo-Daro and Harappa show a similar reliance on mud brick. This was also the principal building material in Egypt, where from antiquity until modern times mud bricks were made of Nile mud, a mixture of clay and sand, sometimes mixed with bits of straw or animal droppings.

The geography of this article relates to the oasis cities and towns on the fringes of the central Iranian desert, where the irrigation system featured the qanat (an ancient technique for supplying water from the underground water table at a higher level to the oases by an underground channel system), and where the building material was essentially earth. Soil is the most readily available of materials from which earthen buildings are built. This is normally sourced by nearby digging, costing virtually nothing. The manufacture of mud brick is simple: soak the earth in water, add chopped straw, mix with bare feet before moulding one after another, row after row, and leave in the sun to dry.[3]

After one or two days mud bricks were usable for construction in combination with fresh mud mortar. The use of an identical ingredient for mud mortar, mud bricks and mud plasters was fundamental to making a homogeneous structure strong enough to survive over millennia. Being mixed with straw, the mud bricks of archaeological ruins are highly regarded by farmers as fertiliser for farming. As such, earth materials can easily return to nature. That facilitated a process by which an entire built-up area, once it becomes derelict, could be turned into agricultural land. So after a few decades of farming activities it is difficult to find occupational debris remaining from the previous settlement. Examples of this are found in some parts of the Kazimabad and Badrabad neighbourhoods in Maibud, abandoned initially by the shortage of qanat water, or the entire Dih-Nu neighbourhood may have been affected by flooding.

The assumption that earth buildings are impermanent is clearly erroneous, as demonstrated by the survival of ancient middle-eastern archaeological sites. In the Yazd region, buildings a few millennia old remain and houses from as early as the 14th century are still in use. At archaeological sites the homogeneity of the earthen wall and its durability over millennia has sometimes made it very difficult to distinguish ancient walls from virgin soil. The flexibility of earthen structures facilitated changes and repairs.

As Georgina Herrmann argues: ‘Walls are cut down or rebuilt, doors opened or closed. Floors become uneven and are raised by a new layer of rammed earth. Storage pits are cut.’ Trying to distinguish original fabric from later repairs and additions is a complex operation, particularly where part of a wall has fallen down.[4] Such adaptability within an urban landscape, which developed over millennia in a small geographical area, resulted in a recurrent process of reuse, extension, adaptation and mutation, making it very difficult to establish a chronology.

In contrast to stone-built environments where stones of different sizes, colours and from different quarries are used even in a single building, mud bricks have evolved a rather standardised form in terms of both shape and dimension. Earth is sourced from the closest available soil, and there is no major difference between the quality, colour and techniques used in mud bricks of a given period in a particular region, or more generally in mud bricks of different periods of the same region. That contributed to the integrity of the earthen urban landscapes, despite its diachronic development. Furthermore, the successive mud coatingrendering exteriors and insulating roofs with mud mortar − refreshes the appearance of an already 2000-year-old structure in the same way as a 20-year-old building. That adds to the complexity of the interpretation, and to its impact on the site’s authenticity.

Variations in quality, colour and texture of mud bricks used in different periods are less discernible than variation in size. Since mud bricks are handmade and produced locally, there might be slight regional variation. Concentrating on a particular region with shared historical, socio-economic and geographical characteristics may help to identify a chronology for mud bricks on the basis of their dimensions.

As in modern times, the size and shape of the brick was largely standardised in the past, although there was variety over time. In contrast to the gradual reduction of the size of mud bricks in Iran, in Britain bricks increased in size from the medieval period onwards. Medieval bricks were characterised by poor quality and excessive water content in the clay, which required longer drying, and meant that bricks had to be small and thin enough to dry evenly.[5] Fired bricks need fuel, kiln and transport. Most important, they were subject to the brick tax, which could influence their size. By contrast, mud brick is local, the ingredients and production were very simple, and the approach has hardly changed from ancient to modern times.

Compared with modern construction methods, traditional earthen architecture followed a disciplined schedule of construction in relation to the seasons and climate. To maximise structural strength, it was crucial to have a seasonal timetable for building activities. This depended on knowledge of how weather affected the manufacture of mud bricks; of when best to construct foundations and walls; and in what climatic condition domes and vaults were most successfully formed. Indeed, each phase of the building process was undertaken at a specific time. So specific was the relationship between building stages and climate that construction was suspended at some points in the year, partly because of the weather and partly because pauses were required to allow the structure to settle. This was also consistent with agricultural works in the region.

For example, in the Yazd region, Aban mah (mid- October to mid-November) was deemed the best time for the application of kah-gil plaster and for the insulation of roofs. The gentle autumn weather allowed the thin layer of plaster to dry slowly, without cracking, as it would do in the hot summer or cold winter weather. Following the completion of this robust construction process, proper insulation could be installed for the protection of roofs just before the onset of winter.

There used to be a calendar and an unwritten timetable for earthen construction activities, based on the climatic conditions. These calendars varied locally according to climatic variations across different parts of Iran. There are no such climate-based considerations in current conservation practices for earthen buildings since everything is premised on available financial resources, which have little correlation, if any, to the seasonal nature of building. This has a direct influence on the final resilience and strength of the structures.

Earthen building is more skill-based and labour-intensive than building with other materials. The construction method does not easily lend itself to mechanisation, and tools have less of a role. From the simplest activities, from the spreading of mortar on the courses of mud bricks to more complicated actions such as the construction of vaults and domes, all work is done essentially by hand. The understanding of traditional techniques and skills was acquired in the past by masters and craftsmen. Handed down from generation to generation, it remains central to developing reliable and sound conservation practice.

In Iran the knowledge and understanding of earthen architecture is declining. Although mud brick is no longer a popular building material, it can play a significant role in maintenance, conservation and reinforcement of the mud brick structures. The traditional knowledge, skills and high-quality workmanship are part of the less tangible heritage and an irreplaceable source for maintaining the authenticity of earthen architectures.

References


This article originally appeared in Context 143, published by the Institute of Historic Building Conservation (IHBC) in March 2016. It was written by Eisa Esfanjary, assistant professor of urban conservation at the Art University of Isfahan.

--Institute of Historic Building Conservation

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