A7 Mud brick walls. Mediterranean Area 1/6 PRÉSENTATION. Geographical Influence. Definition. Environment. Illustrations.

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1 Building techniques : Country : A7 Mud brick walls Mediterranean Area PRÉSENTATION Geographical Influence Definition Mud brick walls - Denomination: brick/adobe -Raw material : earth (mud / clay) -Bricks are shaped / moulded before laying -No baking : mud elements are dried in the sun. -Bricks are homogeneous in size and height, laid straight -Bricks are laid in mortar Environment The use of mud brick has been reported in all countries of the Mediterranean area, except Israel. This building technique is found in all rural areas, in each country.it is sometimes but seldom found in urban areas in certain countries. It is usually found in plains, but can occasionally be found in mountain areas or seaside areas. General view: Detail close up : 1/6

2 CONSTRUCTION PRINCIPLE Foundations Because mud has poor mechanical resistance and is poorly waterproof, the builder usually lays a full length stone wall base prior to a mud brick wall construction. This foundation may be quite small when the wall is built in rocky terrain. Otherwise, compact or masonry stone is used. In some cases, these foundations are extended above ground level, thus becoming an actual wall base. More rarely, this type of wall is added to hewn-stone masonry, overlapping the stone base. Building materials Type and hardness : The raw material used is more or less clayey earth, in association with variable proportions of sand, chopped straw, gravel, stone or clay. On the common scale fixed for this study (1=chalk 10=granite ), the hardness of mud brick is reported as weak (1 to 3), and rarely average(4-5). As this material is man made and not found in nature, its mechanical qualities directly depend on the quality of: available earth, possible aggregates and brick-making process. Mud bricks are even harder when the earth used is clayey. When chopped straw is added, the fermentation process produces lactic acid increasing the material s resistance. Modules : The modules are limited in volume. The average length of mud bricks made in the Mediterranean area vary from cm, height from 5-33 centimeters, depth from centimeters. The average volume thus ranges from 1,5 DM 3 (Spain) to 16 DM 3 (Jordan). The regularity of the volumes in a same series depends on whether they are made using a mould or not. Because bricks are handmade and produced locally, modules may vary considerably inside the same country and the same series. Size may also vary between modules of the same production. Construction principle : stone basement Mortar laying Realisation / Construction: This technique is used for the building of one-face walls or two linked facing walls. It is only exceptionally found for two non-linked facing walls. Mud bricks are always laid in mortar. The mortar used is made of earth and various aggregates in variable quantities ( more often : straw, sand, gravel ). The aggregates used depend on the availability of raw material on the building site. Binding materials : For all the countries studied, earth is used as binding material. It is sometimes combined with lime (in Greece, Palestine, Portugal, Turkey). Aggregate : The aggregates and framework used are sand, gravel, chopped straw, organic fibers, in different combinations depending on local availability. Aggregate-grading : The granularity of these aggregates depends on their kind and varies from 0-3 to 0-21 millimeters. Dose ratio : The compositions vary from one place to another, sometimes privileging binding materials, and other times aggregates. When lime is used in the composition, it s dose is irrelevant. Construction principle : dimensions 2/6

3 CONSTRUCTION PRINCIPLE (CONTINUED) Thickness and Dimensions The thickness of walls made of mud brick ranges from 40 cm minimum to 60 cm maximum. In some rare cases, in certain countries, mud brick walls are 30 cm minimum, sometimes even exceptionally 20 cm, and up to 80 cm maximum. Such walls are usually limited in height, and in most cases are used for one floor only when wall thickness is under 30 cm. Nonetheless, it is possible to build walls up to a maximum height of 8-10 m high, on a wall base of an average 50 cm thick. Finishing Mud brick doesn t resist atmospheric weathering well, and is very sensitive to humidity. Protecting this type of wall is therefore essential to withstand ageing : coating or rendering are reported in all the countries studied. The protecting materials are a rendering of earth or lime, or an earth coating covered with lime-wash. The composition of the finishing coating can vary. We find all the raw materials used in making brick: straw, gravel Bare walls are scarce, and only reported for annex buildings or surrounding walls. Tools No specific tools have been reported by mud brick wall builders: traditional masonry tools are the only ones reported. For brick making however, the use of moulds enables the making of a series of homogeneous modules. Tools to level the bricks are sometimes used to squeeze and tighten the earth in the moulds. Extracting the earth is simply made with common tools: shovels, picks. Trades In all the countries of the Mediterranean area, it is the mason who makes and lays mud brick. In rural areas, this technique is even sometimes implemented by the users themselves. In certain countries, the mason gets his material from a brick maker. Thermal and Acoustic Performance The thermal performance of mud bricks generally ranges from good to very good in the countries of the Mediterranean area. A mud brick wall s main quality is in the regulation of inside temperature, in a climate subject to great variations in temperature. A mud brick construction is built with great attention to the thickness and mass of the wall thus giving it high thermal qualities. This type of wall slows the penetration of heat during the day and retrocedes it usefully during the night. The acoustic performances, ranging from fair to very good, vary according to the density of the raw materials used. Construction principle : Tools and modules Ageing pathology Linked to materials and climate conditions : The encountered pathology is directly linked to the high solubility of mud. Good maintenance of the outside coating is essential. When the coating deteriorates, mud masonry is directly exposed to the damage of rain waters, which leads to a quick deterioration of the pointing followed by crumbling of the bricks themselves. Construction principle : realisation Linked to techniques : Generally speaking, no specific pathology linked to this technique has been reported. However, the quality of this kind of masonry depends on the attention brought to the making and laying of the modules. Ageing pathology 3/6

4 CONSTRUCTION PRINCIPLE (CONTINUED) REALIZATION DESCRIPTION Example in Algeria: - The building of the wall always takes place in the good season: between May and October. You must make sure there is no rain and enough sun to dry the earth. The work is carried out by an unskilled or little skilled mason, helped by two workmen who hand him the bricks and the mortar. - There are two phases in building a wall: first preparation, when materials are made, and secondly the building when the materials are laid and adjusted. Quite a few workers can cooperate in the construction, supervised by the mason. - You must sort out the clay to rid it of impurities. This earth is kneaded with the feet, rhythmically, and sprinkled with water. Chopped straw can be added, as well as gravel and sand pumice stone debris (tafza) to increase resistance and reduce shrinking. - Let the mixture impregnate and ferment for 24 hours maximum: fermenting produces lactic acid that makes the brick more resistant and less pervious. While fermenting, straw mixes better with the earth, ensuring the brick high homogeneous qualities. - First, mould and shape the mortar in flat baskets, woven straw baskets, palm leaf moulds or wooden moulds. Level and smooth the bricks' surface with a little water, using the palms of your hands. Remove from the mould the following afternoon. - Let the lumps of toub dry in the sun for ten to fifteen days, turning them around after three days. - Once the materials are sized and made, the mason starts tracing the foundation. He traditionally measures in cubit, but often uses the meter, the metric system having become common today. To lay out the foundation area, he uses stakes of wood, that he drives into the ground at the four corners. These stakes are taught with woven string made of diss ( a perennial grass in Tell). He digs a shallow furrow, using a pick. The mason, helped by five or six workmen, digs trenches uniform in size, and the same size as the walls to be built. The work is always started in the corners, the time needed varies depending on the depth of the trench (0.50 to 0.80). It often takes a few days. - Fill in the trench foundation with big stones or blocks of antique stones (site of Mila). The mortar is made with the same earth that was used to make the lumps of toub. - The walls are built without interruption: this base sometimes extends in a wall base about m high, to reduce the risk of crumbling at the bottom. The mason takes the bricks that the workmen hands over to him, and lays them on a bed of mortar using a trowel, a plumb line, a piece of pipe and a wooden ruler to check the vertical and horizontal qualities of the wall. - Build the wall in two thicknesses of brick, laid side by side. Fill in the gaps between them with the same type of mortar. - Three people are required to build the wall: the mason, who lays the bricks, a workman who mixes and prepares the mortar, and a workman who carries the bricks to the mason. The works take from one to two weeks. - The time needed for the wall to dry before laying a floor varies from five to fifteen days depending on the type of mortar used. - The walls can be rendered with clay, cow dung mixed with finely chopped straw. Wall protection can be strengthened by a finishing coating made with white earth (temlithit). - Fill in the trench foundation with big stones or blocks of antique stones (site of Mila). The mortar is made with the same earth that was used to make the lumps of toub. - The walls are built without interruption: this base sometimes extends in a wall base about m high, to reduce the risk of crumbling at the bottom. The mason takes the bricks that the workmen hands over to him, and lays them on a bed of mortar using a trowel, a plumb line, a piece of pipe and a wooden ruler to check the vertical and horizontal qualities of the wall. - Build the wall in two thicknesses of brick, laid side by side. Fill in the gaps between them with the same type of mortar. - Three people are required to build the wall: the mason, who lays the bricks, a workman who mixes and prepares the mortar, and a workman who carries the bricks to the mason. The works take from one to two weeks. - The time needed for the wall to dry before laying a floor varies from five to fifteen days depending on the type of mortar used. - The walls can be rendered with clay, cow dung mixed with finely chopped straw. Wall protection can be strengthened by a finishing coating made with white earth (temlithit). 4/6

5 ASSOCIATED WORKS Angles and Columns Angles : Possible treatment in the technique, using the same materials No specific processing of angles has been reported. Angles are harped (toothed), the same elements as for the facing are used. Columns : Possible treatment in the technique, using the same materials Columns are most often impossible to build with mud brick. The low mechanical resistance of mud brick does not allow it to withstand heavy local loads. Windows and Openings Lintels and Arches: A one piece wooden lintel is the most commonly found lintel for mud brick constructions throughout countries of the Mediterranean area. The number of pieces of wood can change depending on the type of wood available and the thickness of the wall. Exceptionally, brick lintels, with or without relief arches, are used to make openings. Angles and colunms Jambs: Jambs are not processed in any specific way. They are often built in the wall itself, in the same material and using the same technique. Jambs are toothed. In some cases, full wooden frames have been reported. A frame combines a lintel, jambs and supports integrated in a single element: the frame is built in the wall during construction. Supports: Non protruding supports are used for openings in mud brick walls throughout the countries of the Mediterranean area. Dimensions: Mud brick walls do not allow for large openings or windows. When these openings are only for ventilation, they are usually of very small size, (length:15 cm, height: 20 cm). The maximum dimensions generally reported for doors are: (width:100 to 127 cm height: 210 to 300cm ). Associated Elements Generally speaking, no specific associated elements have been reported for this kind of wall in the Mediterranean area. Wall-roof Connections No specific processing has been found for wall-roof connections. However, to protect the wall, the roof usually has an overhang, variable in size, on the eaves, and sometimes on gables for sloping roofs. No specific connecting elements have been reported. The structure of the roof usually sits directly on the mud brick wall. Windows and openings 5/6

6 USE, EVOLUTION AND TRANSFORMATION Use Types of building: In most of the studied countries, mud brick are used for housing. This technique has seldom been reported for the construction of public buildings, either official or religious. In most countries it is usually considered as a means of construction for humble houses. The wide availability of materials and their low cost, combined with the rudimentary technical background needed, make this means of construction well within reach of the users themselves. Period when the technique first appeared. Period when the technique is in use still used today or disappeared : Throughout all the studied countries this technique has been reported as extremely ancient. Its use is so far back in time that it can t actually be dated. The use of mud brick has disappeared in most studied countries. This technique was still in use until the middle of the 20th century. Reasons why the technique disappeared or has been modified : The reason that explains the disappearing of this technique is the emergence of new, more performing materials. The constraints in the preparation, protection and upkeep of mud brick walls and renderings generally explain why modern, easy-to-use materials were preferred to traditional brick masonry. In some cases, social and economic changes (industrialization, economic growth of the population) explain why this technique disappeared. The users gradually profited from an easy access to substitution materials (concrete blocks, terracotta) Evolution / Transformation Materials: Mud generally remains confined in the poorest and the most isolated areas, or in the areas most associated to this technique for the repair/restoration of prestigious buildings. The use of mud is gradually being replaced by hollow bricks or concrete breeze blocks bound with cement mortar, all products which are easily available on the market. With these new techniques, the wall built in this form barely stands as a filling-in associated with a bearing structure made of reinforced concrete (posts-beams structure). The hollow bricks or the manufacturated concrete breeze blocks are not equaling mud from the point of view of their mechanical and physico-chemical features. On the other hand, soliditywise, bricks and concrete breeze blocks are more resistant and long-lasting than mud, especially when facing streaming rainwater. Technical aspects: The actual wall is most often built between the bearing points of the reinforced concrete structure, as a two linked facing wall for hollow bricks, and as a single face wall for the breeze blocks. The contemporary joints in cement mortar are usually much thinner than the ones in earth mortar. Evaluating materials and replacement techniques: On a strictly economical plan and due to the fastness of production, the use of hollow bricks or breeze blocks is satisfactory. Nevertheless, the use of this replacing technique is not conclusive when regarding thermal comfort. From the physico-chemical point of view, the reinforced concrete frame suffers from major dilatation phenomena under great changes in temperature, and therefore generates craks in contact areas between the filling masonry and the bearing structures in reinforced concrete (post-beam). From an aesthetic point of view, this replacing technique is not convenient for old structures. In addition, these two structures are not mechanically compatible. These new techniques are mainly employed on new constructions. 6/6