Building A7 – Mud brick walls para... · A mud brick wall’s main quality is in the regulation of inside temperature, in a climate subject to great variations in temperature. A

This project is financed by the MEDA programme of the European Union. The opinions expressed in the present document do not necessarily reflect the position of the European Union or of its member States. 1/7

PRÉSENTATION

Geographical Inf luence

Definit ion

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. In Syria, this type of wall is widespread in the houses of the old parts of Damascus and its suburbs, as well as in some villages and towns of Northern Syria (Alep, Alsfireh, Tyara). It has been used in this area for centuries as it fulfils most ecological, structural, and architectural needs.

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General views: Detail close-up:

Building techniques :

Country:

A7 – Mud brick walls

Syria

A7 Syria – Mud brick walls


CONSTRUCTION PRINCIP LE

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. In Syria, the type of foundation depends on the nature of the ground of the area: 1. Rocky ground: construction without a real foundation, built from two rows of squared stones laid on the ground. 2. Clayey earth: excavation along the wall zone, 0.50-0.75 m wide, foundations made with stones, two rows or more above ground (50-120 cm), in order to protect the mud brick walls. The height depends on the use of the building and the financial means of the owner. The foundations are built with irregular limestone and lime mortar or " Kasermall ".

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. In Syria, the main construction unit is brick composed of 75 % earth, 20 % straw (corn or barley) and 15 % water. Modules : The modules are limited in volume. The average length of mud bricks made in the Mediterranean area vary from 20–42 cm, height from 5-33 centimeters, depth from 10-36 centimeters. The average volume thus ranges from 1,5 DM3 (Spain) to 16 DM3 (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. In Syria, brick dimensions are 20x40x10 cm, so as to allow the bricks to be laid in both directions, therefore strengthening the connections within the wall (see illustration).

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Construction principle: foundations and basements

Construction principle: axonometries, details



CONSTRUCTION PRINCIPLE (CONTINUED)

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. In Syria, the earth used is fine earth, kneaded with water. Binding materials : For all the countries studied, earth is used as binding material. It is sometimes combined with lime (in Greece, Palestine, Portugal, Turkey). In Syria, nothing specific reported besides Mediterranean commentary. Aggregate : The aggregates and framework used are sand, gravel, chopped straw, organic fibers, in different combinations depending on local availability. In Syria, the reinforcement material is corn straw or barley. Aggregate-grading : The granularity of these aggregates depends on their kind and varies from 0-3 to 0-21 millimeters. In Syria, the mortar used is 1 cm thick for the vertical joints between the brick ones and 2-3 cm between the horizontal rows of bricks. 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. In Syria, 75 % of fine earth and 25 % of water.

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Construction principle: thickness and dimensions.




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. In Syria, the bricks used in the suburbs of Alep are 20x40x10 cm. In Damascus, the bricks can be broader or the same dimensions, but you can also find smaller bricks, 15x15x8 cm called " Sbeiyi " and " Soukkari ", size is related to the type of earth used. The thickness of the brick wall is 65-70 cm: it results from the sum of the length and width of the bricks (see diagram). Height of the walls: 2.55 m. Foundation above ground-level: 40 cm and more.

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. In Syria, on finished masonry, a 2-5 cm thick earth mortar is applied to cover the external façades of the wall. The interior walls are whitewashed with a lime rendering. These layers play a significant role in the resistance, longevity and structural characteristics of the brick 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. In Syria: - a sieve: to sift the earth and obtain fine earth then mixed with water and straw to form a mortar which will cover the external façades - a shovel: to mix the earth and straw -a rubber bucket " Zanbil ": to transport the mortar -a trowel: to mix the earth and straw, and to fill the joints between the brick and rows -a plumb line: to check the balance of the wall -a float: to spread and smooth the mortar at the last stage

Trade s

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. In Syria, the mason is in charge of the whole work. The number of professionals mastering this trade is drastically dropping, and these men of the art have become quite scarce. This mason is traditionally called " Altarrab " (he who strikes the bricks). He is helped by a team of workmen who pour the earth-straw-water mixture into wooden moulds. The production rate of such a team is about 500 units per day.

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Finishing Aspect: preparation (sieving) and construction of renderings. Traditionally, women do this

operation.




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. In Syria, the thickness of the wall (65-70 cm) provides good thermal and acoustic insulation. Mud is a good thermal insulating material in itself. Mud brick walls thus have good thermal qualities: they have great thermal inertia and long delayed temperature action, in addition to porosity which lessen inside moisture.

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 . In Syria,

1. Atmospheric factors and wearing: walls undergo cracking and collapse due to thermal variations and exposure to rain and snow. This causes a deterioration of the surface layers and an emergence of salt and oxide traces, especially when salty water infiltrates the foundations, rises through capillary action and when strain worsens cracks and compression. 2. It is crucial to renew the rendering every year, or every two years at most, if not the external rendering dissolves and allows water and insects to penetrate the inside structure.

Linked to techniques : Generally speaking, adobe bricks badly resist to concentrated local loads or important lateral efforts, due for example to the weight of roofs and floors : diagonal or vertical cracks may appear. However, the quality of this kind of masonry depends mostly on the attention brought to the making and laying of the modules. In Syria, the manufacturing techniques (choice of the earth and drying) help improve the longevity of the building. In the same way, several construction stages play a decisive role for the durability of the building.

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Construction principle: Ageing pathology: linked to materials and to climatic conditions.




REALISATION DESCRIPTION In Syria : (Text in French)

- Tout d’abord on aménage une fosse où l’on mélange la terre et la paille puis on y ajoute de l’eau jusqu’à ce que le mélange prenne consistance.

- On laisse le mélange deux jours en prenant soin de l’agiter (le casser) chaque jour. - Au troisième jour, on prépare le moule en bois (40x40x10 cm) : c’est un moule divisé dans sa longueur en deux parties. - Le mortier de terre est coulé dans les deux parties du moule où chaque partie présente une brique de 20x40x10 cm. - On laisse 5-10 jours jusqu’à séchage complet. - Le mélange de terre pourrait être pétri avec les pieds. - On prépare l’excavation des fondations, puis on élabore les fondations en pierre, ayant 50-75 cm de largeur et une hauteur dépassant

le sol de 40 cm ou plus. - On réalise la maçonnerie avec les briques en terre crue jusqu’à la rangée précédant la coupole. - Arrangement des briques : deux briques en long puis une brique transversale comme fermeture. A la rangée suivante, on inverse la

pose. - Les briques sont liées entre elles par des joints de mortier verticaux de 1 cm d’épaisseur et d’une couche de 2-3 cm entre les rangées

horizontales. - La maçonnerie arrivant à un niveau déterminé (1.5 m), on commence par poser des coussins en bois sur les quatre angles du mur, puis

on avance dans la maçonnerie vers l’intérieur par étapes et vers le haut sur les coins. - Puis les briques avancent de tous les côtés ainsi qu’aux angles pour monter vers le haut en cercle et pour former ainsi la coupole. - On laisse reposer 7 jours après la construction des angles pour séchage avant l’étape suivante. A l’extérieur, au niveau de la jonction

entre le mur et la coupole, on construit le mur en forme d’arc de cercle qui se coupe avec l’œuf « baida », ce qui aide à l’évacuation des eaux pluviales par les côtés.

- Après la maçonnerie, le mortier est posé sur les façades extérieures sous forme de boules. On humidifie et on applique sur toute la surface d’une épaisseur de 2-5 cm. Ainsi, les joints qui permettaient l’infiltration de l’eau seraient couverts.

- On fait de même pour les faces intérieures des murs et, après séchage, on les enduit de chaux qu’on dilue à l’eau, afin de leur donner l’aspect de la peinture (fonction esthétique uniquement).

- Pour préparer l’enduit de chaux, on macère les pierres blanches dans l’eau pendant plusieurs jours, puis on les pétrit pour avoir le liquide blanc.



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. In Syria, in the areas of " Alsfiré " and " Albara " where roofs are cupolas, the angles of the square building are built in the same way, with bricks overlapping each other in the angles. From 150 cm upwards, the angles start to recede towards the inside to bear the cupola. In the area of Damascus, you can find wooden supports in the angles. In the same way, wooden beams can support the wall lengthwise, and at several levels. 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. In Syria, nothing specific reported besides Mediterranean commentary.

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. Columns are more often impossible to build with mud brick. The low mechanical resistance of mud bricks does not allow it to withstand heavy local loads. In Syria, 1. The door: an empty space is left for the door from the first row of construction. When reaching the higher level of the door, a wooden lintel (hard local walnut) is laid in the masonry structure. 2. The window: Simple window: same process as for the door, starting at the level of the support. The lintels can be horizontal or arch shaped, but the latter is growing scarce in the area of Damascus. Very small openings are often made for ventilation: an empty space is left in the masonry, for two or three rows, on a small width. Sometimes hidden inside openings can be made. 3. Interior arches: during the construction of two adjacent cupolas, the interior connecting opening will be topped with an arch and built as follows: the wall are built first, then the bricks are gradually pushed towards the inside, each brick topping the other, up to the key of the arch. Each brick supports the other, all of them interlocking at the top. The width at the beginning of the opening is approximately two bricks. 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. In Syria, nothing specific reported besides Mediterranean commentary. Supports: Non protruding supports are used for openings in mud brick walls throughout the countries of the Mediterranean area. In Syria, nothing specific reported besides Mediterranean commentary. 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 ). In Syria, the door varies according to the house or the room and use: height: 1.7-1.8 m width: 1.2-1.4 m; For the window: 90-120cm; the support is 40-90cm above the course; Small openings: height: 40 cm; width: 20-40 cm.

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Associated works: anchoring with wood angles

Windows and openings - lintels and arches.



ASSOCIATED WORKS (CONTINUED)

Associated Elements

Generally speaking, no specific associated elements have been reported for this kind of wall in the Mediterranean area. In Syria, wooden beams sometimes support the walls.

Wall-roof Connect ions

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 In Syria, in this trade, the concept of the wall-roof connection varies from one area to another. In the areas where the roof is flat, it is often made with wood covered with earth and straw mortar: wooden beams are anchored in the wall to ensure a solid connection. In areas where the roof is a cupola, as in the suburbs of Alep, the outside wall is built in the form of arch and linked with the vault to ensure rain runoff.

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Associated works: wall – roof connections


This project is financed by the MEDA programme of the European Union. The opinions expressed in the present document do not necessarily re flect the position of the European Union or of its member States. 9/9

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. In Syria, mud brick walls are seldom used today, except in the suburbs of Alep (Alsfireh and Tyara). They are also widespread in the area of Damascus. These types of walls are varied and depend on: the nature of earth, the evolution of the trade, and the structural and climatic factors which can affect the raw material. 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.v In Syria, the oldest mud brick works were found in the archaeological hills of " Tall Alsalhié " and " Tall Ghrika " and go back as far as 6500 BC. This technique persisted thanks to the evolution of skills and know-how, reaching a peak in the old buildings of Damascus, towards the end of the Ottoman period. This type of construction was still used in rural areas just a few decades ago, but has no longer been in use for the past twenty years or so. 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) In Syria, this technique of construction is no longer called upon because, according to the inhabitants, it requires too much maintenance, takes up too much surface because of wall thickness, and cannot exceed one floor. Generally, one stopped using this technique because of the emergence of more durable materials, of construction costs as well as social and technical modern changes. Moreover, this technique couldn’t evolve and was been overcome by the emergence of industrial materials which made the work much easier, limiting the development of mud construction.

Evolut ion / 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. In Syria, substitution materials: In the old town of Damascus, cement or terracotta bricks are used, usually for non-structural purposes, generally in wall partitions. They produce low thermal qualities and a poor aesthetic aspect. In rural areas, the inhabitants substituted mud with cement, because manufactured bricks grew scarce, calling upon lost experience and limited to summer campaigns, whereas cement is available at any time. 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. In Syria, the same means and techniques are still used in the countryside. 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. In Syria, the substitution technique changed the distinctive architectural aspect of Damascus, adding poor thermal qualities and aesthetical pollution of the environment.

Documents

Building A7 – Mud brick walls para... · A mud brick wall’s main quality is in the regulation of inside temperature, in a climate subject to great variations in temperature. A