building c6 – barrel vault - rehabimed para el mantenimiento y rehabilitacion de...c6 syria –...

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 1/6

PRÉSENTATION

Geographical Inf luence

Definit ion

Barrel vault

- Horizontal framework, semi-cylindrical shape resting on load-bearing walls - For the building, use or not of a formwork or formwork supports. - Used as passage way or as roofing (in this case, the extrados is protected by a rendering).

Environment

One finds the barrel vault in the majority of the Mediterranean countries studied. This structure is usually used in all types of environment: urban, rural, plain, mountain or seaside. Associated floors: Barrel vaults are used for basement, intermediary and ground floors for buildings and public structures. This technique is sometimes used for construction of different floors. In Syria, the barrel vault is found in urban and rural environments. It is common in all types of environments except mountainous areas. Associated floors: In Syria, this technique of construction is used in house cellars and basements, it is also found on ground floors in the shops, workshops and in old souks.

I l lustrations

General view: Detail close-up:

Building techniques :

Country :

C6 – Barrel vault

Syria

C6 Syria – Barrel vault


CONSTRUCTION PRINCIPLE

Materials

Nature and availability (shape in which it is found) For the construction of barrel vaults, the most often used materials are limestone and terracotta brick in all the studied countries. Other kinds of stones are also used according to the local availability in materials ( schist and granite...). The materials added for the filling of the interstices of the extrados, or for the composition of mortars are: broken brick, lime, gypsum plaster, gravel or pieces of broken pots and coal debris. In Syria, the stone is the principal material to make barrel vaults. It is used in two shapes: either well cut and dressed to produce a smooth and orderly intrados, or rough stones which produce an irregular intrados called “Gamce” locally. The barrel vault is laid in mortar masonry; the filling material is made up primarily of earth. Modules, Dimensions, Dose ratio The barrel vault is masonry laid in mortar: the modules are assembled one against the other according to a sloped plane determined by a radiant wire that shows the angle of each section from the bottom of the vault to the key, and from the center of the arc. The stone or brick modules which make up the vault can be cut so as to form a specific key for the vault (2 tilted faces make up both a stone course and a bearing surface). They are often hardly outlined in flat stone: mortar catches up any irregularities showing on the surface. In Syria, the barrel vault is assembled with stones, sloped on a curve drawn by a fixed wire, determining a ray up to the arch key. The dimensions of the stones of the cross vault are approximately 35X30X25 cm and the thickness of the vault is 35-40 cm. In addition, the semi cylinder arch of the vault can vary in shape and dimension. The vault can take on several shapes: half-circle, Persian arch or horseshoe, depending on the positioning of the centre of the arch or by drawing multiple arch centres. As for the dose ratio, the mortar used is made of 70% earth and 30% of straw, sometimes earth and lime.

Type of laying

Type of laying, use of a formwork, formwork supports The building of the vault is generally carried out using a wooden formwork. The latter is composed of at least two trusses (section of the vault), on which one fixes laths of wood (sole-piece), the outside shapes the intrados of the vault. The formwork can also produce a more approximate shape, which is then corrected with a bed of earth or sand... Anchored directly in the walls (cross beam, retractable) or supported by bolders (projecting stones left in place after laying ), this unit constituting " the formwork " is held by supports. The laying of stones and bricks is made from the springer to the key by balancing the loads on both sides of the vault axis. In the Mediterranean area, some techniques are freed from this formwork system (low wood supplies? tools are considered as overly cumbersome?, particular and local know-how?...). Building without formworks is possible with regular shaped modules (terracotta brick, cut or not), well prepared mortars (adherence of bricks, hardening speed...) and with a particular laying method. The latter seeks to limit the overhang of a key stacking, by creating intermediary support joints, by slanting the laying axis (springer/key/crown) towards the walls. In Syria today, barrel vault is laid with a wooden formwork. The main formwork is semi-cylindrical, assembled lengthwise between two load-bearing walls, supported by horizontal wooden boards and by vertical beams which carry the framework, taking on the shape of the vault; the vault is constituted on top of this unit.

Trades

Trades, number of people necessary The barrel vault is exclusively carried out by experts, mason, mason/stone cutter, or stone cutter helped by assistants (significant handling, mortar to prepare...), and sometimes assisted by a carpenter for the realization of the formwork. In Syria, Several people of art are needed to make a barrel vault. Initially, a mason and mason/stone-cutter are needed, along with several common masons to handle and prepare the mortar and filling. Sometimes, it would be necessary to call upon a carpenter to make the formwork.

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Construction principle: perspectives, diagrams

Construction principle: type of laying, general view and detail close-up



CONSTRUCTION PRINCIPLE (CONTINUED)

Tools

In addition to traditional mason tools, no particular tool is necessary for the building of the vault in throughout the studied countries. In Syria, the traditional tools of the mason used to make cross vaults are: 1. Hammers in several shapes. 2. Chisel. 3. Hammer with transverse edges: to shape and dress stones. 4. A trowel to spread the mortar.

Performances

Physical (span...). This construction technique leads to span widths that range from 1 to 7 meters, for a thickness that varies from 30 to 50 centimeters and can even reach 1 meter on the edges of the vault in Tunisia. In Syria, the span of barrel vaults varies considerably according to the type of construction and the shape of the arch, but the most important point is to keep certain proportions between the length, width and height. The span can be between 2 and 4 meters in houses and reach up to 6 meters in old souks. The thickness of the walls varies according to the shape of the arch; the thickness of the vault is approximately 40 cm. Thermal - Acoustic. For a stone construction, limestone in particular, the thermal and acoustic performances have been reported from rather good to excellent by all the countries concerned. Considering the significant mass of the vault, its thickness, the materials used in its construction, this piece of work has remarkable thermal and acoustic insulation qualities. In Syria, the thickness of this stone roofing allows good performance, the earth and mortar filling is thick and ensures both thermal and acoustic insulation.

I l lustrations

Tools

Construction principle: performances.



ASPECT, PATHOLOGY

Aspect

Finishing, associated roofing. The intrados of the vault is generally covered with a rendering. However, in the case of ashlar vaults or carefully laid bricks, the facing can be left bare. In the case of a vault for a passage way, the extrados of the vault generally does not get any particular processing; haunches are frequently filled with various materials (quarry rubble, building site residue), the unit gets a system to seal the ground. In the case of a roofing vault, the extrados of the vault has regular lines, and receives an elaborate waterproofing rendering. In Syria, after the completion of the barrel vault one fills the gaps between the stones shaping the vault, to a thin and smooth mortar is spread on the extrados. As for the intrados, the slope is shaped with two layers of lime rendering: - the first called locally "le cloue" is made up of 50% earth and ashes plus 50% limestone and left to rest for 3 days before use. - the second is a smooth rendering: 2/3 lime plus 1/3 hemp, stone powder and soap, left to rest for 5 days before use.

Ageing pathology

Linked to materials and climatic conditions : As for stone or brick masonry, pathologies related to materials originate in water (capillarity, infiltration, condensation...), which dissolves the mortars and weakens them. The control of water infiltration is more significant in the case of the vaults; Beyond the dissolution of the mortars it is necessary to note direct erosion, that can affect the rendering mortars. In Syria, barrel vaults are affected by the climate and moisture which deteriorate and then damage the external rendering of the vault. It is necessary to carry out repairs with rendering before the climate affects the stones, and causes any partial damage to the vault. Linked to the technique: The vaults produce lateral thrusts, that are weak in the case of the barrel vault. However, not taking this strain into account in dimensioning load bearing walls leads to a cracking of the vaults, sometimes even collapse. In Syria, no ageing pathology linked specifically to the vault technique of was reported; it is however necessary to check the thickness of load-bearing walls because of lateral thrusts that can cause collapse.

ASSOCIATED WORKS

Openings

Small openings can be made to ventilate the rooms (in Palestine and Israel) or to give light, particularly in the souks (Tunisia). The rectangular openings are between 0,5 and 1 meter. A peripheral frame (rafter) distribute the loads. In Syria, barrel vaults can have high openings in particular cases, e.g. in a covered souk, but not in houses. These openings are square or rectangular, distributed lengthwise, contributing to ventilation and lighting.

Connection framework - Vert ical Structure (wal l ) :

No type of connection was reported: the vault is assembled in the continuity of the walls, at the same time and by the same people. The two works are indissociable. In Syria, on the last top row of load-bearing walls and beginning the vault, one lays stones called "main stones" which overhang approximately 2 cm and carry the other superimposed stones which constitute this vault.

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Ageing pathology: linked to materials and to climatic conditions.

Associated works : connection framework - vertical structure (wall)



REALISATION DESCRIPTION In Syria : (Text in French) Les voûtes en berceau sont posées au moyen d'un coffrage en bois construit au préalable sur la longueur ou une partie de la voûte, il vient s'appuyer sur deux murs porteurs. Le coffrage en bois est élevé en deux étapes : tout d'abord, des planchers en bois sont montés horizontalement et fixés sur les murs porteurs supportant ainsi des piliers en bois qui portent le coffrage semi cylindrique qui prend la forme de la voûte en question. Le procédé est complété par la superposition des pierres qu'elles soient taillées ou brutes avec des dimensions de 35x30x25 environ, ces pierres sont superposées au fur et à mesure que se dessine le profil de la voûte en utilisant le mortier comme liant. On commence la construction de la voûte par les deux côtés des murs porteurs en posant une rangée en saillie, puis en montant la paroi avec son profil pour arriver jusqu'à sa clé. En cas d'utilisation des moellons, les vides sont comblés par de la terre, des petites pierres et du mortier pour avoir une surface lisse. Le tout est couvert par une autre couche de terre d'épaisseur entre 50 et 70 cm, formant ainsi le plancher de l'étage du dessus. En cas d'utilisation des moellons, l'intrados de la voûte est revêtu par un enduit de chaux sur trois couches : deux rugueuses "Cloue et Btaneh" et une lisse "Dhara".



USE, EVOLUTION AND TRANSFORMATION

Use

Types of buildings This framework is used for all types of construction : housing, monuments and buildings public, facilities (mosques, souks, hammam, trade, craft industries, caravanserais) In Syria, barrel vaults are used in all types of buildings in old cities for long shaped constructions, they are also used for the roofing of passageways, alleys, Iwans in houses and finally in old souks. Period when the technique first appeared. Period when the technique is in use – still used today or disappeared : This construction technique has existed since antiquity. It is on the verge of disappearing everywhere, when it hasn’t already completely disappeared. It is used, however, in the restoration of certain buildings. In Syria, the oldest constructions using this technique in old cities go back to the Byzantine period. This technique remained in use till the end of the 19thcentury. The oldest examples are in old cities and go back to the 10

t h century. Nowadays, the use of barrel vaults is maintained and limited to restoration and restoration campaigns. Reasons why the technique disappeared or has been modified : The reasons evoked by all the countries are mainly; high cost, slowness of work and skilled labour required for the technique, and a loss of know-how related to this technique. In Syria, the emergence of new construction techniques, like reinforced concrete for roofing, together with relatively high cost and lack of specialized labour have led to a disappearing of this technique in new constructions.

Evolut ion / Transformation

The materials The stone barrel vault with lime mortar is used only for rare works of restoration. It has been replaced by hollow floors, using reinforced concrete girders, soldered trellis, cement. All these new replacement materials replace, on the commercial market, the traditional materials used in the construction of masonry with mortar. In certain cases, we can consider that it is not completely lost as far as the shape is concerned, and it simply changed because of the emergence of brick, especially hollow brick, that generalised and replaced stone. In Syria, there is no major change in the materials used for barrel vaults. On the other hand, cement has replaced lime or earth in the composition of the mortar used as binding material. The technical aspects The hollow bodied floor is the covering system that replaces the barrel vault. The barrel vault is built as a whole with the load bearing wall, without interruption, whereas new floors are built with reinforced concrete beams that are not embedded in the walls: they thus constitute mere filling walls, made with hollow bricks, and do not play any structural role. It is therefore recommended to embed the beams using pins, and sink the steel elements in an uninterrupted reinforced concrete blanket over the whole floor frame. In Syria, the proportions of materials are the same but only for restoration. The same old tools are still used for the construction or restoration of barrel vaults to obtain the same aspect. There is nonetheless an evolution: the stones used are machine cut and shaped in a factory rather than on the site. Evaluation of materials and replacement techniques - On an economic level and given the speed of production, the use of reinforced concrete beams is amply satisfactory - Reinforced concrete beams undergo rather significant strain under the effect of temperature variation - Replacement materials are more vulnerable to water infiltration, and less resistant in time - On an aesthetic level, the aspect of finishing of contemporary reinforced concrete vaults is completely different from traditional crossed vault in stone or brick. - Mechanically, the reinforced concrete floor framework undergoes traction, which is not compatible with the bearing structures in masonry which undergo compression: cracks appear at the contact point of the two structures . In Syria: - The use of cement mortar instead of lime is faster, thus more profitable on an economic level, and time saving. - Replacement materials are more resistant to water infiltration.

building c6 – barrel vault - rehabimed para el mantenimiento y rehabilitacion de...c6 syria –...

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