D5 Sloped mechanical (flat) tile roofing

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1 Building techniques : Country : D5 Sloped mechanical (flat) tile roofing Mediterranean Area PRÉSENTATION Geographical Influence Definition Sloped mechanical (flat) tile roofing - Roof with common slope from 25% to 40% covered with flat industrial tiles, laid with mortar, assembled by interlocking, nailed or fixed on a wooden lathing. - The tiles of terracotta clay, constant red colour and rectangular shape, are a common length of 40cm, and a width of 20cm to 30cm. - The roofing generally rests on a wooden frame, stacked or assembled, or sometimes on a vault. - This technique developed starting in the middle of the XIXth century with the rise of industrial production, the tile of Marseille was exported to many countries. While in certain countries the use of the mechanical flat tile decreased after the Second World War, this material still remains widely used throughout the MEDA area. Environment In the MEDA area, sloped flat mechanical tile roofings are generally present in urban and rural environment, sea side, plain or mountain, except Israel where they are found neither in rural nor mountain environment, and in Portugal where they are not in mountain areas. This type of roofing is common in all countries. General view : Detail close-up : 1/5

2 CONSTRUCTION PRINCIPLE Materials Nature and Availability (in what form) The roofing consists of an assembly of mechanical flat tiles, manufactured industrially with homogeneous clay. After mixing, pressing or moulding and drying of clay, the tiles are fired at a regular temperature of 1000 C to 1200 C, which gives them a uniform bright red colour. If the first mechanical flat tiles were produced in France, in Altkirch (Alsace), it is in Marseilles that their industrial production rose, starting from the middle of the XIXth century. The tiles of Marseilles were exported massively towards the five continents till the Second World War, which explains why many countries of the Mediterranean imported them, before producing them locally. Contrary to many countries ( Egypt, Spain France), this material is not regarded as a component of traditional architecture in the three Maghreb ( North Africa) countries (Algeria, Morocco, Tunisia), where the mechanical flat tile represents the architecture of the industrial era or the colonial period. Modules, Dimensions, Thickness, Dosages Mechanical flat tiles, rectangular shape, are a common length of 40 cm, and a common width of 20cm to 30cm; their height varies 1,5cm to 5cm. A unit weight is between 3 kg and 3,5kg, for an average weight of 35kg to 40kg per m2 of roofing. The name of the manufacturer and the place of production are generally registered on the mould. The total common thickness of the roofing is between 15cm and 30cm. Type of laying Type of laying Mechanical flat tiles are generally encased, nailed, or fixed with a wire (to avoid tearing with the wind) on a lathing or wooden boards, or sometimes, sealed with mortar. Associated framework The roofing with flat mechanical tiles generally rests on a wooden frame, stacked or assembled, or sometimes on a vault. Drainage Adapted slope (%) The slope varies from 20% to 91%; the common slope ranges between 25% and 40%. The flat mechanical tile roofings enable stronger slopes than roman (curved) tiles. Wind tearing exposure is lessened when the slope is weak; a slower runoff can cause infiltration. Water collecting and drainage Rainwater is more and more often collected by gutters, particularly in urban environment. They are generally drawn away from façades by overhanging eaves (projecting roof). Processing of specific points (bargeboards, runoff, neck gutters, ridge sheathing...) In certain cases, the same accessories are used for the processing of specific works: ridge tiles, bargeboard or ventilation, parts of the sewer for the neck gutters, chimney stocks... The ridge tiles are sometimes V shaped, and reversed to allow for ventilation. Half-tiles, less wide, make it possible to limit cutting. Construction principle: materials and type of laying general view and details 2/5

3 CONSTRUCTION PRINCIPLE (CONTINUED) Tools No specific tool is necessary for flat mechanical tile roofings. Trades Trade, Number of people necessary According to cases, flat mechanical tile roofing is carried out by a mason or a roofer, sometimes helped by a carpenter. Two to five people at least are necessary to carry out this work. Performances Waterproofing, Protection against bad weather The resistance of flat mechanical tile roofing is generally good, against rain, snow and wind, the material provides good tolerance to strain. The industrial and homogeneous firing guarantees good mechanical resistance of the tiles. The lightness of this type of roofing limits frame overloads and sag, which can cause a deformation of the roof, and water infiltration. Thermal insulation Although terracotta clay is a good thermal insulator, the thermal performance of flat mechanical tile roofing depends mainly on the quality of the support. The laying of dry tiles allows for good ventilation of the roof. Ageing pathology Linked to materials and climatic conditions : The infiltration of rainwater can be caused by capillarity or bad flow, or by defective joints or tiles. Various lichens or organic elements can prevent good water run-off. Relatively thin and often cracked after a few decades (low impact resistance, frost splitting, lichen...), old tiles do not always ensure the waterproofing of the roof. Linked to the technique : Too weak a slope of roof,or obstruction of gutters can cause infiltration by capillarity. A degradation of the frame (sag, deterioration of wood...) can cause water infiltration. Construction principle : treatment of particular points, drainage cornices, eaves, side bargeboards 3/5

4 CONSTRUCTION PRINCIPLE (CONTINUED) REALIZATION DESCRIPTION Conditions of realization : The realization of work must be done in dry weather, to avoid rainwater infiltration; no particular protection is necessary, except in Israel. Preliminary works : A horizontal lathing is fixed on the frame, the spacing corresponds to the length of the tiles, while paying attention to cutting, sometimes necessary on the top row. The support and the jutting out of the roof (eaves, cornice...), as well as the system to collect water (gutters and gutters), are implemented before the roofing. Before laying, the state of each tile must be checked: the tile is cracked if it does not make a clear sound; a tile must withstand the weight of a man without breaking. Realization : A first horizontal row of tiles is laid temporarily against the sewer, to prevent the need for small bands of cut tiles against the bargeboard if the roof is on a orthogonal plan. After determining a final laying position to avoid difficult cutting; and if you cannot avoid cutting, the left hand bargeboard is prepared with half-tiles, before the laying of the tiles by successive horizontal rows, laid upwards. Each roof slope is processed successively; on the other hand, the lower horizontal rows (with the sewer) must be laid first. When the slopes of the roof are covered, the ridge tiles are laid on ridge sheathings and on all hip rafters. Significant details : The cutting of the tiles for chimney stocks or lanterns must be relatively accurate, to avoid excessively broad joints of mortar. The ridge tiles must be covered opposite dominant winds. Means of verification : One can check the waterproofing of the roofing by sprinkling water, to detect possible water infiltration. 4/5

5 USE, EVOLUTION AND TRANSFORMATION Use Types of buildings Flat mechanical tile roofing is on all types of buildings throughout the MEDA area. Period when the technique first appeared / Period of use of the technique - contemporary or disappeared. Flat mechanical tile roofing appeared in the middle of the XIXth century, with the industrial production of this material which initially developed in Marseilles, then in many countries. Use spread quickly, then gradually declined after the Second World War; this technique is still used today. Reasons of the disappearing or the modification of the technique No object. This technique is still in use today. Evolution / Transformation The materials Terracotta mechanical flat tiles are sometimes replaced by less expensive concrete tiles, but thermal performances are poor. Sometimes Roman curved industrial tiles replace flat tiles. The technical aspects If mechanical flat tiles are still used, technique of laying sometimes evolved towards more efficient systems. Evaluation of materials and replacement techniques The new faster laying techniques of mechanical flat tiles, are satisfactory; they are also used in new building. 5/5