Roofing ROOF STRUCTURE MCR Tiles Installation

Manufacturer
Domtec Company Limited
1005/29 Soi Prachachuen 30
Bangsue, Bangkok 10800, Thailand

Tel: 910-1463,910-1465
Fax. (66-2) 910-1465

WHAT IS MCR?

The Micro Concrete Roofing (MCR) technology is a relatively new technology that can be used to produce inexpensive and reliable concrete tiles for roof cover. The tiles are light, durable and can be made by using locally available raw materials: cement, sand and stone-dust.

Figure

ROOF STRUCTURE:

A roof constitutes the most important part of the building. Hence it is inevitable to take special care during the preparation of the roof and its elements. In order to construct a durable roof, not only the covering material must be of a good quality, but also the entire root structure and cover must function as a coherent system adapted to local conditions such as climate, available skill and structural materials. Roof structures are affected by the following factors:

Load: Conventional concrete and clay tiles weigh 50 to 80 kg per square meter whereas the MCR tiles weigh much less. The load of the MCR tiles on the roof structure depends on its thickness. The following Table shows weight factor for specific thickness grades of tiles:

Figure

In addition to the load from the tiles themselves, it is necessary to consider the wind and repair loads, and in some cases the snow load as well, depending on local weather conditions. The most crucial load in most locations is the wind load. Strong winds or storm can cause great damage to a roof if it is not well made and securely fixed to the building. In general a maximum wind speed of 150 km/h is taken into account which is equivalent to a storm capable of uprooting trees. This results in suction forces on the roof of up to 70 kg/ sq.m. The wind can also create pressure of up to 30 kg/sq.m. on the roof.

Slope: The minimum slope required for the MCR tile roofs is 22° in areas with moderate climate and 30 to 40° in areas with severe driving rains. The slope of the roof is also determined by additional criteria such as aesthetic, form and function.

Battens: The setting of battens is the most important part of MCR roofing on which the proper laying of the tiles and water-tightness depend. The spacing of the battens is 40 cm. The battens can be of wood or steel sections which should be able to bear the weight of the tiles and a man (about 80 kg.) for the safety of the workers during construction and maintenance.

Structure: The section and spacing of the purlins and rafters are calculated according to the slope, climate conditions, and weight of the tile. The roof structure needed for MCR roofing is simple and uses light triangular roof trusses. The trusses may be made of wood or metal. But with the increasing scarcity of good quality timber, metal structures are becoming more and more a competitive alternative in roof construction. The main advantage of the metal structure is that it is highly accurate and constitutes an even and stable under-structure for the tiles.

TILE INSTALLATION

To ensure watertightness, a proper installation of the MCR tiles is required, specially in the most exposed areas, that is, the installation of the side and wall plates. The battens supporting the tiles should be fixed by a skilled roofer.

Laying: For the better interlocking of the MCR tiles, they should be first laid from the lower left-hand corner of the slope with the next one overlapping on the top part and then on to form a first vertical row. Then the roofer proceeds with the second and succeeding vertical rows in the same manner. In order to obtain a good interlocking of tiles, it is recommended to install first a complete horizontal row from edge to edge. To align perfectly the columns, it is possible to trace vertical lines with a rope maintained at the top and bottom.

Figure

When the first slope is completed, the second slope is also laid in the same way. The ridge tiles should be installed gradually as soon as enough columns are completed on the second slope. This avoids the need of climbing on the finished part of the roof.

Fastening: For the wind-prone areas, it is very necessary for the tiles to be fastened. In general, all the tiles are fastened by tying the batten with the wire passed through the nib's wire of the tile.

Ridge: The ridge line is covered with specially designed tiles and finally bedded in mortar or pre-casted concrete ridge blocks are glued to allow dry fixing of ridge tiles. Ridge tiles overlap by 50 mm. minimum or may be laid with a double row of ridges.

Figure

Edge: Lateral edges can be made with specially designed tiles; the joint between wall and tiles can be made with a carefully prepared mortar. If there is a roof overhang, a good solution consists in using a fascia board.

Hip and Valley: Hip tiles are specially-designed tiles binded with mortar; valley gutters are most often made of galvanized iron sheet under the cut edge of the tile.

Figure

TRAINING:

Training in the MCR tile production as well as training in installation with the tiles can be provided by the manufacturer. Group training may carried out either at the manufacturer's own training center or at a project site with the equipment provided.

The training costs are established on a case by case basis. For more information and details, please write to the manufacturer.