ROOF COVERING MATERIALS | TYPES OF ROOF COVERING MATERIALS | ROOFING MATERIALS

ROOF COVERING MATERIALS

Roof covering material provides protection to the roof and the structure. It prevents rainwater, moisture, heat, dust, etc. from entering the building from the top. The roof covering does not share the load in the building. It is rigidly fixed to the roofing structure with various types of fittings and fixtures. The various types of roof covering materials used include the following.

 

Thatch covering

This form of covering is extensively used in sheds, low-cost houses and village buildings. It is considered suitable for rural areas because it forms the cheapest and the lightest material as a roof covering.

The framework for supporting the thatch consists of round bamboo rafters spaced at 30 cm and tied with split bamboos or bamboo reapers laid at right angles to the rafters. The thatch is tightly secured to the framework or battens with the help of ropes or twines dipped in tar. Sometimes fire-resisting properties are imparted to the thatch by soaking it in specially prepared fire-resisting solutions that are very costly. For adequate drainage of rainwater, the thatch covering should be at least 15 cm thick and laid with a slope of 45°.

 

Shingles

The use of wood shingles as a roof covering is generally restricted to hilly areas where wood is easily and cheaply available in abundance. Wood shingles are nothing but the sawn or split thin pieces of wood resembling slates or tiles. These sawn shingles, which are obtained from well-seasoned timber, are dipped in creosote to impart preservative qualities. Shingle strips are driven on rafters and shingles are nailed on their top. Shingles are commonly obtained in length varying from 30 to 50 cm and in width varying from 5 to 25 cm.

 

Tiles

The use of tiles is one of the oldest methods of roof covering. The tiles are named according to their shape and pattern and they are manufactured in a similar manner as bricks. The clay tiles are of various types such as flat tiles, pantiles, pot tiles or half-round country tiles and patent tiles such as Mangalore and Allahabad tiles. Sometimes cement concrete tiles are also used but are limited on account of high cost and the difficulties in their manufacture. Clay tiles have been widely used as a roof covering material for residential buildings.

 

 

Advantages of clay tiles as a roof covering

i. Clay tiles, being non-conductors of heat, prevent the building from extreme changes of the temperature outside and keep them cool.

ii. These tiles provide quite a durable roof covering when made of well-burnt good materials.

iii. They are quite strong and pleasing in appearance.

iv. If properly selected and laid they have good resistance against fire and moisture penetration.

v. These tiles provide a very economical roof covering with aesthetic values and hence are used for urban and rural houses.

However, these tiles suffer from the limitation of being heavy in weight. The weight of the roof covering is further increased as the rafters are kept closer to reduce the span of timbers and to throw off the rainwater. The average weight of a tile roof is about 75 kg/m2.

Flat or plain tiles are manufactured in rectangular shapes (size, 25 x 15 cm to 28 x 18 cm) in thickness varying from 9–15 mm. Tiles are not perfectly flat but they have a slight camber usually 5–10 mm. These tiles have two small projecting nibs and two or more nail holes at one end of their surface. These nibs and holes help to fix the tiles on the battens of the roof truss. The tiles should be laid at the proper gauge and overlap both at the sides and edges as it is important for their strength, durability and imperviousness.

Curved pantiles are shorter, less curved, heavier, stronger and more durable than pot tiles. These tiles are moulded flat first and then given the required curvature. These tiles are about 30–35 cm long and are about 20–25 cm wide.

Pot tiles or half-round country tiles are very commonly used for rural houses as they offer a very cheap roof covering. These tiles are laid in pairs of under tiles (concave upwards) and over tiles (convex upwards) with a proper overlap of at least 8 cm on all the sides. The under tiles are flat with a broad head tapering towards the tail while the over tile has a wider tail and a narrower head which is segmental in section. Country tiles are laid in two layers one over the other and the roof is called a doubled-tiled roof. This type of roof requires heavy supporting timbers of greater strength than the usual ones.

Patent tiles are generally rectangular in plan with face corrugations so arranged that the corrugations of tiles fit in or interlock with those of other tiles. These interlocking tiles, which are machine-made, provide a lighter roof covering with a decent appearance. In ordinary works, the groundwork for these tiles consist of battens only. In the superior type of construction, the tiles are laid onboarding covered with a protective coat. Boarding is directly nailed to purlins and tiles are on battens nailed on the boarding.

ALSO READ: What is Roof | Types Of Roof | Pitched Or Sloping Roofs | Flat Roofs | Shell Roofs | Domes

 

Asbestos cement sheets

Asbestos cement is a material that consists of Portland cement and asbestos fibres (about 15 per cent). Roof covering made of this material is cheap, tough, durable, watertight, fire resisting and light in weight. Asbestos does not require any protective coat. Asbestos cement roof coverings are supplied in flat corrugated and ribbed sheets in various sizes.

 

Corrugated GI sheets

These are used for the roof coverings of workshops, factories and temporary sheds. GI sheets are available in various sizes. Generally, 22 gauge sheets are used. End lap of 15 cm and side lap of two corrugations are provided at the time of fixing the GI sheets at the top of the roof. It is light and simple to fix. The only disadvantage with the use of these sheets for roof covering is that during the summer season, the rooms under the roof are heated too much. To protect against the sun, sometimes a layer of ordinary tiles are provided at the top of GI sheeting.

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