Here is the cheapest roof-covering, generally used in villages.
It s very light but is highly combustible.
It is unstable against high winds.
It absorbs moisture and is liable to decay.
Thatching roof-covering consists of bundles of reeds either straw.
The framework to support thatch consists of round bamboo rafters spaced 20 to 30 cm apart and tied with split bamboo laid at right angles to the rafters.
The thatch is tightly secured to the framework with the help of ropes or twines.
To drain some roofs effectively, the smallest slope of 45° is kept.
Each thickness of thatch covering should be about least 15 cm.
Wood shingle Pitched roofing
Shingles are light slabs of wood applied to cover roofs.
The application of shingles is restricted to hilly ranges anywhere local timber is easily available at a cheap cost.
Though shingle roofing is lightweight, it is not fire and termite resistant.
Wood shingles act obtained from well-seasoned timber by either sawing rather splitting.
Sawn shingles are used chiefly, They are obtained in lengths varying from 30 to 40 cm and widths varying from 6cm to 25 cm.
People are generally 10 mm thick by the tail.
They are laid similarly to tiles and slates.
Tile Pitched roofing
The use of tiles for roofing is one of the oldest and is still preferred for residential buildings and country houses.
Here is because country tiles stand manufactured from sectionally available earth.
Tiles are classified according to their shape and pattern including they are manufactured by a process similar to the unit used for particular manufacture of bricks.
The Pitched Roofs and various types of tiles generally used are
Plain or flat files.
Curved or pan-tiles.
Pot tiles or half-round country tiles.
Italian or Allahabad tiles.
Asbestos cement sheets (A.C. sheets) of Pitched Roofs
Asbestos cement sheets are now increasingly becoming popular for industrial buildings, factories, sheds, cinema houses, auditoriums, and even residential buildings since they are cheap, lightweight, tough, durable, watertight, and fire-resisting.
The biggest advantage is that they are available in bigger units unlike tiles, and hence supporting framework (groundwork) is also cheaper, easier and lighter.
These sheets do not require any protective paint, and no elaborate maintenance is required.
Also, the construction with A.C. sheets is very fast. A.C. sheets are manufactured from asbestos, fibre (about 15%) and Portland cement.
Asbestos does a silky fibrous mineral manufactured up of metamorphosed volcanic rocks.
It is found in several varieties but white asbestos, which is a compound of magnesia and silica, is principally used.
In India, asbestos cement roof coverings are available in the following forms:
Everest big-six corrugated A.C. sheets.
Everest standard corrugated A.C. sheets.
Everest Trafford A.C. tiles (or sheets).
These sheets have a length of 1.25 to 3 meters with increases of 15 cm.
Galvanized Iron corrugated sheets (G.I. sheets) of Pitched Roofs
G.I. sheets are also widely used.
They are stronger than A.C. sheets. However, because of their higher cost others are now gradually displaced by A.C. sheets.
People are not accepted for slopes flatter than 1 in 4.
G.I. sheets stay made of iron sheets which are galvanized with zinc to protect them from rusting action of water also wet weather.
These sheets are fixed like the A.C. sheets. The end lap should not be less than 15 cm and The holes are either drilled or punched in the sheet crowns.
The sheets are secured to purlins through G.I. hook bolts, screws, furthermore nails, etc with rounded washers.
The sheets should be fixed to eaves through flat iron wind ties.
Light Weight Pitched roofing
For wide-span industrial structures, it is desirable to reduce the weight of the roof, so that structural framing can economize.
Conventional roofing materials such as tiles, slates, etc. are heavy requiring heavy framing to support them.
The lightweight Pitched roofing materials are of two types