Classification of roofs:
Roofs are broadly classified into the following four types roofs:
1. Sloping, pitched or pent roofs
II. Flat or terrace roofs
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The form of construction of root is governed by the plan of a building span, the type of covering material locally available and the architectural appearance required.
The roof covering to be provided should be economical and most suitable according to the nature of the building.
Sloping roofs: The roofs provided with a considerable slope are known sloping pitched or pent roofs. These roofs are suitable where rainfall is heavy and also in snowfall areas.
Different types of roofs are follows:
1. Shed roof: A sloping roof having slope only in one direction is called a shed roof. This is the simplest type of sloping roof and is used for smaller spans.
2. Gable roof: A sloping roof having slope in two directions is called a gable roof. This type of sloping roof is used for larger spans.
3. Hipped roof: A sloping roof having slope in four directions is called hipped or hip roof. This type of sloping roof is mostly used for buildings in hilly areas.
4. Gambrel roof: A sloping roof having slope in two directions with a break in the slope is known as gambrel roof. This type of sloping roof is mostly used for buildings in hilly areas.
5. Mansard roof: A sloping roof having slope in four directions with a break in the slope is known as mansard roof. This type of sloping roof is also used for buildings in hilly areas.
6. Saw-tooth or north-light roof: A sloping roof having glazing fixed on the steep sloping sides of the roof is called saw-tooth or north light roof. In this type of sloping roof, its steep sloping side is kept towards north direction. This type of sloping roof is generally
used in factories where more light is required.
Important technical terms concerning to sloping roofs are as follows:
1. Ridge: The highest point or line of a sloping roof, where the two opposite sloping surfaces meet is known as ridge.
2. Eaves board: A wooden board fixed along the eaves at the end of common rafter is known as eaves board or facia board. Gutter is usually supported at eaves board.
3. Cleats: The piece of timber or angle iron nailed or screwed (for timber), riveted, or welded (for angle-iron) on the trusses, to the support purlins are known as cleats.
4. Battens: The pieces of wood directly nailed to the common rafters are called battens. The roof coverings are directly laid over battens.
5. Purlins: The wooden or steel members laid horizontally to support the common rafters of a sloping roof are called purlins.
6. Barge: The finished edge of a slating or tilting over hanging a gable wall is called barge.
7. Barge board: A wooden board fixed to the ends of the common rafters projecting beyond the gabled end of a sloping roof is called barge board.
8. Pitch: The inclination of the side of a sloping roof to the horizontal surface is called pitch. It is usually expressed as the ratio of the rise to half of the span of the road in degrees.
9. Hip: The line of inter-section of surfaces of a sloping roof forming an external angle exceeding 180°, is known as hip.
Types of Roofs
What are roofs? Classify single roof type of wooden sloping roof?
The covering provided over the top of an enclosure made for a building to keep out the sun, rain, wind, and to protect the interior from exposure to the weather is called as roof.
A roof usually consists of framework provided with a suitable covering at its top.
A good roof is as essential as a safe foundation for a building. Roof must therefore be well designed and constructed to meet the requirements of different climates and covering materials locally available.
Single roofs: The wooden sloping roofs having only common rafters for supporting their coverings are known as single roofs, in these sloping roofs, the upper ends of common rafters and their lower ends are fixed on the walls plates. Single sloping roofs are further
classified into five types as discussed below:
1. Lean-to-roof: This type of sloping roof consists of common rafters which are generally inclined at 30°. One end of each common rafter is placed on wooden wall plates and the other is nailed to wooden post plates laid on top of the posts. Tiles or other roofing materials are placed on the battens having size 40 x 25 mm running across the rafter. It is essential that the leakage at junction between roof and the wall should be prevented.
2. Double lean-to-roof: This type of sloping roof slopes in two direction and is also known as V-roof. It consists of two lean-to-roofs which slope towards each other to form V-shape. At their lower end they are supported on wooden wall plates fixed on a common wall or a number of posts. A gutter is usually fixed at the top level of the common wall or posts to drain off the rain water properly.
3. Couple roof: This type of sloping roof slopes in two directions and is also known as pent or span roof. It consists of a pair of common rafters which are pitched against each other and fixed to the ridge piece. Their lower ends are placed on the wails. A couple roof is not good since it has the tendency to spread at its lower ends.
4. Couple roof ends: This type of sloping roof is modified form of a couple roof. In this roof, rafters are connected by a horizontal beam, known as tie beam, which prevents outward spreading of the roof and also acts as support for any false ceiling to be provided.
5. Collar roof: This type of sloping roof is similar to a couple roof except that the horizontal beam is fixed either at % or 2/3 of the vertical height from the wall to ridge. It is better to place the collar as low as possible for providing maximum lateral strength to the roof.