ROOF :A roof is the uppermost part of a building, provided as a structural covering, to protect the building from rain, sun, wind, etc. Roof protects the building from the dam- ages starting from the top.
CLASSIFICATION OF ROOF
●sloping/pitched roof ●Flat roof ●curved or shell roof
SLOPING /PITCHED ROOF
Sloping/Pitched Roof
These roofs are constructed out of wood, steel or combinations of both and the edges of their triangular por- tions are supported by walls. The slope of the roof depends upon the distance between the two supporting walls, type of roof covering material to be used as per the climatic conditions in that locality.
Technical Terms used in Pitched Roof
1. GABLE: The triangular upper part of a wall formed at the end of a pitched roof is known as a gable.
2. HIP: The external angle which is greater than 180° formed at the intersection of two roof slopes is known hipped roof
3. RIDGE: It is the apex line of the sloping roof formed by the intersection of inclined surfaces of roof.
4. RISE: It is the vertical height measured from the lowest to the highest point of a gable.
5. PITCH: The inclination of the sides of a roof to the horizontal is known as pitch. 6. EAVES: Eaves of a roof are the bottom end of a pitched roof. 7. VALLEY: When two roof surfaces meet together and form an internal angle less than 180° it is known as valley.
8. RAFTER: These are the pieces of timber which extend from the eaves to the ridge. 9. PURLIN: The wooden or steel pieces which are placed horizontally to carry the common rafters are known as purlin.
10. BATTENS: These are thin strips of wood which are nailed to the rafters for laying roof materials.
Types of Pitched Roof
1. Single roof
2. Double or Purlin roof
3. Trussed roof
Types of Single Roof
1. Lean-to roof
2. Couple roof
3. Couple closed roof
4. Collar Beam roof
1. LEAN-TO ROOF: Lean to roof is used for verandahs and sheds attached to the main buildings. Its span is limited to 2.5 m. To obtain the required slope, the rafters which alope on one side are secured to wall plates at the upper end and wall plate or post plate at the lower end. The upper wall plate is sup- ported on a corbel and the lower wall plate rests on wall or posts. Wooden battens are fixed onto the rafters to carry the roof cover- ing materials.
2. COUPLE ROOF: These roofs are formed by connecting the two inclined rafters. The roofing material is supported on battens, which are suitably spaced and fixed onto the rafters. This type is suitable for spans up to 3.6 m.
3. COUPLE CLOSED ROOF: This is similar to the couple roof. When the span and intensity of loading are increased, the horizontal thrust developed is likely to push the rafter away. To prevent this ten- dency, the rafters are connected by horizontal members called tie at the bottom as shown in the fig This tie member is used for fixing false ceiling at top. This type of roof is known as couple closed roof and can be used for span up to 4.2m.
4.. COLLAR BEAM ROOF: Collar beam roof is similar to the couple close roof, except that the tie beam is fixed near the middle of the rafters instead of the bottom end. Thistypeof roof is suitable foraspan up to 5.5 m.
Double Roof or Purlin Roof
In this type, an additional member known as purlin is used to support the common rafter at intermediate pointa. If purlins are not used, then dhate point of common after would be uneconomical. To economize the construction purlins are used so that rafters of smaller size can be used.
