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Types of Pitched Roofs……………..

  1. Single Roofs
  • Lean to Roof (Verendah Roof)
  • Couple Roof
  • Couple Close Roof
  • Collar Beam Roof or Collar Tie Roof
  1. Double or Purlin Roof
  2. Triple Membered or Framed or Trussed Roofs
  • King Post Roof Truss
  • Queen Post Roof Truss
  • Combination of King Post and Queen Post Truss
  • Mansard Roof Truss
  • Truncated Roof Truss
  • Bel-Fast Roof Truss or Latticed Roof Truss
  • Composite Roof Truss
  • Steel Sloping Roof Trusses

 

Single Roofs

  • Consists of only common rafters secured at the ridge and wall plate.
  • Small span where no intermediate support is required for the rafters.

 

Double Roof

  • Here purlins are introduced to support common rafters at intermediate point.
  • Used when span exceeds 5m.

 

Triple Membered or Trussed Roofs

  • Purlin gives intermediate support to the rafters.
  • A trussed roof id provided when:
  1. The span of the room is greater than 5 meters.
  2. When the length of the room is large.

 

Single Roofs- Lean to Roof

  • Simplest type and suitable upto max span of 2.5m.
  • Also known as Pent Roof or Aisle Roof.
  • Wall on one side is higher than the other side.
  • Applicable for sheds, out-houses attached to main building.

 

Couple Roof

  • Formed by pair of rafters which slope to both the sides of the ridge of the roof.
  • Upper ends of rafter nailed to a common ridge and lower ends nailed to the wooden wall plates.
  • Applicable for span upto 3.6m.

 

Couple Close Roof

  • To prevent the rafters from spreading and thrusting out of the wall, the ends of the couple of common rafters and connected by a horizontal member called ‘tie beam’.
  • It may be a wooden member or a steel rod.
  • The connection between wooden tie and feet of rafters is obtained by DOVE TAIL HALVED JOINT.

 

Collar Beam Roof

  • When the span increases or when the load is more, the rafters of the couple close roof have the tendency to bend.
  • This is avoided by raising the tie beam and fixing it at one-third to one-half of the vertical height from wall plate to the ridge. This raised beam is known as the collar beam or collar tie.
  • Suitable for span upto 5m.

 

Collar and Scissors Roof

  • Similar to collar roof.
  • Except that two collar beams crossing each other to have an appearance of scissors is provided.

 

Double or Purlin Roofs

  • These roofs have two basic element- Rafters & Purlins.
  • Purlins gives intermediate support to the rafters which in turn reduces the size of the rafters to the economical range.
  • It is also known as rafter and purlin roof.
  • For larger roofs, two or more purlins may be provided to support each other.

 

Trussed Roofs

  • When the span of the roof exceed 5m and where there are no inside walls to support the purlins then trusses are provided at suitable intervals along the length of the beam.
  • Spacing is limited to 3m for wooden trusses.
  • In this system, the roof consists of 3 elements- Rafters, Purlins & Trusses.

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