Single Roof and Double Roof: All you Need to Know

The roof is an important element in the house and serves the basic purpose of the house i.e., providing shelter. The roof is classified into two main types, i.e. flat roof and pitched roof. The pitched roofs are also of two types:

Also Read: Roof & its Classification
  • Single Roof
  • Double Roof

01. Single Roof:

Single Roof is defined as a roof having only a single slope on each side of a central ridge, whereas, in shed roof, it has a single slope, but without a central ridge.

The single roof is a type of sloping roof. In this type of roofs, common rafters are provided on each slope without any intermediate support. Single roof construction is simple than other roofs.

In the single roof, each rafter is supported at two points:

01. At the bottom; on the wall through wall plate

02. At the top; by the ridge

Also Read: Basic Component of a Roof

Single roof has some limitations. Single roof is used for small spans. If greater spans are used, then larger roof sections are needed. In single roof, if rafter feet are not tied together by means of a roof joist or binder, then this roof will have a tendency ,under weight ,to push the supporting walls outwards at top causing structural failure of the wall. Hence in larger span of roof, single roof is not recommended.

The various forms of single roof are as follows:

(a) Lean-to-Roof:

The lean to roof is defined as single slope roof with its upper edge adjoining a wall or building.

Lean to Roof
Also Read: Lean to Roof

(b) Couple Roof:

The couple roof include two lengths of timber (rafters) leaning against each other, tied where they meet at the top.

Also Read: Couple Roof

(c) Couple Close Roof:

Couple close roof is similar to a couple roof but the legs of the common rafters are closed by a horizontal tie known as tie beam.

Couple Close Roof
Also Read: Couple Close Roof

(d) Collar Beam Roof:

A horizontal piece of timber or any other material connecting and trying to gather two opposite rafters is called collar beam roof.

Collar Beam Roof
Also Read: Collar Beam Roof

02. Double Roof:

Double Roof is defined as a roof framing system in which the rafters rest on purlins which provide intermediate support.

In double roof, each rafter is supported at three points:

  • At the bottom; on the wall through wall plate
  • At the top; by the ridge
  • At the centre by a purlin

The basic elements of the double roof are rafters and purlins. In Double Roofs, if length of span is larger, then it requires an intermediate support. This support is usually a beam which is protected under the rafters at a point between the ridge and the wall plate. This beam is known as purlin. Purlin is used to reduce the size of the rafters and to make structure in economical one. Double roof construction is simple than other roof.

Also Read:

All You Need to Know about King Post Truss
What is Shell Roof?

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