C&G PowerPoint Type of roof and components

Level 3 Diploma in Site Carpentry

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Unit 306: Carry out first fix roofing and stairs

Types of roofs and component parts



Aims

•To understand how to construct a traditional cut roof

•To identify and describe different types of roof

•To identify and describe the components used to construct a traditional cut roof

Introduction



Types of roof

Source: Concerca



Types of roof

Flat roof: These roofs are not actually flat as it has pitch of up to 10º.

Lean-to and mono-pitch roofs: These have a single sloping surface. The lean-to roof abuts a wall or building and is mainly used for extensions, whereas mono-pitched roofs are free-standing.

Gable-end roofs: These have two sloping surfaces (double-pitched) terminating at one or both ends with a triangular section of brickwork called the gable.

Hipped-end roofs: These are double-pitched, with the roof slope returning around one or both the shorter sides of the building to form a sloping triangular end.



Types of roof

Mansard roofs: These are double-pitched, whereby each slope of the roof has two pitches on each side. The lower part has a steep pitch (to act as walls) and usually has dormer windows for rooms in the roof applications. The top pitch is 30º or less. The ends of the building may be finished with either gable or hipped ends.

Gambrel roofs: These are double-pitched and incorporate a small gable or gablet at the ridge and a half-hip below. The gablet may be finished with tile hanging, timber cladding or a louvered ventilator. Mainly seen as farm buildings.

Jerkin-head roofs: These are double-pitched roofs, which are hipped from the ridge a short distance down the gable wall. These are also known as Dutch hipped roofs.



Types of roofCouple roofs: These consist of pairs of rafters fixed at one end to the wall plate and at the other to the ridge board. Without a tie (ceiling joist) to the feet of the rafter, the span is restricted up to 3.5m because the forces that act on it will spread the walls.

Source: Concerca



Types of roofClose couple roofs: These are similar to the couple roofs, although the feet of the rafters are closed with a tie. This enables the span to be increased. The tie also acts as the ceiling joist. In addition, a central binder may be fixed to the ceiling joist, hung from the ridge at every third or fourth rafter spacing, to prevent any sagging in the ceiling joists.

Source: BarkingDog



Types of roofCollar tie roofs: These are similar to close couple roofs, although in order to increase the span the tie is moved up the rafter by a maximum of one-third of the rise.

Source: BarkingDog



Types of roof

The rafters of a double roof are of such a length that they require an intermediate support by purlins in their mid-span. This effectively reduces the span of the rafters and limits their size to economical sections. Struts, collars and hangers are spaced evenly along

the roof at every third or fourth pair of rafters to provide intermediate support for the purlins. Binders may also be fixed to the ceiling joist to bind together and prevent any sagging in the ceiling joists.

Source: Concerca



Roof terminology

Source: BarkingDog



Roof terminologyRidge: The backbone of the roof that provides a fixing point for the tops of the rafters, keeping them in line.

Wall plate: Transfers the loads imposed on the roof uniformly across the brickwork. It also provides a bearing and fixing point for the feet of the rafters.

Hip rafter: Used where two sloping roof surfaces meet at an external angle. It provides a fixing point for the jack rafters and transfers their loads to the wall.

Jack rafters: Span from the wall plate up to the hip rafter and run in line with the common rafter.



Roof terminologyCrown rafter: A common rafter that is used in the centre of a hip end.

Cripple rafters: Span from the ridge to the valley and run in line with the common rafter.

Valley rafter: Like a hip rafter, but used at an internal angle. It provides a fixing point for the cripple rafters and transfers their loads to the wall.

Purlin: A beam used in double roofs that provides support for the rafters in their mid-span.

Gable ladder (also ladder frame): Fixed to the last common rafter to form the overhanging verge on a gable roof. It consists of two rafters with noggins nailed between them.



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C&G PowerPoint Type of roof and components