What is roofs and type of roofs

ROOFS

Roof is the topmost portion of the building. The roofs may be classified as flat or terraced roofs,

pitched or sloping roofs, folded plate and shell roofs.

Flat roofs They may have slight slope (not more than 10°) in order to drain rainwater. The following

types of flat roofs are popular in India: Punjab terrace roofs, Maharashtra and M.P. terrace roofs,

Madras terrace roofs, Bengal terrace roofs and R.C.C. roofs.

* Pitched/Sloping Roofs : In areas where rainfall is more or snowfall takes place, pitched roofs are

preferred. The slope of the roof may vary as much as 40° to 60°.

* Technical terms used with pitched roofs are : Ridge is apex line of sloping roof. Hip is the line

formed by intersection of two sloping surfaces, where exterior angle is more than 180°. In valleys

interior angle is less than 180°. The lower edge of the sloping surface of a roof is known as eave.

Gable is the vertical triangle of the wall supporting a sloping roof. Ridge piece is a wooden piece

providing at the ridge, which runs horizontally. Eave board is a wooden board along the eves

which hides the view of rafters from outside. Rafters are the pieces of wood which extend from

the ridge to eave. Battens are the thin sheets of wood which are fixed on the rafter to support tiles.

Wall plates are the long wooden members, provided on walls for fixing the feet of common rafters.

Post plates run over the posts and support the feet of the common rafters. Purlins are the wooden

or steel pieces that are placed horizontally on principal rafters and carry common rafters. Cleats

are small blocks of wood which are fixed on the trusses to prevent the sliding of purlins.

* Pitched roofs are broadly classified into single, double and trussed roofs.

1. Single Roofs: Lean to roof, couple roof, couple close roof, collar beam roof.

2. Double Roofs: If the span of the roof is more than 5.5 m common rafters become uneconomically.

In such cases purlins are provided.

3. Trussed Roofs: Truss is a framework of slender members. Longer halls are covered by pitch roof

using trusses at regular interval depending upon the span various shapes of trusses are used. The

trusses may be timber trusses or steel trusses.

* Various types of covering materials used for pitched roof are : Thatch, shingle, tiles, slates, A.C.

sheets and GI sheets. If A.C. sheets are used and lap should be at least 150 mm, side lap 50–120

mm. The holes for fixing should be drilled, i.e., should not be punched. Bituminous washers should

be used under GI flat washers.

* Folded plate or shells may be used to cover large column-free areas.