Category: Roofs and Roof Coverings

Prefabrication of shell units has been discussed in Chapter 9. Concrete shell elements, viz., doubly curved shells, cylindrical shells, etc. which are resting on load bearing structures of buildings are erected using cranes. Figures 25.18(a), (b) and 25.19 show the erection of short and long cylindrical shells and double curvature shells. Re-course is made to…

Following are the demerits of shell roofs:

Following are the merits of shell roofs:

Based on the geometry of the middle surface, shells may be classified as: 1. Domes A dome is a type of roof of semi-spherical or semi-elliptical shape. The materials used for construction of domes are stone, brick or concrete. They are supported on circular or polygon shaped walls. Domes are preferred for covering large areas…

A shell roof is a curved surface structure. It is relatively a thin slab which is curved in one or both directions. It is often stiffened along its edges to maintain its curvature. As a shell can cover large spans without interruption of columns, shell roof is becoming very popular for industrial buildings, research laboratories,…

1. Merits 2. Demerits

It is one of the basic requirements of flat roofs. The rain water should be drained off quickly so as to avoid leakage of roof. In order to achieve this satisfactorily watertight roof surface, adequate slope and drain outlets have to be provided. The slopes in flat roofs vary from 1 in 20 to 1…

The flat roof should be made waterproof by a surface covering. The following methods are employed: 1. Cement Mortar Finishing For small buildings or normal use, the finishing of roof surface is done at the time of laying cement concrete. The flat roof is finished with cement mortar of 1 : 4. 2. Bedding Concrete…

Flat roofs are provided with a weather-proof course to sustain the effects of atmospheric agencies. The construction of waterproof course consists of providing one course of surki-concrete and two courses of flat tiles. The surki concrete (broken brick aggregate and lime with no sand) in the mix ratio of 1: 2 : 5 is laid…

This type of roof, although oldest, is cheap and fairly water-tight. It is still used in villages where the rainfall is light. This mud terrace is constructed out of good white earth containing a large percentage of sodium salts.