In spite of changing fashions, the pitched roof remains the
most popular roof shape for domestic and public buildings simply because it is
the most efficient at shedding water.
Also, the overlapping roof tile and double-lap slate are the most popular coverings
because they are durable, inexpensive, easy to lay and widely available. Moreover,
their simple rectangular shape, easily cut, and a wide variety of colours and
textures allow it to be used on a vast range of roof shapes and designs with
confidence, flair and economy.
The design of a pitched roof is dictated initially by the
shape of the building, the span between the structural elements and the use to
be made of the space enclosed by the roof. Although traditional roof
construction, in which rafters and purlins are cut and fitted on site, has
largely been superseded by the use of pre-formed trusses, the current move
towards using the roof space for accommodation has prompted developments in
attic truss design, requiring a lightweight roofing material, for which fibre
cement slates are so suitable.
After structure and function have been taken into account, the
design of the roof may be modified by other considerations, such as weathering
The easiest roof to design and construct, especially if
pre-formed trusses are to be used, is the gable-to-gable shape. Because of the
simplicity of this design, interest is often created by the addition of gable
parapets, dormers, projections to the plan shape, or special features in the
slating. Both the appearance and the weathering of the roof can be improved by
the use of hipped ends in place of gables, but these require a more complex and
costly structural frame, and also more elaborate detailing.
Types of roof
The pitched roof covered with tiles or slates offers the
designer a vast choice of roof shapes. Whatever the shape and finish of the
accommodation below, it is the design and detailing of the roof that probably
has the greatest influence on the appearance and effect of the building as a
Some examples of the variety of roof shape available are shown
below, but many more combinations are possible.