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Roof Development Through History

Roof type is linked to the construction period.

Velux Diagram of Roof and Loft
Velux Diagram of Roof and Loft

Roofing technology, materials and techniques have developed greatly since the 1930's and the period of house construction will have significantly influenced the system that will need converting.

Rafter and Purlin

Most older, pre War (1939) houses are the rafter and purlin type. The ceiling joists help to tie the walls, preventing the walls spreading, while purlins act as collars further up the rafters.

Often the purlins are supported on bricks rising from an internal supporting wall and wooden strips tie the purlins to the ceiling joists to prevent the roof lifting from any updrafts.

Truss Roofs

Truss Roof Timber Frame
Truss Frame

Post war timber shortage, material developments and technological innovation in roofing systems lead to many new homes being built with low, standard trussed frames. These 'W' shaped structures efficiently support a roof, and new tile systems allowed for roofs with a more gentle pitch, thereby saving on the area to cover.

A Frame Roofs

As land prices increased through the 1990s and onwards, developers began to build higher rather than wider. The A frame or attic truss grew in popularity as the roof space can be kept clear of supports and utilised as living space.

The shape of a capital A, each preassembled frame is comprised of two rafters that join at the apex, and a floor joist secured just above their base.

The advantage of this system is the simplicity of design, delivery and installation, and many trussed roofs are being converted to A-frames to bring the roof space into habitable use. This process is called a trussed loft conversion.

Flat Roof Dormers

Historically small cottage dormer windows would generally be lead clad or have a mastic asfelt flat roof, however technological innovation in the last 20 years has introduced a range of products with lower costs and excellent reliability, such as modern built-up felts, single-ply systems and fibreglass/liquid plastic systems.

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