Flat roofs are normally constructed with timber joists supporting a plywood decking which has a waterproof membrane on top. Most membranes for residential construction are high performance felts, which have a life of around 30 years. The insulation can be put on top of the decking (warm roof construction) or below (cold roof construction). Warm roof construction is generally regarded as being better.

We need the following information to design a flat roof:

the span of the roof joists

the use of the roof (ie will it just be a roof or will it be paved and be used as a terrace)

the approximate location of the property

details of any parapet walls, or walls adjacent to and higher than the flat roof

Design information

All design work is carried out in accordance with BS5268 (The structural use of timber).

The calculations provided will be suitable for Building Regulation approval.