Flat Roof Checklist Part 2: Aesthetics and Structure

The chosen construction of a building is a very good indicator of the ideal roof structure and waterproofing solution.

Commercial or industrial units are frequently built using large, lightweight steel frame structures, and large residential low rise are sometimes lightweight timber frame. These lightweight structures give you less freedom with roof loading and would favour lightweight roof structures and finishes.

Other buildings such as high rise residential, public and civil buildings such as hospitals, may be constructed using dense masonry where a heavier roof structure is possible and may be desirable when other factors are taken into consideration such as longevity and protection.

For example, on dense concrete structures where access is required, one might consider hot melt or liquid more favourably than single ply, as the membrane would usually be buried with ballast on top. Whilst single ply can be used in this situation, special attention would need to be paid to protecting the membrane both during and after installation, which makes its use more complicated.

Identify the likely construction as concrete, steel or timber, and consider the size of spans, and this information will lock out some waterproofing options and suggest others.