Key Learning outcomes
- Choosing PIR (polyisocyanurate) insulation boards for different waterproofing.
- Requirements/products characteristics of flat roof PIR insulation.
- Fixing methods for different flat roof build ups.
- Condensation risk in flat roofs.
- Understanding vapour control layers
- The dangers of hybrid roof constructions.
Introduction
A warm flat roof represents one of the simplest forms of construction – and therefore one of the best ways of achieving the fabric first principle. A build-up of structural deck, vapour control layer, PIR (polyisocyanurate) insulation and waterproofing offers reliable performance for the lifetime of the waterproofing membrane.
Unfortunately, on site constraints, particularly in existing buildings, or confusion over what the layers in that build-up do, can lead to compromises in a roof’s design and construction. These compromises can store up problems that may not be seen for several decades, but which can lead to worse-than-expected levels of thermal performance or a shortening of the roof’s active life.
Nor is it uncommon for a disconnect to occur between the designer/specifier and the roofing contractor who has “built roofs like this for years”. As an insulation manufacturer, Recticel Insulation is often asked to comment on the work of a contractor that has not met an architect’s design or does not accord with current accepted flat roofing practice.
By offering this CPD Article, we aim to demystify some common issues surrounding flat roofs, drawing on our specialism in producing flat roof insulation and the experience of our sister company, Gradient Insulation.