The purpose of this report by Kingspan Insulation is to examine alternative methods of satisfying the requirements of Building Regulations / Standards for flat roof construction. The report uses 3 case studies to examine alternative ways of achieving the new requirements.
The case studies are for new build non-residential projects with warm deck roofs only. Refurbishment is not covered. The designs are based on achieving the new values as an average across the whole roof, not as a minimum at all points. The case studies are of varying size and complexity:
Case Study 1: A relatively small rectangular roof plan with simple falls.
Case Study 2: A slightly larger complex roof plan with more complicated falls.
Case Study 3: A much larger roof plan with relatively simple falls
Three design options have been costed for each case study: falls achieved by screed laid to falls; falls achieved by use of tapered insulation; and falls achieved by use of timber fittings under plywood base (more usually associated with timber or metal deck roofs).
The three case studies all employ a concrete sub-base but the conclusions regarding tapered insulation compared with timber fittings would be equally valid in a metal deck roof situation. It is unlikely that a screed would be used with a metal deck roof.
In all three studies, the tapered insulation solution has been shown to be the cheapest.