Flat Roof Drainage – Rethinking Construction

Summary

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.

Source: Kingspan Insulation
Report First Issue Jan 2002

For more information on this source please visit Kingspan Insulation

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