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Design Criteria for Single Ply Roofing

Designers and specifiers have been exploiting the potential of single ply for nearly 40 years. This technology offers a huge range of geometric and performance options. Specify SPRA to get to the most experienced providers in the industry.


06 SPRA DesignGuide fc

SPRA Design Guide 2016 is now available to download HERE. Now forty-seven pages, the new Guide hyperlinks to all other SPRA Guide and Quality Standards, together with many vital industry references. Over twenty-five years, the Guide has reflected the transition from prescription and standard 'solutions' to a more performance-based construction process based on harmonised European Standard. Judging from the feedback I get, it's very highly respected amongst our customers out there. So what's new?


The new edition recognises the key importance of designing for future storm events, in new construction and refurbishment:

* The importance of a secure substrate on which to mechanically fasten perimeter trims.

* New advice on ballast requirements in high wind load situations.

* Recognition of Factory Mutual Data Sheet 1-29 (January 2016 version): 'Roof deck securement and above-deck roof components' and 1-49 'Perimeter flashing'.

* Link to the new SPRA 'Wind load – a guide to reduced risk' including the new 'Checklist for wind load calculation'.


There is extended advice on design for effective drainage, including options for creating falls in different types of deck. SPRA fully supports the requirements of BS6229 in respect of a minimum finished fall of 1:80 at any point in all roof systems and recognises the potential risks to thermal performance of allowing back-falls on inverted roofs.


The need to attenuate potentially high loadings on urban storm-water systems has been recognised for a decade. The Guide recognises the advantages of green roofing as a natural attenuator and of roof or ground-level storage as an option, but notes that any design which deliberately stores a head of water on the waterproof membrane requires a completely different approach. Like other manufactured membranes for roofing, certification does not extend to situations of hydrostatic pressure and is not within the scope of BS6229.


There is new advice on loading of roof systems by pedestrian finishes. The use of timber decking has increased dramatically, partly driven by the London apartment boom but also by fashion. There are rewards and risks, not least durability and access to rainwater outlets, all of which will be covered in a new guide to be developed in consultation with the Timber Decking and Cladding Association.


Although there is no sign of the draft for the 2016 revision of Approved Document Part L, the Guide includes a new section on the 2013 AD, with improved detail.


For further information please contact Jim Hooker, Technical Director at SPRA by emailing This email address is being protected from spambots. You need JavaScript enabled to view it.

















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