Design & Specification

The latest revision to the industry-acclaimed SPRA Design Guide 2020 has just been released. Free to download, this latest edition contains further information and updates to the previous version. The SPRA Design Guide is an essential tool for all specifiers and designers working in the single ply industry.

Why specify Single Ply?

UK designers and specifiers have been using single ply roofing systems in new construction and refurbishment for over forty years. This technology offers a huge range of geometric and performance options. Specify SPRA to get to the most competent providers in the industry.

Single ply membranes can be used in many ways. Here are some of the reasons you might choose to use them.

• Rapid construction allowing early interior fit-out
• Low capital cost and cost-in-use
• Safe, flame-free construction using hot-air welding, adhesives and fasteners
• High thermal performance using lightweight, thermally efficient rigid insulation
• Cold bridging eliminated by use of thermal break fasteners
• Effective control of air leakage to meet new energy efficiency regulations
• Minimum roof zone depth to maximise design freedom
• Easy repair, modification and refurbishment
• Simple detailing to suit all situations
• Interfaces to other construction elements
• Various colour options with matching profiles for eaves, verges and parapets
• Refurbishment
• Freedom of form-Single ply technology offers maximum freedom of choice in roof design, performance and appearance

SPRA does not recommend the use of ‘cold deck’ roofs (where the insulation is placed below the deck) because they require ventilation and it is difficult to control condensation.

Over 60% of UK construction is refurbishment and it is challenging, given the demands of carbon reduction, IT integration and safety considerations. Single ply is available in three methods of attachment and two system options, with the added bonus of compatibility with green roof systems. SPRA members have the experience to offer durable, low carbon yet attractive solutions. No use of hot materials or disruptive plant means work can often be done during continuous occupation of the building.

Single Ply roofing evaluation

SPRA have developed a simple way to evaluate the suitability of both single ply membranes and associated products for your project(s):

1) Specifying Membranes

Use the Membrane Evaluation/Substitution checklist – see Downloads

2) Specifying Insulation

Thermal and acoustic insulation is a critical component in modern roof systems. SPRA has developed ‘Component Quality Schemes’ – a set of minimum standards for entry to SPRA – that will ensure your project performs as intended. They can be downloaded and are available for:

• Expanded Polystyrene (EPS)
• Mineral Wool (MW)
• Polyisocyanurate (PIR)
• Safety systems

Safety Systems

View the SPRA  guide: ‘Safety – Design considerations for reduced risk’ in the Downloads section.

Achieving reliable details

SPRA membrane manufacturers must have a comprehensive set of details that have been evaluated for buildability and performance. Some of our members are now offering Accredited Construction Details in respect of the Building Regulations AD Part L 1 & 2.