What is single ply?

Single ply is a complete roof system

It is created from strong and flexible membranes composed predominantly of synthetic polymer.

The thickness of single ply membrane is in the range 1.1mm to +2mm. Some products are homogenous, others are reinforced with glass fibre or polyester, depending on the application. Membranes are sealed at joints to form continuous waterproofing. When combined with insulation and continuous support, they form complete, durable roof systems.

Membrane Types

  • CPE – Chlorinated Polyethylene
    • Polyethylene is made flexible by chlorination and can be heat or solvent welded. Generally, CPE is compatible with bitumen.
  • EPDM – Ethylene Propylene Diene Terpolymer
    • EPDM is a naturally flexible material to which carbon black is added for stability. Jointing is normally carried out with tape bonding using a special primer, but adhesives can also be used. EPDM is compatible with bitumen.
  • FPO – Flexible Polyolefin
    • FPO is a large family of heat-weldable polyolefin based upon polyethylene or polypropylene. Preparation of the lap prior to welding may be required.  FPO-based membranes are generally suitable for direct contact with aged bitumen. Generally FPO based membranes can be recycled back into themselves or into another product.
  • PVC – Polyvinyl chloride
    • A flexible form of PVC due to the addition of high molecular weight plasticizers, which can be heat or solvent welded (depending upon the product). PVC-p-based membranes are generally not suitable for direct contact with bitumen unless a suitable weight of fleece backing is incorporated to separate the two
  • TPE – Thermoplastic Polyolefin Elastomer
    • A particular group of polyolefins with the basic properties of elastomers but which can be processed as thermoplasts. They exhibit a high resistance to UV /Ozone exposure and do not absorb moisture. Laps are heat welded without production of fumes or smoke. The wide temperature range for welding enables secure welding of seams in differing climatic conditions.
  • PIB – Polyisobutylene
    • PIB incorporates carbon black to provide good physical properties. PIB products available on the UK market are generally solvent welded using tape systems. and are compatible with bitumen.
  • VET – Vinyl ethylene terpolymer
    • VET consists of PVC made flexible by blending with Ethylene Vinyl Acetate (EVA). VET can be heat or solvent welded and is compatible with bitumen.

Types of System

There are two types of arrangement of components – ‘warm deck’ and ‘inverted warm deck’. The technical flexibility of single ply means that there are several combinations of system type and method of attachment to suit particular design conditions.

NOTE: 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.

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