Single Ply Roof Membranes, What are single ply roof membranes
Single Ply Roof Membranes speaks to what are single ply roof membranes and explain single ply roof membranes.
It refers to a many ever changing group of sheet materials that are applied to the roof in a single layer.
Compared to bituminous roof membranes they require less on site labour. In comparison to built up roof membranes they are more flexible and therefore less prone to cracking or tearing as they age. Common membrane thicknesses vary from 0.035 inch to 0.120 inch (0.9 to 3.0 mm) depending on the membrane material type and the requirements of the roofing application.
Single ply membranes may be affixed to the roof deck by adhesives, the weight of ballast, fasteners concealed in the seams between sheets or if the sheets are flexible enough, with the use of clever mechanical attachments that will not penetrate the membrane.
The materials used for single ply membranes fall into two groups:
Thermoplastic materials can be softened by the application of heat and may be joined at the seams by heat or solvent welding. This welding process, which fully fuses one sheet to another, results in seams between sheets that are strong and long lasting.
The most commonly used thermoplastic roof membrane materials are polyvinyl chloride (PVC) and thermoplastic polyolefin (TPO). PVC roof membranes made of PVC resins, plasticizers and reinforcement fibers have a successful track record performance established over many decades. They are available in various colours, including reflective white for cool roofs.
However concerns over the production of toxic chemicals ( dioxin for example, a known carcinogen) during the manufacture and disposal of PVC have led to debate over how appropriate the use of PVC as a construction material. No consensus has emerged and as PVC manufacturers continue to improve their manufacturing process and initiate material recycling programs this discussion will be ongoing for some time.
Thermosetting materials also sometimes referred to as elastometrics, have a more tightly linked molecular construction and cannot be softened by heat. Thermosetting sheets must be joined at the seams by liquid adhesives or pressure sensitive tapes, which have not always proved as reliable as the welded seams in thermoplastic membrane.
Single ply membranes, unlike multi ply bituminous membranes have no redundancy and even a small defect in the joining of the sheets can result in significant leakage through the membrane.
The most commonly installed thermosetting roof membrane material is ethylene propylene diene monomer (EPDM) which is a synthetic rubber that may or may not include fiber or fabric reinforcing. EPDM has a highly stable chemical structure with excellent resistance to heat, ozone, UV radiation and weathering.
It is most commonly black in colour but is also available in cooler white from some manufacturers. Since EPDM cannot be heat welded, seaming is performed with tapes or adhesives. As with PVC EPDM has a long track record of successful performance. It is the most widely used material in North America for low slope roofs of any type accounting for up to one third of the market.
Other thermosetting roof membrane materials include chorosulfonated polyethylene (CSPE) and polyisobutylene (PIB).
Considerations
TPO roof membranes are relatively new to the North American low slope roof market. They are made from blends of polyethylene, polypropylene and ethylene propylene rubber polymers reinforced with fibers or fabrics.
TPO membranes exhibit good resistance to heat and ultraviolet radiation characteristics more commonly associated with thermosetting membranes but as thermoplastics their seams can be heat welded.
They are also available in a wide range of colours. PVC and TPO together account for approximately 20 percent of the market for low slope roofing materials. Other less widely used thermoplastic roof membrane materials include ketone ethylene ester (KEE) and a class of materials referred to as PVC alloys or PVC compounded thermoplastics made from various blends of PVC and other polymers.
Single Ply Roof Membranes
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