Single-Ply Membrane: Polyvinyl Chloride (PVC)

Single-ply membranes are factory-manufactured sheet membranes. They generally are categorized as either thermoset (EDPM) or thermoplastic (TPO or PVC). Thermoplastic materials can be repeatedly softened when heated and hardened when cooled. Thermoset materials solidify, or "set," irreversibly after heating. Single ply membranes commonly are referred to by their chemical acronyms, such as ethylene propylene diene monomer (EPDM).

Single-ply sheet membranes are produced using one of three manufacturing processes: calendering, extruding or spread coating. The membranes may contain reinforcement layers. Common reinforcements for single ply membranes include polyester fabrics or scrims, glass fibre, or a felt or fleece backing.

A finished sheet’s thickness typically is referred to as mil thickness. Common mil thickness for these sheet membranes ranges from 30 mils to 60 mils. Single-ply membranes can be installed fully adhered, mechanically attached or held down with ballast. Most single-ply roof systems do not receive surfacing. In many instances, a combination of attachment methods is used to secure a roof system.

For instance, an insulation may be mechanically attached to the substrate with the roof membrane fully adhered to the insulation.

What is Polyvinyl Chloride (PVC)?

PVC sheets are produced by calendering, spread coating or extruding, and typically are reinforced with polyester or glass-fibre mats or scrim. PVC sheets contain plasticizers and stabilizers, as well as other additives to impart flexibility and achieve other desired physical properties. Some membranes are available with nonwoven fleece backing adhered to the underside of a sheet.

Sheet widths range from 6 feet to 12 feet wide.
Sheets are typically 45 mils to 90 mils thick.
Seams are sealed by heat or chemical welding.
PVC membranes are produced in numerous colours, though grey and white are the most common.