What is a PVC roofing system?
Polyvinyl Chloride, commonly referred to as PVC, is a single-ply thermoplastic roofing membrane, primarily used on commercial and industrial roofing systems. PVC-based membranes first started gaining market share in Europe in the 1960s. While newer thermoplastic membrane formulas such as TPO have entered the single-ply market share, these formulas are often considered untested and unproven since they haven’t been around long enough to establish definitive track records. Because PVC systems have a proven track record of durability and versatility, they remain an active and growing competitor in the single-ply roofing market.
PVC-based membranes are widely noted for their thermal resistance and reflectivity, allowing building owners to reduce heating and cooling costs. The membranes are available in a variety of colors and sizes, and some manufacturers offer options that allow for rooftop logos, graphics, and slogans. PVC is also noted as being fire resistant, and it has self-extinguishing capabilities when subject to open flame.
Unlike EPDM systems that use splice tape to waterproof seams, PVC systems, along with their TPO competitors, use hot-air weldable seams, in which a steady stream of hot air is injected between the overlapping membranes, literally welding the membrane together to create a solid monolithic field sheet.
How are PVC roofing systems installed?
There are three primary methods of securement for PVC membranes:
- Fully adhered.
- Mechanically fastened.
Fully adhered PVC systems use special adhesives to secure the membrane to the insulation board and roof decking.
Mechanically fastened PVC systems use manufacturer approved hardware, usually consisting of specially designed plates and fasteners, to mechanically secure the membrane to the insulation and roof decking below.
Ballasted PVC systems are loose-laid and are secured only at the roof’s perimeter and penetrations. The entire roof is then weighted down with round river rock and/or large concrete pavers to hold the membrane in place.
After the method of securement has been chosen, overlapping membranes are hot-air welded together to create a solid monolithic field sheet. Most pipe penetrations on the roof deck are sealed using factory-fabricated pipe boots which are then hot-air welded to the field sheets. All corners, T-joints, and other possible water channels are sealed by hot-air welding PVC-based flashing membrane to the field sheets. The installation of such materials requires the skill of a trained roof technician to ensure that all membrane is properly laid and that all hot-air welds were done at the required temperatures, so as not to compromise the durability and integrity of the new roof.
What type of maintenance is required on PVC roofs?
A properly installed PVC system will require little maintenance over the life expectancy of the roof. Required maintenance will vary by climate, how much foot traffic the roof receives, how quickly the roof sheds and evaporates water, and how much organic and non-organic debris the roof will be subjected to. Typical maintenance on behalf of the roof owner usually involves simple cleanup of excess debris to ensure that all drains and designated water channels stay opened and unclogged. Repairs on PVC systems should be done by a trained roof technician.
What is the life expectancy of a PVC roof?
Most manufacturers offer warranties on PVC systems ranging from ten to thirty years. The warranty will vary depending upon the thickness of the membrane used, the size of the welded seams where the membrane overlaps, the methods used to secure the membrane at walls and perimeters, the climate and environmental conditions the roof is subjected to, and ultimately on the quality of the workmanship performed during the roof’s installation.
Most manufacturers will not warrant a roof until one of their own inspectors has visited the site and verified that the contractor has properly followed their specifications for installation. The manufacturer’s inspection is a strict and orderly process that ensures the roof in question will meet and exceed the requirements of the desired warranty.