May 1996

One of the main advantages inherent in all flexible membrane roofing systems is the quality control imparted to the products during their manufacture in factories. Each membrane type offers additional unique features and characteristics which will make them well-suited for use in roofing applications. This is the first in a series of three columns which will focus individually on each of the three main categories of flexible membranes, thermoplastics, thermosets and modified bitumens and on their particular qualities and characteristics.

Thermoplastic roofing product success today is based on a history of product chemistry and application technology evolution that has passed the test of time. Thermoplastic materials were first identified as appropriate for use as roofing membranes in Europe during the 1960's. Early formulations were based on PVC (polyvinyl chloride) polymers which were compounded with plasticizers for flexibility, stabilizers for UV resistance and dimensional stability, reinforcements for strength and dimensional stability, and pigments for aesthetic appeal. Today, many products are available which still contain these basic elements; others have been introduced which contain other ingredients, but which exhibit similar basic performance characteristics.

One of the very earliest recognized benefits of these membrane systems relates to their seaming technology, the most critical area for flexible membrane performance. Thermoplastic materials, be definition, can be joined together by chemical or heat welding, both of which produce permanent bonds of extremely high strength. For roofing, heat welding is preferred and special manual and automatic welding equipment has been developed to produce fused, impermeable seams. The equipment which is clean, readily maintainable and easy to use, can be adjusted to accommodate different ambient weather conditions to maximize seam integrity. The result of the product and application technology is increased labor savings with improved quality performance in all seasons.

Another characteristic of thermoplastic roofing systems is their versatility. Their ability to be installed fully adhered, mechanically fastened as well as ballasted ensures their applicability to almost any roofing situation. Barrels, domes, and steep slopes can be accommodated as well as large expansive flat roofs. Industrial buildings, airports, and huge factories have all realized the benefits of thermoplastic roofing, as have small strip malls, individual fast-food or convenience stores and institutional structures such as schools, museums and hospitals.

Many formulations allow for the inclusion of special UV-stable pigments which may be used to enhance the appearance of the roofing material. This feature won broad appeal among designers and some building owners who are desirous of including the roof as a part of the overall building design. In some cases, specific color matches with other building elements, such as weathered copper or brick, have been achieved; other roofs have corporate designs or logos welded to the roof surface as a means of permanent "aerial advertising."

A further benefit of thermoplastic roofing materials is their ease of maintenance and repair. When properly formulated and installed, these materials have demonstrated service lives in excess of 15 years. Periodic inspections should be performed as with any roofing systems; the remedy of problems for normal "wear and tear" is generally uncomplicated. Because of their chemical make up, they do not require recoating, resurfacing, or resaturating for them to retain their as-manufactured properties. Any tears, cuts or seam openings are easily corrected by using the same welding techniques as are originally used. Installation of new fixtures or penetrations through the roof surface is easily achieved by joining new flashing material to the in-place installation. This feature readily translates into lower maintenance costs, as smaller amounts of materials and less labor are required for their completion.

Through decades of positive experience, in climatic conditions ranging from tropical to arctic, on the most highly prestigious projects, on roofs covering priceless objects, records, equipment and processes, thermoplastic membranes have shown themselves to be roofs for all reasons, which protect in all seasons.

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