The roofing industry initially was reluctant to adopt the new synthetics. By way of comparison, the industry literally had decades of experience with modified bitumen. As a result, residential roofing contractors were eager to adopt the premium self-adhering underlayment and these were readily accepted by the industry as a premium underlayment.
For residential roofing, it has been argued that the underlayment need only shed water because of the steep slopes of the roof. And furthermore, the primary roof (whether shingle, tile, metal or other material) protects the underlying material from ultraviolet radiation.
Such arguments led to the idea of using an extremely thin layer of plastic as an underlayment. But experience with the synthetics was lacking. Synthetic underlayment gained notoriety as being unsafe because the sheets would become slippery when wet. Especially the early versions were deemed unsafe and hence many contractors preferred to use familiar materials.
Synthetic materials allowed water to be drawn through fastener holes through capillary effect. The plastic would stretch and surface tensions would allow water to wick through the hole, alongside the fasteners. The result is that the so-called secondary water barrier would leak.
Staples were not suitable for fastening these thin plastic sheets. Furthermore, despite claims of labor savings, they were sometimes difficult to install, especially under windy conditions, because of their flimsy, lightweight construction.
Another factor that made roofing contractors wary of synthetics was the large number of companies entering the marketplace. Caveat Emptor (let the buyer beware) supplanted experience and industry standards. The fact that many of these new underlayment companies were completely unfamiliar with the roofing industry did not help with the product development.
Another drawback of polymers is that they are typically provided as thin sheets that could leak if punctured. Users of single ply roofs made of thermoplastic olefins (TPOs), rubber (EPDMs) and other polymers have long struggled with this drawback. A “single ply” plastic roof typically does not make a reliable, long-lived primary roofing material. Even if the roof escapes being punctured, prolonged exposure to ultraviolet radiation severely compromises the life cycle of single ply roofing systems. Roofers and building owners have struggled with such roof materials in low-sloped, commercial roofing applications for decades.
Nonetheless, in some regions of the country and for certain residential roofing applications, roofing contractors quickly began adopting synthetics. Market growth and market share have in some cases surpassed double digits.