Performance Advantages
The traditional coal tar system is a built up roof that is manufactured on site, with layers of felts adhered to the roof using hot-applied coal tar pitch. It is the coal tar that protects the roof from the elements, while the felts act as reinforcement. Simple though this sounds, the impregnability of coal tar, even in this basic configuration, ensures lasting protection against the elements.

Coal tar's molecular structure provides the extraordinary benefit of actually healing itself as it begins, like all organics, to succumb to natural degradation. Specifically, any cracks that might be formed by impact or rapid drops in temperature, reseal when surface temperatures rise and the coal tar softens. These self-healing properties provide a long-term roofing solution that will require less maintenance than most roofing systems.

To counteract its low softening point, coal tar roofing requires surfacing with gravel, which provides a durable surface for roof traffic. Coal tar's unique chemical properties allow it to remain insoluble in water, explaining why many coal tar roofs are preferred for roofs with ponding water. Unlike most roofing materials, coal tar shows good resistance to attack from most organic compounds. Hydrocarbons, gasoline vapors, exhaust fumes, and cooking oils and fats do not affect coal tar, making it ideal for applications that require some chemical resistance. Attributes such as these have made coal tar roofing a long-term solution for flat and low-slope roofs for decades.

Today’s Technology
Unlike traditional coal tar systems, some of today’s advanced coal tar technologies are remanufactured, combining the proven durability of traditional coal tar with polymer modifiers in a quality-controlled factory environment. The resulting cap sheet is then installed in the field using a built-up configuration. The application method is versatile, allowing building owners to choose hot tar or cold adhesive as appropriate to an application’s height, logistical considerations, and health and safety concerns.

With such products, the coal tar protects the polymer additive from degradation, allowing the sheet to maintain the inherent benefits of the polymer. The cap sheet combines the proven performance of coal tar with the enhancements of polymer-modified bitumen roofing to provide a long-term solution ideal for most flat or low-slope applications.

In essence, such roofs offer the low-temperature flexibility and aging benefits of polymer-enhanced asphalt-based systems, while replacing the asphalt with coal tar chemistry for optimum waterproofing effectiveness. In addition, these high-performance systems have a higher softening point, providing two additional benefits: they can be installed on roofs with slopes as high as ½:12 and offer the aesthetic options of mineral and smooth surfacing, in addition to traditional gravel.

Health and Safety Innovations
Health and safety concerns in relation to coal tar have primarily focused on two areas: skin exposure and fume inhalation. To address these issues, roofing manufacturers and developers of ancillary equipment have developed a variety of innovative technologies.

Since both problems appear to be attributable to fumes, the roofing industry's goal has been to minimize fumes without adversely affecting much-coveted waterproofing performance. After decades of testing and development, the industry has introduced several low-odor coal tar technologies that can be used in traditional BUR systems or as restoration coatings for built-up and modified gravel-surfaced roofs. Such systems retain the self-healing properties of coal tar, while sometimes enhancing other performance characteristics, such as UV protection, cold-weather flexibility, or resistance to thermal shock or impact.

Another innovation, fume-reduction kettles, virtually eliminate the odor associated with coal tar BUR installations. These devices are simple to use, have no filter to clean or replace, and their exhaust is clear and 98% odor free.

In addition, the aforementioned polymer-modified coal tar cap sheets can be applied using a solvent-based coal tar adhesive, eliminating the need for high-temperature kettles. The solvent dissipates over time, and has no adverse effects on the coal tar roof system's performance. Such applications significantly reduce the fumes caused by traditional coal tar applications.

It should also be noted that OSHA has introduced comprehensive guidelines to help ensure worker safety, for example, recommending full-length shirts and trousers, the use of sun screen, and so on.

Conclusion
A roofing industry anxious to provide lasting solutions for tough applications has risen to the challenges posed by traditional coal tar with innovative system configurations, adaptive chemistries, and problem-solving equipment. As a result, those users desirous of long-term results for applications prone to water penetration can once again, with confidence, take advantage of the time-proven benefits of coal tar technology.