There are numerous reasons to specify or reroof a residential or commercial project with built-up or modified bitumen systems because they offer outstanding durability and exceptional longevity.

Many manufacturers offer a spectrum of systems that can be adapted to virtually any climate zone and building site challenge. These systems can be installed in a variety of techniques that allow maximum flexibility. Multi-ply roofing systems can be constructed with hot asphalt, mechanically attached, cold applied with adhesives, heat welded or self-adhered.

The ability to install a variety of systems using a wide range of application methods in different environments allows the products to be used in a greater time window for construction, avoiding logistical problems and delays that may occur with other alternatives. Given the current economic environment, this scheduling criticality may give construction professionals who use multi-ply systems a clear advantage.

Additionally, in some geographical areas, code regulations necessitate the use of low VOC materials, particularly with occupant-sensitive structures such as hospitals and healthcare facilities. The use of self-adhesive modified bitumens with very low odor or fumes is an excellent choice, as are some hybrids.

As LEED® and other green initiatives increase the demand for low-slope commercial roofs with sustainable attributes, multi-ply asphaltic membranes have also evolved with the times to offer state-of-the-art reflective cool roof systems. This material also serves as an excellent membrane base for certain vegetative systems that are modular or containerized. More than ever, consideration is being given to ways to mitigate the urban heat island effect in major cities across the county and multi-ply systems can be a very effective choice, especially when the insulation systems are optimized.

In addition, some new studies reveal that multi-ply systems may be better suited for photovoltaic applications, because temperature differentials may be less than experienced with single ply installations. Designers understand that less temperature extremes over time may reduce the possibility of thermal fatigue.

Multi-ply membranes are also beneficial because they create a more rigid and stable surface that make the roofing system a better platform for a building’s mechanical systems, solar energy systems, vegetative (roof gardens) or creating usable outdoor space.

The multiple layers of bitumen and bitumen-saturated “felts” make a watertight barrier capable of providing many years of reliable protection from the elements. If a top layer is damaged, the subsequent layers underneath provide a back-up layer to prevent water and the elements from entering the building.

Both Underwriters Laboratories® and Factory Mutual (RoofNavSM) list thousands of multi-ply systems as meeting tough fire resistance requirements and ensuring adequate wind uplift conditions, resulting again, in a multitude of choices. The variety of ply substrates, whether reinforced with fiberglass, polyester or a combination of both, gives an exponential number of options over single ply systems, especially in high wind zone or hail prone areas.

Installing a built-up roofing system could also save a property owner on heating and cooling costs because of its resistance to the conduction of heat between the exterior and interior of a building.

In terms of maintenance, data presented by Carl Cash from the proceedings of the RCI 21st Annual Convention & Trade Show demonstrate that granular surfaced SBS multi-ply systems have one of the lowest maintenance costs per square foot of all systems studied.

Most Asphalt Roofing Manufacturers Association (ARMA) member manufacturers and suppliers have rigorous contractor programs in place to assure that quality is paramount. Given the redundant nature of multi-ply systems, this “belt and suspenders” line of defense against the elements should bring peace of mind. These same members have made significant investments in materials science and production technologies, bringing R&D and process discipline to the manufacturing process as well.

The ARMA organization is committed to furthering the specification and use of multi-ply bitumen systems and can be a valuable resource for building owners. For comprehensive information on asphalt roofing systems, please visit