Prefabricated roof curbs have been in use since the roof has been utilized for something other than keeping weather out. And in this one sentence lie the benefits and the detriments we face in the roof curb business everyday. The primary function of the curb is to keep weather out while supporting/flashing the equipment on it.
You could say that everyone who makes equipment for roof mounting is “in the curb business” as well, but with many companies their focus in not the roof’s integrity, but rather the support of their equipment. Hence, the lack of certain items such as insulation, wood nailers, cants, etc. Not only are these items not included, but you may have as many as three or more subcontractors involved with different applications.
Mechanical applications involve exhaust fans, rooftop HVAC units, electrical generators, exhaust ducts, vent pipes, refrigeration lines, etc. Architectural applications include unit skylights, structural and monument skylights, terminations at walls, expansion joints, roof hatches, heat and smoke vents, and satellite dish systems.
The advantage of an integrated curb system addresses all these applications, as well as the curb interface with the roofing systems, which offer yet another set of variables to consider.
The Roof ComponentsFirst, the basic design of the curb should take into account the roofing components so that it can be properly flashed into the roof system. A canted curb, for example, should be used for a built-up or modified bitumen system roofing system. Full-service curb manufacturers offer this type of diversification and coordination with a given roof system by offering curbs which are canted, non-canted, raised canted, self flashing, or designed and manufactured to match the exact profile of a pre-engineered metal roof system.
Second, the curb should be available in a variety of heights depending upon geographical location and be available with pitch factory-built into the curb since most roofs are sloped for drainage in some manner.
In addition, the curb system should be available with options such as metal liners covering the insulation in certain applications. Special designs can be used to satisfy seismic criteria, Miami-Dade County codes, or other region-specific criteria. Curbs should be available with sound baffles to satisfy noise criteria in certain applications.
Specialty flashing curbs should be available to replace “pitch pockets” when running pipes, conduit or tubes through the roof. For those pipes and ducts running across the roof, supports that bear directly on the roof deck as recommended by the NRCA are equally important to the overall roof integrity. All of this constitutes a system.
The SystemWhat does the client get with a system? A professionally finished roof which will ultimately save him money for the life of his investment. What will you, the roofing contractor, get from a complete system? First of all, you’ll achieve symmetry of design, as all curbs will be of the same design and specific to your roof. You’ll also receive the benefits of predictable, consistent deliveries, and the curbs will be there when you need them for your work, not months later when the mechanical units show up. With a complete curb system, curbs are always NRCA compliant, and they are cost-effective because you, the roofer, won’t have to return one or more times to flash someone else’s curbs. Most importantly, no other trades will be messing around with your roof.
What is needed to achieve the use of such a system is a twofold approach. The curb industry has, for years, promoted such a system and has developed and improved the design specific criteria mentioned above. This will be continued by aggressive promotion to the design community and participation in aggressive advertising campaigns and attendance at trade shows.
But the roofing industry needs to take a better stand in the design process by recommending the use of a curb system as outlined above in an effort to make known that its belief and trust in the use of such a system is paramount in the team effort to build better roofs.