A Comparison of Built-up and Foam Roofing Systems
By Texas A & M LaboratoriesIn 1974, dissatisfied with performance of traditional tar and gravel built-up roofing (BUR) systems, the Physical Plant Department began looking for viable roofing alternatives. The BUR roofs were constantly leaking, and because of the nature of BUR, leak detection was virtually impossible.
As the Physical Plant Department began soliciting information from various roofing sources and checking references, sprayed polyurethane foam (SPUF) roofs exhibited advantages that seemed to fit the criteria of the University. The Physical Plant Department found the following:
1. Seams are one of the major sources of leaks in roof systems and SPUF roofs are totally seamless.
2. Water does not travel laterally in SPUF roofs as it can in BUR or single-ply roofs. A leak in the top membrane of a BUR or single-ply roof will create the spreading of water, saturating the insulation and causing multiple interior leaks. With SPUF, even if a hole is punched through the entire thick membrane, water movement will be restricted to the hole. In most cases, repairs can be made with a tube of exterior caulk.
3. Because the SPUF roof is light weight, permeable and fully adhered, normally an old roof does not need to be removed in order to apply a new one. If underlying areas of saturated insulation are found, minimal tear-off may be required.
4. The SPUF roof is less disruptive to students and faculty since tear-off is minimal. Also, projects are accomplished faster because the application is quieter, quicker, and requires far fewer laborers.
5. Roof mounted units, penetrations, curbs, and parapets can receive a seamless monolithic application because SPUF is spray applied. BUR and single-ply roofs require flashing material with sealants which frequently result in leaks.
In 1974-75, convinced the preceding advantages warranted taking a look at this relatively new roofing system the Physical Plant Department issued contracts for the reroofing of several buildings. One of the earliest roofs done with this system was Davis-Gary Dorm. After seventeen years this roof has not leaked and requires minimal maintenance.
Between 1975 and 1977 the Physical Plant Department and TAMU Systems Facilities Planning and Construction (FPC) communicated back and forth concerning the monitoring of these roof installations. New BUR roofs were providing the University with service life of less than five years, and many of the BURs were leaking from the onset. In 1977 the Physical Plant Department foamed over a BUR that was less than four years old. After monitoring the SPUF installations, the FPC was also convinced and since 1977, all new roofs have used SPUF roofs.
FPC received numerous complaints stemming from this decision. Few roofing contractors had the financial ability to mobilize spraying foam. Fewer still had the caliber of crews that are needed to formulate foam in the field. Though this eliminated potential bidders, it in effect greatly elevated the caliber of roofing contractor working at Texas A & M.
Many outside architects working at the University were unfamiliar with the system, and some were reluctant to learn anything new, but the Physical Plant and FPC were adamant. As time went by, architects and general contractors learned the many advantages of the system. This caused proliferation of the SPUF roof systems in surrounding school districts and Universities.
Today over 7 million square feet of SPUF roofing has been applied throughout the A & M system. With very few exceptions, these roofs are holding up extremely well. In fact, it is extremely rare that one of these roofs leaks at all. Blister defects which occasionally occur do not create leak problems. Most of these defects are covered by warranty with no expense to the University. Most of the leak problems occur on the few campus buildings that still have BUR on them.
In 1985 the Physical Plant Department found another advantage in using SPUF roofing systems. For a number of years, Mr. Gerald Scott, P.E. was in charge of roofing and energy conservation within the Physical Plant Department. Vendors of the SPUF system always championed the energy saving characteristics of the system. We realized polyurethane was a most effective insulation, but our main concern had always been to prevent roof leaks.
Mr. Scott monitored energy savings on 27 different buildings that had received SPUF roofs from 1980 to 1984. The results were astounding. TAMU was able to recover the complete cost of the roof application through energy savings in an average of four and one-half years.
Quoted here is Mr. Scott’s which is still shared by today’s Physical Plant Department. “From the time of construction, and throughout the life of the roof, built-up roofs were major maintenance and repair items. The experience that the Texas A & M University Physical Plant gained since 1974, when they began, indicates that no major problem, and very few minor ones exist in the polyurethane roof systems. As a result of this experience, all new construction includes the foamed polyurethane roof system. To date some 16 new facilities have this roof system totaling nearly one million square feet.”
Another major advantage in a SPUF roof system that does not exist with any other roofing system is that SPUF is a renewable system. While BURs and single-plys must be removed and replaced after their usable lives. SPUF roofs can be repaired and recoated to offer an indefinite life expectancy. Coupled with the energy savings and reduction in in-house maintenance costs, the SPUF roofing system maintains a tremendous long-term cost efficiency advantage over all other roofing systems. Without question SPUF roofs have a tremendous edge in preventing leaks and in detection and repair when one does occur.
The conclusion of today’s Physical Plant Department has not varied from the conclusion reached by Gerald Scott in 1985. We at the Physical Plant Department continue to monitor the progress of other roofing systems available. But at this time, no other roofing system can offer the leak-free service, the ease of leak detection and maintenance, the energy efficiency, durability, or renewability provided by sprayed polyurethane foam roofs.