Blog

01
Mar

A Comparison of Builtup and Foam Roofing Systems

By Texas A & M Laboratories

In 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 (SPF) roofs exhibited advantages that seemed to fit the criteria
of the University. The Physical Plant Department found the following:

  • Seams are one of the major sources of leaks in roof systems and SPF roofs are totally seamless.
  • Water does not travel laterally in SPF roofs as it can in BUR or EPDM roofs. A leak in the top
    membrane of a BUR or EPDM roof will create the spreading of water, saturating the insulation
    and causing multiple interior leaks. With SPF, 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.
  • Because the SPF 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.
  • The SPF 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
    labourers.
  • Roof mounted units, penetrations, curbs and parapets can receive a seamless monolithic
    application because SPF is spray applied. BUR and EPDM roofs require flashing material with
    sealants which frequently result in leaks.

Cross Section of SPF roofing system

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 re-roofing of several buildings. One of
the earliest roofs done with SPF was Davis‐Gary Dorm. After 17 years this roof has not leaked and
required 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 a service life of less than 5 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 4 years old. After monitoring the SPF installations, the FPC was also convinced and since 1977,all new roofs have used SPF 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.

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 SPF roof systems in surrounding school districts and Universities.

Today over 7 million square feet of SPF 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 building that still have BUR on them.

In 1985 the Physical Plant Department found another advantage in using SPF roofing systems. Mr. Scott
monitored energy savings on 27 different buildings that had received SPF 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 4 ½ years.

Quoted here is Mr. Scott’s opinion which is still shared by today’s Physical Plant Department. “From the
time of construction, and throughout the life of the roof, BUR 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 SPF roof system. To date
some 16 new facilities have this roof system totalling nearly 1 million square feet.”

Another major advantage in a SPF roof system that does not exist with any other roofing system is that
SPF is a renewable system. While BURs and EPDM must be removed and replaced after their usable
lives, SPF roofs can be repaired and recoated to offer an indefinite life expectancy. Coupled with the
energy savings and reduction of in‐house maintenance costs, the SPF roofing system maintains a
tremendous long‐term cost efficiency advantage over all other roofing systems. Without question, SPF
roofs have a tremendous edge in preventing leaks and in detection and repair when one does occur.

Conclusion

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. 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.