It’s been 50 years since James McCawley published the second edition of Roofing – Estimating-Applying-Repairing
(Shelter Publications, 1959). This was a major work, solidifying our understanding of roofing systems, and it contained chapters on membrane roofing, steep roofing, and metal
In terms of shaping the roofing industry and giving insight as to where we are today, McCawley may not be a household name. But, in his time, he made important contributions to the roofing industry, including this text.
Members of the Midwest Roofing Contractors Association (MRCA) are aware of the fact that the McCawley Award (the MRCA’s highest award) is given annually in honor of McCawley to someone in the roofing industry who has made significant contributions to our industry. But, many may not be aware of what his contributions were.
During 1939, McCawley took over as executive director at the National Roofing Contractors Association (NRCA). At the time, the NRCA had just 10 donor members (who put up $1,000 each) to keep the NRCA going. During his tenure, McCawley produced National Roofer, which he later purchased from the NRCA and renamed American Roofer and Building Improvement Contractor.
As McCauley describes in the foreword to his 1959 text, this was to be “a practical handbook describing the mechanics of shelter and the application of roof coverings of asbestos, asphalt, coal tar, metal, slate, tile, and thatch, prepared for the roofing and sheet metal trades, and as a guide for the architect and builder.”
As background for the text, McCawley explains that, back in 1955 (4 years before he published the second edition of his book), the Building Research Institute (National Academy of Sciences) convened several conferences, inviting representatives of all groups interested in the design, manufacture, and application of built-up roofing products (the dominant low-slope roofing system at the time) to focus on improving roofing performance. Looking back, McCawley’s book was the first step in working toward the Building Research Institute’s recommendations. Some of the important recommendations were:
- Better training of workmen.
- The NRCA should correlate the major roof problems and direct a coordinated program of research and investigation.
- Better flashing design.
- More accurate methods of locating expansion joints.
- Revise formulae or charts for more accurate selection of thermal insulation.
- Manufacturers’ committees develop foolproof materials and methods of installation. “An entirely new roof design based on new materials we do not now have might be the answer.”
- Improve strength and elasticity of felts.
- Develop special light-colored self-cleaning aggregate for use on built-up roofs that will protect the roof from hail and sunlight, and reduce the heat-absorbing characteristics of the roof.
- Develop better fastening devices and methods.
- Develop insulation with high insulating value that can be placed in plastic form (to eliminate joints) is unaffected by water, is impermeable, and is strong enough to support roof traffic.
- Determine the suitable job conditions for proper application of materials and advise the applicators.
Let’s review some of the Construction Industry Council’s recommendations and see how well we’ve done in this half-century …
Recommendation No. 1: The U.S. Department of Labor should initiate an intensive program designed to train all roofing workmen, especially the newer men, to know when and how to best handle and apply roofing materials.
Unfortunately, this never happened, although grants from OSHA have been made to improve fall protection and deliver safety training in Spanish.
In Canada, especially through the Roofing Contractors Association of British Columbia (RCABC), a training center is available for training roofing workers.
In the United States, for built-up roofing, training was left to the contractors while the materials suppliers provided occasional inspection before bonds were issued. Roofing unions provided well-organized worker training, mostly in larger cities, such as Chicago, San Francisco, Philadelphia, and Kansas City. There continues to be a union presence estimated at 20 percent of the current workforce.
The Roofing Industry Educational Institute was created in 1979 to provide unbiased technological information on roofing systems. Economic conditions resulted in its demise and merger with the NRCA in 2000.
Meanwhile, suppliers of newer roofing systems, such as single-ply, modified bitumen, sprayed-in-place polyurethane foam, and metal systems, recognized that intensive education was necessary for these systems to succeed. Individual manufacturers provided this education, generally at central training centers. Technical field support was provided at start-ups of projects, along with more stringent inspections than for BUR systems.
Recommendation No. 2: The NRCA should accept responsibility for correlating major roof problems and directing a coordinated program of research and investigation.
The NRCA deserves major recognition in this regard. It has funded research in a number of technical areas, including cellular plastic foams (phenolic foams, delamination, or crushing of polyurethane foam, aged conductance of foams, etc.).
The NRCA’s manuals set a standard for the industry, and most manufacturers have revised their manuals to agree with the NRCA details and specifications. NRCA’s Material Guides provide an index, in a standardized format, of virtually all products available today with referenced specifications, such as ASTM, FM, UL, etc.
NRCA’s Project Pinpoint was a way to highlight problems within generic types of roofing.
Recommendation No. 3 (for Technical Committees): Develop more accurate methods for determining proper location for expansion joints in both structure and roofing.
This is more complex than it first seems. Most roofing manuals recommend that construction joints be provided at not over 150 to 200 feet. Perhaps the recommendation that “joints shall be provided wherever the roof is likely to split” is a tongue-in-cheek guideline with a modicum of accuracy. While elastomeric roof membranes can be elongated by several hundred percent, new concerns, such as for membrane shrinkage and wind loads, still recommend anchorage at perimeters and roof penetrations.
Recommendation No. 4: Devise formulae or charts for more accurate selection of insulation.
In this age of computers, many programs are available to aid in this process. In addition, energy codes prescribe minimum thermal resistances. Focus at this point is more on issues of sustainability and recycling. The involvement of ASHRAE has led us to guidelines for thermal resistance by climactic region and type of construction, as well as dealing with the value of reflective roofs.
Recommendation No. 5: Investigate tilt deck construction to obtain the slope needed to eliminate water problems (ponding).
Virtually all roof insulation board systems are available in tapered form to increase slope to drain. Sprayed polyurethane foam can also provide enhanced slope. Metal roof systems are available to elevate roof areas at time of re-cover. Rules of thumb, such as providing a minimum slope of 0.25 inches per foot, have recently been revised to “provide positive slope.”
Recommendation No. 6: Determine when special means of venting are necessary.
Research by the U.S. Army Cold Regions Research and Engineering Laboratory (CRREL) has proven that roof vents are ineffective in removing moisture from roof envelopes. Today, there’s more interest in when and how to provide effective air barriers since air leakage from within a building can carry moisture (which results in condensation) and pressurize the roof system.
Recommendation No. 7 (for Manufacturers’ Committees): Develop foolproof materials and methods of installation to compensate for poor workmanship. An entirely new roof design based on new materials we do not now have might be the answer.
Single-ply materials can look with pride at this recommendation. Prefabricated roof panels, inside and outside corners, roof boots, weldable seams, termination bars, and the like are readily available. Evolution of these materials since the 1960s have seen improved primers, sealants, and seam tapes, as well as dedicated tools and fasteners.
Recommendation No. 8: Develop insulation that can be placed in plastic form (to eliminate joints), is unaffected by water, is impermeable, is strong enough to support roof traffic, and has other physical qualities making it suitable for installation over large areas and, of course, with a high insulating value.
(Sounds like a prescription for SPF, doesn't it?)
Recommendation No. 9: Construction funds should be adequate to obtain the roof required by the conditions. It’s equally important to provide adequate funds for subsequent inspections and maintenance.
Recent buzzwords, such as “sustainability,” imply that proper maintenance is provided and that the system be repairable. In many cases today, roof warranties suggest enhanced durability, but neglect and abuse will negate our best intentions.
This may be a special problem in advanced roofing systems, such as in conjunction with photovoltaics or vegetated roofs, where inspection or repair may be exceedingly difficult.
To a great extent, McCawley was able to address these issues in the nine chapters of his 1959 book. To his credit, as well as that of the National Academy of Sciences, all of the above issues have been addressed to some degree, although some issues, such as reflectivity, self-cleaning of roofs, seeking the perfect membrane, and thermal insulation, are still being addressed today.
If you’re lucky enough to have access to a copy of McCawley’s book, there’s a great deal more in it than just historical significance. It can provide insight into today’s systems and materials – even those not imaginable 70 years ago.
Unfortunately, despite their historical significance, McCawley’s books are no longer in circulation. Perhaps the MRCA or the NRCA should consider republishing McCawley’s book as a celebration of just how far we’ve come in the past 50 years, and where the roots or customs of many of today’s roofing systems originated. It would be a shame to let this gateway to the past be lost, especially since so many of our peers are fading away. (The NRCA is considering reissuing 100 Years of Roofing in America in 2011, and the Manual of Low-Slope Roof Systems [McGraw-Hill] was last updated in 2006.)