Technical Viewpoint: Metal Roofing Specifications
And along came metal.
Anyone can see that metal roof panels can’t leak. They are available in varied colors, can be rolled to conform to aesthetically pleasing radii, and can be installed on both low- and steep-sloped roofs. And, after all, the old terne metal roofs of the turn of the century lasted “forever” and “never” leaked (which is why so many have been repeatedly covered with asphalt and numerous other coatings). And metal roofs come with long-term “warranties” issued either by the paint supplier, the “manufacturer” of the panels, or by the “broker” who buys and resells metal roof system panels and components. Today’s metal roof systems are obviously the roofs of choice to eliminate all prior roof system problems!
Architects understand even less about metal roof systems than they did about sheet membrane or built-up roofing systems, and many of the problems associated with metal roof assemblies stem from the design (or lack thereof) of the metal roof system. Designers are content to specify only that the contractor “shall follow the manufacturer’s installation recommendations.”
Architectural specifications for metal roof systems are very often contradictory. They stipulate both FM (Factory Mutual System) and UL (Underwriter’s Laboratories) classifications, which may be similar, but not identical and may contain irreconcilable differences in construction. They make reference to both SMACNA (Sheet Metal Air Conditioning Contractors National Association) and the “manufacturer’s” recommendations, which in most instances, may not be remotely similar. They also include designs that do not match the roof assembly configuration that was tested for wind uplift or fire properties, which will be in violation of local or model building codes, in many cases. It is incumbent on the roofing contractor to define the discrepancies in specifications and either get them resolved or take exception to the conditions prior to commencing installation. Failure to do so may be hazardous to the business health of the contractor.
For instance: the “design” specifications stipulate that the completed roof assembly have a UL wind classification of UL-90, or 90 psf uplift. The roof assembly installed to comply with these criteria must be constructed exactly as tested by UL when the wind uplift classification was determined. Pay particular attention to the minimum type and density requirements for foam insulation over which the metal roof system is to be installed (understanding that commercially available isocyanurate foam insulations will rarely approach 2 pcf density) and special requirements for attachment devices. UL Construction Numbers listed in the UL “Roofing Materials & Systems” Directory must be cross-referenced to the specifier's “roof section” to determine whether or not the “test construction” and the “specified construction” are essentially identical. If not, the finished product will not have the wind uplift classification included in the performance criteria of the specifications, and the contractor may be in breach of contract for not providing a system that meets the performance criteria of the design specifications (UL-90).
Such small discrepancies can lead to holding of retainage or calling of the Performance Bond (or worse, a lawsuit for non-compliance with specifications) and can be very expensive to correct. In most cases, removal and replacement of the entire metal roof system is the only way that the system may be brought into compliance with the design criteria of the specifications. At the very least in these types of situations, a compromise must be reached by all parties, which is usually not “good” for anyone and causes a lot of hard feelings.
If the specifications call for both UL and FMRC (Factory Mutual Research Corp.) classification, be aware that the testing methods employed by these two organizations may be different and that UL tested constructions may not be similar to FMRC tested constructions. Which one will you choose? You can’t build both — the constructions may be mutually exclusive and neither may be acceptable in the end. The designer or the owner must choose between one or the other testing agency requirements, preferably prior to commencement of construction on the roof system.
It is also important that the system be tested and listed/approved by the specified agency. Some suppliers of metal roof systems have their systems tested at independent testing labs or perform the wind or fire tests themselves to save the costs association with UL or FMRC testing and evaluation. Just because a metal roof system is represented by the supplier as having passed the UL 90 test does not mean that the system was tested and listed by UL — a seemingly small point, but another major stumbling block in complying with specifications which stipulate that the system be UL tested and listed. It should not be construed that the untested assembly is necessarily inferior to a tested assembly, only that the formalities have not been complied with and that untested assemblies may not meet the performance criteria of the project specifications.
“Submittal” drawings from suppliers or contractors often do not match “shop drawings” for specific projects, and discrepancies go “unnoticed.”
Manufacturer’s “recommended” details often come with a caveat that “XYZ Mfg. Co. shall be held harmless from any and all claims arising from a lack of watertightness as a result of following these recommended details.”
The installation of the metal roof system is subcontracted to a non-approved applicator/erector (if, in fact, approved applications are recognized by the supplier of metal roof system components), so the warranty may be void when problems do occur.
Nobody pays attention to these types of details until the lawyers draw them to someone’s attention.
“Warranties” on most metal roof systems do not include “watertightness” of the finished assembly; only the “finish” on the panels on which the warranty may be voided by exposure to coastal areas, animal feces (be sure the local animal population is potty-trained before accepting this warranty) or acid environments (try to find one outside Montana, and even some areas there may be questionable).
Roofing contractors (and architects/owners) should understand that when a roofing contractor purchases metal coil stock from a steel supplier (who may have tested some roof systems and outwardly appears to be a “manufacturer”) to roll metal roof panels at the job site, that they, in essence, become the “manufacturer” of the metal roofing system and may be held for the term of the specified “manufacturer’s warranty” in the strict sense of the contract. The purveyor of metal materials from which the roof system components are field-fabricated will assume no responsibility for issuance of a warranty on the roof system other than, perhaps, a warranty on the paint/finish on the coil stock or panel material.
Fully understand the implications of the warranty requirement included in the bid documents, and either select a warrantable manufacturer’s metal roof system to comply with the contract documents, or be willing to assume the responsibility for any long-term warranties required by the designer. Designers must understand that no conventional “manufacturer’s guaranty” may be available on field-fabricated metal roof systems.
In response to problems (perceived or real) with low-slope roofing membranes, the states of North Carolina and Maryland (and maybe some others) have mandated that minimum slopes on the state’s school roofs shall be 2 inches or 2 1/2 inches in 12 inch, too steep for low-slope roofing membranes, but not sufficient slope for shingle/tile/slate coverings. The major problem with school roofs — no matter what the slope — has been, and will continue to be, the low-bid and the lowest cost roof system proposed by the lowest bidder. And the folks who made these rules haven’t figured out that “fixes” for metal roof systems that are not properly detailed or installed are few and far between without major restoration — and the costs of restoration of improperly detailed/installed metal roof systems are high. Construction attorneys should begin to understand metal roof systems . . . they will be their future job security.
When metal roof systems are specified to be installed, it is even more important that the designer/owner understand the “warranty” to be issued on completion of the project. Most owners anticipate that a “warranty” on their new metal roof system will provide the same “leak-free” clause that is common in other roof system guarantees. They will be “mad as hell” when they learn that the only thing covered by the metal roof system warranty is the paint finish on the roof panels — and that is covered only if their roof is constructed inland and away from birds and other critters.
Recovery of existing metal roof systems may be a major problem if it is necessary to comply with UL or FMRC listings/approvals. Similarly, removal and replacement of metal roof panels may not meet some listing/approval requirements.
There are some very technically solid metal roof systems available from very responsible and responsive manufacturers of metal roof systems today. And then there are simply brokers of metal roof system components or purveyors of metal coil stock from which panels may be field-formed, who detach themselves completely from the end product either with very limited warranties or with general disclaimers about the components and systems sold by them. Sound familiar? The metal roof system industry is not much different from any other segment of the roofing industry – there are those who try hard to provide tested and proven roof systems and materials, and those who simply don’t care if the system/material works or not, as long as they collect their money.
It is, indeed, caveat emptor!
In all, it’s been another interesting year in Black Rock. Change is inevitable and often for the better, even if there is much consternation preceding the final outcome. It is important to continue development efforts for the more cost-effective waterproofing and roofing systems; it’s just as important not to get caught in the mire between “new” and “proven.”