Letters

Professional Roofing welcomes letters to the editor. Views expressed in "Letters" are not necessarily those of NRCA. Letters must be signed and include a return address and telephone number. Professional Roofing reserves the right to edit letters for clarity and length. Send letters to Ambika Puniani, Editor, Professional Roofing, 10255 W. Higgins Road, Suite 600, Rosemont, IL 60018-5607; fax (847) 299-1183; or e-mail apuniani@nrca.net.

Retrofit metal concerns

I read with great interest the September article "The rise of retrofit metal," page 32. The authors, David W. Boozer, an area sales manager for Architectural Metal Systems, Eufaula, Ala., and Allen Lancaster, president of Metalcrafts Inc., Savannah, Ga., present many good points about retrofitting metal roof systems onto an existing roof structure. However, the published details present an unacceptable method of supporting a new roof system.

Do not use these details. Placing a base clip/bottom Z on top of the existing roof system and not directly onto the building's structural components is misleading. The concept "a picture is worth a thousand words" in these graphic descriptions can lead to roof system failure.

The article's content needs to be properly displayed in the details presented. Details are the greatest provider of information for those involved in the construction trade. It is these images that so many roofing workers, maintenance personnel and roofing contractors use to show building owners the way to install roof systems. These major flaws should not be allowed in such an important magazine as Professional Roofing. These details are far from professional.

Terry Blake
RBS Design Group
Owensboro, Ky.

Following is Boozer's and Lancaster's reply to the letter:

"Based on your letter, it appears there is disagreement about installing a metal retrofit framing system over an existing roof assembly. That opinion exists in the marketplace. However, it is our opinion that a metal retrofit framing system can be installed over an existing roof assembly and perform properly.

"As we have stressed, the base anchoring of metal retrofit framing systems is important. The existing insulation and roof system can be used as support of a base clip and/or base runner if its ability to accept compressive loads is adequate. We acknowledged this in the article by stating, 'An existing insulation system supporting an existing roof covering must be checked for compressive loading.' We also noted wet insulation must be dried or removed and replacement insulation must withstand a new roof system's dead and live loads.

"The details were intended to illustrate the various components and their location in a roof assembly. The details were in no way intended to provide any specific design method and should not be used in this manner.

"Metal retrofit framing is a complex, detailed system that is job-specific and requires engineering services. There are numerous ways to provide anchorage and support, some of which we have tried to identify with new methods being developed all the time."

Following is Mark S. Graham's, NRCA's associate executive director of technical services, reply:

"The photographs and details in the article were provided by Architectural Metal Systems and do not necessarily represent the recommendations of NRCA.

"NRCA's recommendations concerning retrofit structural metal panel roof systems are provided in the Reroofing section of The NRCA Roofing and Waterproofing Manual, Fifth Edition.

"On page 721, the following statement directly addresses this issue: ‘Framing systems must be engineered to transfer roof loading to the existing structural members supporting the existing roof deck.'

"The text goes on to say: ‘In some cases, metal roof framing is attached by an individual base plate that is located directly over an existing structural member. It is important to ensure that the new framing rests on a surface that is rigid enough to support it. The existing roof system is removed where the vertical framing members occur so the new framing bears directly on the existing structural members.'"

Questions about laminate shingles

Thank you for the article about laminated shingles in the August issue ("Are laminates tolerant?" page 30, by Mark S. Graham, NRCA's associate executive director of technical services).

My 40-year practice in design, renovation, construction management and building inspection has exposed me to many roof system problems. However, I find the second to last paragraph in the article rather weak from the standpoint of a building owner's expectations. To quote Graham, "Also, building owners, project designers and consultants should have realistic expectations of the application parameters associated with laminated asphalt shingle assemblies."

Is Graham saying building owners should know manufacturers are creating a problem product for which owners pay a premium price? Or is he saying application contractors have to be watched to verify every nail precisely is placed? Or building owners should not expect [to have] a 30-year roof system without some laminated surface pieces slipping down?

I have reported about improper application and slipping of the laminated top piece down mansard facades. Would Graham please clarify his statement?

Donald V. Cohen, P.E.
Thiensville, Wis.

Following is Graham's response to the letter:

"Thank you for your letter.

"What I am saying is that except for Sample 7A, the installation tolerances provided by the design and manufacturing of the laminated asphalt shingles included in this study are not adequate to provide for proper application by experienced roofing contractors during typical rooftop application conditions. Building owners, project designers and consultants should be aware of that when they purchase, specify or inspect roof systems with these laminated asphalt shingle products."

A reader shares his differing views

My letter is regarding two articles by NRCA's Associate Executive Director of Technical Services Mark S. Graham: "Asphalt shingle application tolerances," March 2000 issue, page 106, and "("Are laminates tolerant?" August issue, page 30.

As an independent [roof] consultant, designer and quality-assurance monitor who has installed and inspected many shingle roof systems, I respectfully disagree with Graham's premise that "it is not possible to achieve consistent nail placement according to manufacturer's exacting recommendations."

Although occasional manufacturing errors in marking target areas are possible—perhaps inevitable—responsible contractors will not use that as an excuse for careless installation. If a discrepancy is found in the marking of a target area, a contractor should notify the shingle manufacturer to rectify the condition before shingles are installed. Installation should be done properly, and NRCA is remiss in promoting the idea that proper installation is somehow too high a standard for roofing contractors to consistently achieve.

Roofing professionals acknowledge that shingle (laminated or three-tab) fastener target areas are minimal and manufacturing errors are possible, which result in limited targeted fastening areas. Wouldn't common sense dictate that a contractor check the product he is installing and determine the correct fastener placement location? If a discrepancy is found, a contractor should notify his supplier or the shingle manufacturer and document the condition.

In continually reviewing work in progress and analyzing completed work, substandard fastening is a serious problem with many steep-slope roofing projects. For example, fasteners are placed inches away from target areas or are missing, underdriven or overdriven. Why should a manufacturer cover such applications when it provides application specifications indicating correct fastener placement? It also has been my experience that when there is substandard fastening, other installation requirements also are neglected. On the other hand, I regularly observe many contractors installing shingles by consistently placing fasteners properly.

In the March 2000 issue, Graham states "experienced asphalt shingle installers generally agree it is not possible to achieve consistent nail placement according to manufacturer's recommendations." This is nonsense. Who are these "experienced" asphalt shingle applicators? I note two types of contractors: those concerned with production only (my guess is these are the "experienced" applicators) and those concerned with quality roof system construction.

A larger target area for fastener placement seemingly would alleviate many problems currently encountered as a result of substandard fastener placement. But will a larger fastener target area allow a mechanic, who is paid by the square, to take time to review or seek a manufacturer's installation data? Will contractors currently experiencing problems caused by incorrectly placed fasteners properly train their field workers?

My answer to these questions is "no." The solution to the largest part of this dilemma is pride in workmanship. If a contractor and his mechanics have this quality, directions are easy to find and follow.

Letters

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