Mark Zehnal, CPRC, FRSA Director of Technical Services
At the January FRSA Board and Committee meetings in St. Augustine, the Codes and Regulatory Compliance Committee received a research update on fastener corrosion. Associate Professor of Civil Engineering Kurtis Gurley, PhD from the University of Florida Engineering School of Sustainable Infrastructure & Environment provided a PowerPoint presentation on the Florida Building Commission (FBC)-sponsored fastener corrosion research project. Dr. Gurley was accompanied by his research associate Brandon Czarzasty. Dr. Gurley’s presentation included the progress of this project since its inception.
In 2013, the FBC approved funding for a research project proposed by the FBC Roofing Technical Advisory Committee (TAC) addressing fastener corrosion. The idea was to develop a survey for roofing contractors and other professionals to determine if there was actually a fastener corrosion problem in Florida. Dr. Gurley worked with FRSA and the Roofing TAC to develop the survey questionnaire. The questionnaire, which was administered by phone, contained 21 base “yes” or “no” and multiple choice questions with an additional 31 sub-questions of the same type that expanded on the base questions. The phone survey was conducted between May 13-30, 2014 taking, on average, 10.5 minutes to complete. The survey was completed by 385 participants which translated into a 25.7 percent response rate out of the original 1,500 persons randomly selected from a 4,000-person list of Florida licensed roofing contractors. The survey results indicated that fastener corrosion is commonly observed, especially in coastal areas.
The survey results also indicated that fasteners with electrogalvanized coating were more likely to experience corrosion. The survey information was reported in ROOFING FLORIDA Magazine, July 2014.
Due to the success of the survey results the Roofing TAC decided to request additional funding to continue the research into the corrosion of fasteners. This continued research would be needed to verify the results the survey had established and hopefully provide answers to correct the problem. The Roofing TAC’s concerns were centered around where the fasteners came from, if any code compliance standards were used and listed on packages, and would the standardization of Testing Application Standard (TAS) 114 Appendix E for all roofing fasteners be a possible solution.
The FBC funding was approved for the testing of roofing nails in accordance with the TAS 114 Appendix E Standard. Testing would take place at the University of Florida. The purchase of a Cyclic Corrosion Tester manufactured by Q-LAB was included in the proposal by the University of Florida.
The Roofing TAC also requested that some fasteners be tested driven into wood, through shingles and metal flashing in addition to individual fasteners tested right out of the box. Fasteners were to be hand- and pneumatically-driven.
Time was running out to test any samples due to the length of time it took to purchase and install the Q-Lab equipment. It became necessary to select at least one fastener type to focus on in an effort to have viable results to provide to the FBC. Dr. Gurley consulted with FRSA about the priority of fasteners to be tested and it was determined that the 1-1/4 inch coil nail used for most dry-ins, flashing, and shingle installations would be the best candidate. The University of Florida purchased electrogalvanized 1-1/4-inch coil nails from three different manufacturers.
TAS 114 Appendix E is an acetic acid-salt spray test, or what some call a fog test. Each sample was to be tested through 140 cycles. One cycle involved one-hour fog and one-hour dry-off and then the cycle starts again and will run without or with minimal interruption over a twelve-day period of time. According to TAS 114 Appendix E, failure is when any test specimen exhibits corrosion on an area in excess of 5 percent of its total surface area. Dr. Gurley used a different approach in determining the results of the 140 cycles. He felt the purpose of this study was to investigate the relative performance of electrogalvanized fasteners in both
out-of-the-box and multiple installed conditions and that this
required a finer gradation of performance than pass/fail could provide. An integer scale of 1 – 8 was created to classify the degree of corrosion observed on the fasteners:
1. No corrosion observed
2. Edge corrosion only
3. Light partial surface corrosion
4. Light full surface corrosion
5. Partial heavy surface corrosion
6. Partial heavy and partial light full surface corrosion
7. Heavy full surface corrosion without scaling, and
8. Heavy full surface corrosion with scaling.
So a sample that passes the TAS 114 Appendix E pass/fail criterion corresponds with scores of 1, 2 or 3. However, 3 could either be a failure or a pass. Additionally, the TAS 114 Appendix E applies to both the head and shaft. Thus, a specimen with a head score of 1 or 2 and a shaft score of 4 would be considered a failed specimen.
In August of 2015, for the third consecutive year, the FBC approved funding for increased testing of fasteners during 2015-2016. Additional types of roofing fasteners were to be purchased at local roofing distributors or big box stores such as galvanized nails,
roof tile fasteners, and exposed metal fasteners with different corrosion coatings for additional testing. There will be an interim report submitted to the Roofing TAC in early March 2016.
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