Letters

In the article "The hurricanes of 2004," September issue, page 22, Thomas L. Smith, president of TLSmith Consulting Inc., Rockton, Ill., provides some good insight into the performance of roofing materials during the 2004 hurricane season. However, the Tile Roofing Institute (TRI) must take exception to some of the comments in the article.

Based on viewing only a few tile roofs, Smith says tiles did not "perform as predicted" and the industry's installation manual predicted performance that was not achieved. These statements infer uplift values used by the industry are invalid. In fact, the fastening tables included in the third edition of the Concrete and Clay Roof Tile Installation Manual, published by the Florida Roofing, Sheet Metal and Air Conditioning Contractors Association (FRSA) Inc. and TRI, are based on extensive testing, including full-scale wind tunnel testing in winds exceeding 125 mph (56 m/sec) and static uplift testing in winds more than 150 mph (67 m/sec). The tables provide tested resistance values for mechanical and adhesive-set systems.

TRI sent teams in 2004 to evaluate the performance of tile roof installations in Florida and found roofs that were properly installed according to the manual did perform well. We agree there was improper workmanship in many of the failed roofs installed after the 1997 code changes.

Furthermore, the article does not provide enough details to support its conclusions about performance. There are many aspects to consider when properly evaluating a roof assembly for wind damage, including wind speed, gust speed, wind direction, exposure, roof height, roof slope, proximity to surrounding buildings, down drafts and tornados.

In the case of the mechanically fastened tile roof shown in the article, the size, length and number of fasteners would need to be verified in addition to whether they were installed correctly to allow for the greatest design uplift resistance. The TRI field team observed damage similar to that in the photo. In many of these cases, the damage was caused because only every third tile had fasteners, leading to a corner/eave course blow-off. It's also possible the blow-off of the hip and ridge tiles that were installed in mortar without a nailer board may have caused much of the damage to the field tiles shown in the photo.

TRI's field observations are consistent with Smith's in terms of a lack of performance of hip and ridge roof tiles. As an industry, we have addressed this problem. TRI, in conjunction with FRSA, performed an in-depth review of field data from the 2004 storms. As a result, the groups drafted a 30-page detailed document about hip and ridge tile attachment that includes recommendations for mechanical, adhesive-set and mortar-set systems. The guidelines were adopted into the Florida Building Code Nov. 1.

TRI and FRSA continue to review data from current wind events to further improve standards. We are confident concrete and clay roof tiles, when properly installed to industry recommendations, will perform at the wind speeds indicated in our published guide.

Rick Olson
TRI
Chicago

Following is Smith's response to the article:

Olson infers the observations were mine. I did author the article that gave an overview of Federal Emergency Management Agency (FEMA) reports 488 and 489, and I was a member of the FEMA teams. However, the observations and data analysis in the reports were those of the team rather than any individual.

Collectively, the reports have 28 pages (including 32 photographs) about tile roofs. The reports state varied performance levels were observed, ranging from no damage to substantial damage.

Further information regarding those roofs that did not perform as predicted by the Concrete and Clay Tile Installation Manual is provided in the reports. The uplift loads in the manual were not questioned. However, the report recommends FRSA and TRI re-evaluate the tables in the manual. The tables are based on static testing, but tiles are dynamically loaded during a hurricane. Dynamic loading may cause fastener jacking or nail hole enlargement. If either of these events occurs, the resistance predicted by static testing may not be achieved.

I'm pleased FRSA and TRI developed new criteria for hip and ridge tile attachment. Poor performance of hip and ridge tiles during Hurricane Andrew was documented, but I'm not aware of any industry response to this issue until the 2004 hurricanes once again demonstrated this vulnerability.

I encourage readers to download FEMA reports from www.fema.gov/fima/mat/mat_rprts.shtm and review Hurricane Recovery Advisory No. 3 (located in the appendix of each report).