Florida Roofing - May 2021

Page 26

Florida May Have a Flaw in its Roofing Code Armor Mike Silvers, CPRC, Owner of Silvers Systems Inc. and FRSA Technical Director

During the FRSA-TRI Florida High Wind Concrete and Clay Tile Manual Review Committee meetings that started in 2018 and ran into 2020, an issue that was widely discussed concerned the load path required for roof coverings to resist uplift pressures and the increases in those pressures that ASCE 7-16 would create. This topic applied to almost all roof systems, not just tile roofs which were our primary focus. Meeting the requirements for uplift resistance is more complex for tile than most other systems. There are many reasons for this, but among those are the need to resist both uplift pressures for underlayment, as well as for hip and ridge or trim tile in pounds per square foot while meeting the aerodynamic uplift moment resistance required for the tile itself. This is further complicated as many of the components are manufactured by different companies. In many cases, the tile is adhered with foam adhesive or, in rare instances, with mortar to the underlayment which must be adhered or fastened to the roof deck to complete the roof system load path. Many of the prescriptive methods previously used to adhere tile were based on information obtained for what is commonly referred to as a 30/90 hot mop. Much of this information was adopted and transferred when self-adhering membranes came on the scene. But as self-adhering membranes’ popularity grew, it became obvious that the adhesives performed differently than hot asphalt. One difference was demonstrated as selfadhering membranes were introduced for low slope roofs, where meeting uplift pressure resistance 26


requirements were more universally understood and expected. Installing self-adhering membranes to standard #30 felt or other standard base sheets would yield very low uplift resistance when tested. That led to the introduction of specially designed base sheets that allowed for better adhesion as well as improved nail pull through test results. For some of us, it seemed counterintuitive that we needed special base sheet for adhesion of mid ply and cap sheets on low slope roofs but didn’t need them when we were adhering tile to those same materials on steep slope roofs. The information available from several manufacturers who had tested for product approval using an ASTM D226 #30 with self-adhering underlayments resulted in very low resistance numbers that were not equal to those required for most roofs in Florida. An important decision was eventually made by the FRSA-TRI Manual Review Committee that in order for the manual to comply with ASCE 7, tile underlayments had to meet the uplift pressures and this would be the approach reflected in the manual. It led to separating how the manual dealt with the hot mopped and self-adhered underlayments. Hot mopped systems have prescriptive methods included in the manual. Self-adhering membranes use the manufacturer’s product approvals – a conservative approach arrived at with an abundance of caution. This left Florida’s roofing contractors and tile manufacturers concerned about the possible afore mentioned flaw. The Test Protocols for High-Velocity Hurricane Zones (HVHZ) included in the Florida Building Code, and in particular, Roofing Application