Consultant's Corner: Keeping Up With Roofing Industry Changes

 

 

 

 

 

 

 

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By Ronnie J. Erdman, Terracon Consultants, Inc.

 

 

This is not my father’s roof system. In his day he would have heated up coal tar pitch and used it to install a simplistic four- or five-ply built-up roof, embedding the slag in a flood coat of coal tar before moving on to the next project. Back then, not much emphasis was placed on roofing assembly attachment. However, roof system technology has changed dramatically over the years, even since my introduction to the roofing industry more than twenty years ago. With the development of new installation techniques, the addition of elastomeric and polymeric modifiers to traditional roofing materials, and new single-ply thermoplastic technology, we have entered a new millennium of roofing. For building owners and design professionals alike, keeping up with all the changes  can be an overwhelming task. All the same, keeping up can help save time and money. So, read on. This brief “101” is designed to provide some important insights and lead you to additional helpful information.

 

FMG Loss Prevention Data Sheet 1-29

Some major changes in the industry such as the recenlty updated Factory Mutual Global (FMG) Loss Prevention Data Sheet 1-29 “Roof Deck Securement and Above-Deck Roof Components” are causing needless expense to uninformed building owners and managers. As a result of the new FMG Loss Prevention Data Sheet 1-29, most roofing material manufacturers can no longer meet the FMG requirements for any “fully adhered” roofing system over steel decks; including single-ply, fully mopped built-up and modified systems, torch applied, cold process and self adhered membrane systems. FMG 1-29 as well as the American Society of Civil Engineers’ “Design Guidelines for Wind Loads on Buildings” (ASCE-7) are based on the same basic wind speed maps (Fig. 1). However, over 90% of the commercial buildings in the United States are not FMG insured, so why base roofing installation on FMG recommendations? In the past it has been commonplace for roof system designers to utilize the language associated with FMG I-90 requirements for the simple reason that it was the most stringent set of requirements available. 

 

Prior to January 2006, FMG 1-29 recommended increasing the fastening of insulation from the field for fully adhered roofing systems on steel decks an additional 50% at the perimeter and 75% at corners. After January 2006, FMG 1-29 states that for the field of the membrane to meet an I-90 rating (and in most cases that is only required by the designer or installer and not for any realistic reasoning), the assembly must pass FMG’s testing for the highest pressure at the corners. For the FMG 1-29 certification that is a minimum of 225 pounds per square foot (psf) of uplift resistance. For an I-75 rating an increase of 100% fasteners versus field fasteners at the corners is now required. The expense associated with this additional fastening can add thousands of dollars to the cost of a roof system installation.

 

ASCE-7

The design community needs to be cognizant of these added costs, which means being fiscally responsible to their clients and providing them with the best roofing solutions at the lowest possible cost. With this in mind, if the building is not an FMG insured structure, the designer should take the time to perform the proper calculations to determine the design wind uplift pressure required for the specific building in question. Most building codes such as the International Building Code (IBC) reference the ASCE Standard 7 for comprehensive roofing, and the codes require that enhanced fastening at the perimeter and corners follow the ASCE standard. The ASCE-7 roof uplift design pressure is based on the building height, location, importance factor of the building, and surrounding ground roughness along with appropriate safety factors. Using these factors, the design uplift pressure is determined for the field of the roof and subsequently the number of fasteners required at the field, perimeters and corners. Most major roofing manufacturers are more than happy to assist in this analysis if called upon, and some even have the wind speed calculator right on their Web site.

 

Windstorm Insurance Eligibility

To be eligible for windstorm insurance or re-insurance within the 14 coastal counties in Texas (and including the very tip of Harris County), the new roof or re-roof must be certified as compliant with the Texas Department of Insurance’s (TDI) guidelines for windstorm resistant construction (which include the requirements of ASCE-7) by a professional engineer who is certified by the TDI. It is not a requirement that the roof comply with FMG 1-29. The Texas Windstorm Insurance Association (TWIA) is a funding pool funded and utilized by insurance companies for re-insurance to distribute their risk. Any structure built after 1998 must meet the TWIA minimum requirements for wind uplift. The project must also be inspected by a TDI “Certified Windstorm Engineer” for compliance to obtain the TDI “Certificate of Compliance” that is required within its special wind zone. For additional information on this topic you can go to www.tdi.state.tx.us/wind/index.html.  Make sure you know where your project is located on the wind zone map before you start the roofing or re-roofing process.

 

Though the roofing industry is constantly changing, today more than ever, a well educated, well informed approach to roof design and installation is absolutely critical to get the most for your investment. If your building is not an FMG insured structure and you do not want to spend the additional monies to meet their wind uplift requirements, talk to a roofing design professional prior to the design formulation process. In the end, you will be happy that you did and most importantly you will be able to utilize the cost savings for other desired projects.

 

 

Mr. Ronnie J. Erdman is Terracon – Houston’s senior roofing/waterproofing consultant. He has over 20 years of professional experience in roofing & waterproofing forensic investigations and contracting. Mr. Erdman holds certifications from Roof Consultants Institute (Roof Technology I & II), Rooftop Quality Assurance and the American Institute of Architects.  He is also affiliated with the Constructions Specification Institute and the American Society for Testing Materials National.