This article Reprinted from Western Roofing magazine, March/April 2007, Volume 30, number 2

 

“Pre-engineered” is the Buzz Word

Specialty Roof Deck Design is Becoming More of the Norm on Commercial Projects

by Richard K. Olson, technical director, TRI

 

(Editor’s Note: Richard K. Olson is technical director for the TRI. The association represents industry professionals involved in the manufacturing and installation of concrete and clay tile roofs in the U.S. and Canada, and works with national, state, and local building officials to develop installation techniques, codes, and standards for better roofing systems. Olson may be reached at rolson@tileroofing.org.)

 

 

Roof Systems are Becoming More Complex

                  With the increased demand to incorporate the latest in architecture design for commercial roofing, the design professional is venturing into uncharted waters in some respects. Over the last decade, there has been an explosion of new roofing materials that have entered the marketplace. There has also been a transition in demand to more long-term, durable roofing systems for all building designs. For the design professional and roofing contractor, this provides a unique challenge as many of the systems are relatively new options. Unlike the ease of installing tile on the conventional wood roof decks, there is not a wealth of knowledge in the field or even the design community to fully understand the proper installation requirements for some of the pre-engineered roof decks. Since many of these systems require the use of multiple components to properly install them, the roofing contractor and/or project manager will have to also understand the entire roof system as designed by the engineer or architect.

 

Pre-Engineered Systems

                  When we are dealing with these so-called multi-component systems, we are really referring to a “pre-engineered” roof system. In the case of concrete or clay roof tiles, these will occur when we talk about roof systems that have utilized concrete or metal decks below the tile. With commercial building design, this is becoming a more popular option these days. Even store fronts on commercial strip malls are now incorporating the use of the metal deck for a longer more durable roof decking material under tile.

                  The attachment of the tile, to provide the final perfect architectural look is easy once the batten systems are securely in place. In 2006, TRI released the Concrete and Clay Tile Installation Manual for Moderate Climate Regions. The guide addresses, in general terms, items of consideration for the use of tile on metal or concrete decks, but the drawings are not approved final “engineered” drawings for designers, as additional design specific details need to be added prior to release to the roofer. Also in the guide is a specific warning which states that they are for informational purposes only and not recognized under formal ICC-ES evaluation reports. As design professionals, you can utilize TRI’s information to help establish the additional information that you will need to include in your final drawings. This may require you to have additional understanding of the other components you are incorporating into the final system such as underlayments, insulation materials, fire barriers if required, and mechanical or adhesive tile fastening options.

 

Metal Deck

                  Installation of tile over metal decking for commercial buildings (warehouses) is becoming very popular in the southwestern United States. One of the leading questions TRI receives is how to best attach the tile, when an intermediate material is installed over the metal decking for insulating, moisture, or fire ratings. As a design professional, you will need to look at the design of the metal deck to determine how you will incorporate the tile batten fastening. Since there are numerous designs of metal deck thickness and corrugation, the placement of the fasteners will be critical if you are to provide proper uplift resistance and avoid long term leakage issues. Many of the insulating materials are components added to provide additional protection and are not designed to be the fastening material for the tiles directly. With use of these materials the fastening systems for the tile battens will have to reach the metal decking. By working with the underlayment material and metal deck manufacturers, the design professional can provide the proper mechanical fastening systems to keep the roof system properly installed.

                  As design professionals, you will need to consider the metal decking material, the underlayment systems (if any) and then the attachment of the tile battens. In the manual, TRI discusses the need for code-approved reinforced underlayment when draped directly over the metal deck with the use of GI metal battens fastened to the deck with code-approved fasteners. The designer will need to work with the metal deck manufacturer for the proper fastener sizing for the GI battens and proper screw sizes for attachment. When rigid roofing materials are installed over the metal deck and under our tile battens, we recommend plywood or other non-combustible substrate be used.

                  As an industry, we have recommended that the counter-batten system be used to provide the optimum support and ventilation to the roof system when installed. We show in our guide the option of having the underlayment installed under or draped over the vertical battens. Once the tile battens are in place, the tile installation will follow our normal requirements as outline in the moderate climate guide for fastening purposes and is easily accomplished. Our guide provides additional thoughts for utilizing drip edge, bird stops, and anti-ponding metals to provide the greatest long-term protection of the tile roof as a system.

 

Concrete Deck

                  Commonly used in the southeastern United States and in Mexico for lower pitched roofs, the concrete deck application is being used more often than in the past. As with metal roof deck design, the engineer must consider the proper method of tile attachment. In the TRI manual, we discuss the options of the counter batten system, which are similar to the options of metal decks. Also included is a section on self-adhering underlayment systems that allow tiles to be installed utilizing the adhesive foam-based fastening systems. Wire tie systems used on such roof decks are similarly considered pre-engineered roof systems, as the designer will have to specify the proper anchor wire, deck clip design, and the allowable spacing of fasteners up the roof slope to properly hold the tile in place.

 

Be Part of the Future, Expand Your Knowledge

                  To remain on the leading edge of roof system designs, design professionals must continually expand their expertise into the world of alternative decking materials such as metal and concrete roof deck construction, especially as those areas are growing in popularity for commercial construction. Concrete and clay tiles can provide a long-term, durable roofing material, but we need to have the “pre-engineered” roof options fully understood by design professionals to get the best practices in place in the roofing community. •••