Designing For a Longer Life
by Richard K. Olson, president & technical director, Tile Roofing Industry Alliance
(Editor’s Note: Richard K. Olson is president and technical director for the Tile Roofing Industry Alliance. The association represents industry professionals involved in the manufacturing and installation of concrete and clay tile roofs in the United States and Canada, and works with national, state, and local building officials to develop installation techniques, codes, and standards for better roofing systems. Olson can be reached at firstname.lastname@example.org.)
In steep-slope residential roofing, architects and design professionals are often asked by the building owner what will make a roof system last longer. The cost of a roof replacement may be the most expensive maintenance a homeowner will face during their lifetime. Depending upon the roof system, this may occur more than once during the lifetime of the building. Industry associations are often approached by consumers looking for education on ways to extend the life of their roof assembly. Design professionals will generally start with the discussion around what a proper roof assembly has as individual components. This will start with the substrate or sheathing that provides the structural support and ties the building truss system together.
When discussing code requirements, this is the perfect opportunity to provide options for potential upgrades that can help extend the life of the underlayment. For concrete and clay roof tiles, the codes require a minimum of an ASTM D226 Type II (No. 30) ASTM 4869 Type IV or approved equal. As a potential upgrade, recommend going with a single layer of an ASTM 40 pound, or two layers of the ASTM D226 Type II (No. 3). In certain areas where more severe weather may be a factor, the installation of a self-adhering option that meets ASTM D1970 might be the answer.
The ability to increase airflow of the roof assembly can also enhance the energy efficiencies of the roof assembly. For those products, like concrete and clay roof tiles that have above sheathing ventilation (ASV) that occurs naturally, the ability to increase the airflow through raising the tiles is an upgrade worth considering. While the building codes allow the tiles to be installed directly to the deck as a minimum, by upgrading to battens, counter battens, raised battens, or battens with greater airflow characteristics, you can significantly reduce the heat influx into the attic areas of a steep-slope application.
Proper flashing design is probably the greatest area of focus that can help extend the life of a roof system. If we can properly keep the water either on the roof cladding surface, or capture the water and daylight to the roof edge, we can avoid water from breaching the cladding systems. Part of this design discussion should include the use of step flashings, proper cricket designs, and roof-to-wall intersections that properly channel the anticipated tributary water that flows from upslope. Protecting these intersections is a fundamental foundation for any steep-slope roof system. The use of upgraded flashing materials in gauge or material might also be considered. For instance, many of the higher-end clay tile installations will consider copper flashings for a longer lifespan.
Roof penetrations probably create the greatest number of roof leaks from the lack of attention to long-term solutions. Too often we see the roof penetration sealed with a mastic that over time can expand and contract and allow water to breach the system. Upgrade options that utilize additional flashing can greatly expend the life of the roof assembly. For concrete and clay tile installations we have created penetration details that will require both a deck and top-of-tile flashing to reduce the opportunity of long-term issues. A penetration can occur during installation for pipe vents, stacks, or other accessories, but can also occur post install when solar or other devices are installed. In these installations, care must be taken to avoid cladding damage or leakage through lack of proper flashing. The Tile Roofing Industry Alliance always recommends that such installations have the input of a trained roofing professional.
Fastening to code provides a long-lasting roof assembly. In some areas where wind might be a factor, the option for additional fastening options might be considered. The codes will always provide the minimum requirements to meet the various design wind speeds, but upgrades might be considered for additional performance in some areas.
By maximizing upgrade options, the ability to significantly extend the life of a steep-slope roofing assembly for most claddings can be cost effective to the building owner. For more information on options, please consult with your component manufacturers to better understand costs, performance, and any restrictions that might need to be considered.