Inspecting Proper Flashing After A Storm Event
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.)
The recent weather trends have created tremendous demand for roof repair activity across the country. When called upon for evaluation of an existing roof after a storm, roofing professionals might include a closer focus on flashing as it relates to leak opportunities.
The number one concern mentioned in the inquiries received relate to improper roof penetrations. For concrete and clay roof tiles, we require both a deck and top flashing for all roof penetrations. Tile systems are designed with a natural airspace below the tiles that will increase the energy performance of the roof assembly. Tiles may be installed direct to deck or on a raised batten system that can increase the air flow.
On all tile installations, there must be a deck flashing in case water were to breach the tile. The use of a preformed deck flashing should be installed and woven into the underlayment system to ensure that any water that might get below a tile is prevented from entering the hole in the roof sheathing. Many of the calls we have received mentioned the application of caulking or roof mastic at the deck level. The concern here is there are different expansion rates of the materials involved, which can result in creating a gap around the vent hole over time.
For the top surface of the tiles, we recommend a flashing that will conform to the profile of the tile. This can be a soft flashing that will extend onto the tile a minimum of 4” on flat tile, and at least 1” past the crown on a profiled tile to prevent the water from entering.
The ability to properly direct water around a chimney requires the proper use of a backer/saddle or cricket application. The ability to properly flash will depend upon the width of the chimney and the tributary water upslope from the chimney to understand the potential amount of water that might occur in a storm event. If there are installations where debris accumulations can occur, the use of step flashing around the structure can reduce the opportunity for water to breach the system.
For tile installations, we recommend the use of a curb design around the opening that will provide the proper height of the skylight to the tile profile being installed. The curb should have all corners wrapped and sealed with a code-approved material before the tile is installed. The flashing method for a skylight will be as the chimney information above to properly direct water around the opening.
Proper attention to the use of counter flashings and exterior wall heights is important in the long-term performance of the roof assembly.
The head walls for profiled tile will need a weather blocking material to keep water from entering. The use of a roof-to-wall or apron flashing, with hem, is recommended in these areas.
The use of a proper valley metal is important in addressing the anticipated tributary water. For concrete and clay tiles, the use of a single or multi-rib metal flashing is an option. The IRC codes require a minimum of 11” from center of metal unless the local building officials have approved alternative designs. Installations of tile at valleys can be either open or closed valleys and the proper selection of an appropriate valley flashing is important. The use of the multi-rib metals can provide increased ability for water to stay directed downslope and help create a tile support. Be sure that tiles are properly supported by the flashing ribs, batten extenders, or other means to prevent water damming.