One of the main functions of perimeter edge metal is to close off a roof system's perimeter. Because these areas are susceptible to water infiltration, a built-up or raised edge frequently is desired. This month's detail depicts a raised perimeter edge with metal flashing, also known as a fascia cap, for polymer-modified bitumen membrane roof systems.
To achieve a raised perimeter edge, a wood cant fastened to wood blocking typically is used. After the multiple-ply modified roof membrane system is in place, a backer ply is installed and extended over the roof edge below the blocking. An adhered membrane flashing sheet then is applied to the backer. For roof systems with factory-applied granule surfacing, the flashing can be installed between the base ply and granule-surfaced sheet. The flashing should be fastened about 8 inches on center.
Additional information about profiles, fastening and recommended minimum gauges for fascia metal and cleats can be found in BUR/MB Table 1 of The NRCA Roofing and Waterproofing Manual, Fifth Edition.
The metal fascia cap should be secured with gasketed fasteners spaced about 18 inches on center depending on wind zone and local conditions. NRCA recommends the cleat be fastened at about 6 inches on center with corrosion-resistant, barbed or screw-shank nails. The fasteners should be long enough to penetrate 1 1/4 inches into the wood nailers.
For fascia cap metal to comply with the International Building Code's 2003 or 2006 editions, it should be designed in accordance with ANSI/SPRI ES-1, "Wind Design Standard for Edge Systems Used with Low Slope Roofing Systems." NRCA maintains an approval listing with a code-approved testing agency, Intertek Testing Services/Warnock Hersey (ITS), Middleton, Wis., for the fascia cap profile (and others) shown in MB-2. NRCA member contractors can obtain a sublisting under NRCA's ITS approval listing.
Although a listing (or sublisting) by a code-approved testing agency is not specifically required for compliance with the code's new provisions, it does provide for independent, third-party verification of compliance with ANSI/SPRI ES-1.
If you are interested in being sublisted under NRCA's ITS approval listing, contact NRCA's Technical Services Section at (800) 323-9545.
Joan P. Crowe is an NRCA director of technical services.
Be the first to comment. Please log in to leave a comment.