Drip edge is a no-brainer for asphalt roofs, and is now required by most building codes. But what about the use of drip edge on a metal roof? We asked CertainTeed (www.certainteed.com), which now makes a metal roofing system called Matterhorn, for their recommendations in this question-and-answer sequence:
Drip edge helps to keep eaves and rakes dry and free of water damage. Photo courtesy of CertainTeed
Q: I can understand why an asphalt roof needs drip edge, but why does a metal roof need drip edge?
A: A drip edge is not always required by local building codes, but installing a drip edge is a good idea—especially if the home is in an area that experiences a lot of wind-driven rain. This applies whether you are working with asphalt or metal because a drip edge allows water to fall away from the fascia. This helps keep areas like eaves and rakes dry and free of water damage. The rake is more visually exposed, so it’s easy to spot water damage to a rake without a drip edge. Furthermore, a drip edge helps seal any gaps that may exist between the roof deck and the fascia board and prevents unnecessary movement between the two.
Q: One might assume that a metal roof doesn’t need gutters, especially if you use drip edge—is that correct?
A: Many standing seam metal roofs are designed to divert water without the use of gutters. However, it’s incorrect to say all homes with metal roofs or a drip edge don’t need gutters. Panel metal roofing, such as CertainTeed’s Matterhorn product, installs much like asphalt roofing, so gutters may be desirable based on local weather patterns, roof pitch, the placement of hips and valleys, etc. The most important thing is that the system keeps water away from the fascia and even more importantly, the foundation. Drip edges can assist the gutters in diverting water away from important systems and structures.
Q: Does CertainTeed always include a drip edge with the Matterhorn system or does it need to be ordered separately? Is that standard with most competitors?
A: Matterhorn metal roofing systems come with a drip edge designed to be installed on up to 12/12 pitch without modification. On steeper roofs, the drip edge can be bent in a siding brake for easier installation and tighter fit. We can’t speak to it being a standard feature of other systems, but we believe the drip edge complements the look and functionality of our system.
Q: Some contractors bend their own metal. Are there any precautionary tips that should be provided to those who bend their own drip edge for use under the Matterhorn system?
A: The drip edge is designed to hold down the bottom of the first row of metal panels. When installing, be sure the drip edge is straight and square to the roof plane and does not follow any wave in the fascia (this may require a chalk line). Cut and bend drip edge trim on the outside to conform to the rake edge and the inner and outer gable. When adjoining sections of drip edge, cut the front nose on an angle to allow for a tight overlap and good fit. Sometimes the bottom hem will also need to be cut to make sure there is a tight fit. After the drip edge is completely installed on the eaves, install a synthetic, high-quality waterproofing shingle underlayment such as WinterGuard HT over the drip edge in accordance with local building codes to ensure a watertight system.
CertainTeed offers drip edge with its metal roofing system called Matterhorn, which offers the look of tile, shake, and slate. Photo courtesy of CertainTeed
Q: Drip edge looks like it would be fairly standard in how it is made. Are there differences in types of drip edge—quality or type of metal used, depth size, etc.?
A: Roof drip edges are generally sold in 10½’ lengths (and occasionally in smaller lengths). The length of the overhang typically is 2″ to 5″. Drip edges can be made from various plastics, vinyl, fiberglass, or corrosion-resistant metals. Aluminum, galvanized steel, and copper drip edges are the most common. Aluminum is often the metal of choice because it’s pliable, corrosion- resistant, and comes in a variety of colors. Steel is stronger, but it must be galvanized since drip edges are designed to come in contact with water. The three basic types of drip edges are the classic “L-shape” (called “L-style” or “Type-C”), the “T-shape” (“T-style” or “D-metal”), and the “Gutter Apron” or “F-style.” The T-shape keeps water further away from the fascia and is typically what Matterhorn systems utilize for eaves. Gutter aprons are typically used when installing new drip edges over existing shingles or rake edges.
Q: What mistakes do installers usually make? What are the correct installation methods?
A: Valleys, eave/drip edges, rakes, end wall, and side wall flashing must be installed before putting down the metal panels. For contractors who install asphalt, this can be counterintuitive, but it’s necessary when installing metal panels. When cutting panels to length, begin cutting from the top of the panel, cutting down toward the preformed bend at the bottom. This ensures the cleanest shear and keeps the rolled edge intact for optimal locking. For Matterhorn systems, always install panels from right to left, then bottom to top, beginning with the bottom right corner of the roof deck. When handling metal panels, carry the panels on their edge instead of resting flat to keep them from bending or warping in transport. Try to minimize foot traffic as much as possible and wear clean, soft soled, nonmarking shoes when walking on installed roof panels.
Q: Do some installers make the wrong tool selections? And what are the correct tools to use?
A: The tools for installing metal roofing, including drip edges, are pretty straightforward. Your most basic tools will be a cordless driver to drill down components, tin snips and a hand seamer to cut and manipulate the metal, a chalk line to ensure accuracy, sheet metal gloves for protection, and a foam pad for safety. A sheet metal brake, power shears, table saw, or circular saw can make installation easier but are not necessarily required. With a modest tool investment, a skilled contractor can accomplish most metal roofing installations.