Installation of drip edge at the eaves, gables, and rakes is a common way to help mitigate the potential rotting of wood materials that can result from water getting underneath the edge of the shingles. This can happen if water flows back onto a roof deck or fascia. Drip edges provide efficient water shedding at a shingled roof’s eave, gable, and rake. The use of a drip edge also enhances the finished roof’s appearance, providing a clean, straight edge for all shingle courses.
The drip edge should be made of a corrosion-resistant material that extends a minimum of 2″ (51 mm) onto the roof sheathing and extends downward at least ¼” (6mm) below the roof sheathing. Though many drip edge profiles are available, it is important to use a product that does not hinder water from running off the roof. Drip edges should have an outward bent flange at the lowest edge (occasionally referred to as a “kickout”) to ensure water is directed away from running directly onto supporting wood materials.
As a general guideline, apply the drip edge underneath the underlayment along the eaves and over the underlayment on the rakes. (NOTE – When self-adhering underlayments are used at the eave, some shingle manufacturers and/or local building codes may permit the drip edge to be applied over the underlayment at the eave. In such cases, protection of the deck from water back-up due to ice dams forming below the eave (e.g. in the gutter), an initial 12” (300 mm) strip of self-adhering underlayment is installed before the drip edge installation. The lower edge of the strip should align with the expected lower edge of the drip edge, then adhered over the edge of the roof deck, and up the roof eave. After drip edge installation/fastening over this strip, the initial course of self-adhering underlayment is installed to overlap the drip edge as per usual practice. The net result is the drip edge is ‘sandwiched’ between two plies of underlayment at the eave, thereby providing protection from melted snow/ice from below and/or above the eave. Consult the manufacturer’s installation instructions). Fasten the drip edge to the deck with roofing nails at 8-10” (203-254 mm) on the center – do not nail into the vertical portion of any drip edge. A drip edge is strongly recommended on all shingled roofs and may be required by local building codes. If no drip edge is used, then all eave and rake shingle overhangs should extend 3/8″ – 1″ (10-25 mm). Refer to the shingle manufacturer’s installation requirements for specific installation guidelines.
The simplest drip edge shape is a 90-degree bent material (Figure 1), occasionally known as an L-shape. When using products with this profile, extending the starter course and field courses of shingles 1/4″ – 3/4″ (6-19 mm) beyond the drip edge at all eaves and rakes is recommended.
Other drip edge profiles, sometimes referred to as T- or D-shapes (Figure 2), incorporate a portion that extends outward from the roof edge before returning to match the roof structure. When using these products, shingles at the rake edge may be trimmed flush with the drip edge, while shingles at the eaves may extend up to 3/4″ (19 mm) or may be trimmed flush with the drip edge.
See ARMA’s Residential Asphalt Roofing Manual – Design and Application Methods for additional information. The manual is available for purchase on the ARMA website at www.asphaltroofing.org.
WARNING: Because it is dangerous to walk, climb or work on a roof, ARMA recommends that only trained professionals engage in such activity. If you choose to do so, exercise extreme care, comply with all government safety regulations, and follow all safety work practices, precautions and procedures, including but not limited to manufacturer’s instructions, labels, and warnings.
DISCLAIMER OF LIABILITY: This document was prepared by the Asphalt Roofing Manufacturers Association and is disseminated for informational purposes only. Nothing contained herein is intended to revoke or change the requirements or specifications of the individual roofing material manufacturers or local, state and federal building officials that have jurisdiction in your area. Any question, or inquiry, as to the requirements or specifications of a manufacturer, should be directed to the roofing manufacturer concerned. THE USER IS RESPONSIBLE FOR ASSURING COMPLIANCE WITH ALL APPLICABLE LAWS AND REGULATIONS.
Nothing contained herein shall be interpreted as a warranty by ARMA, either express or implied, including but not limited to the implied warranties of merchantability, fitness for a particular purpose or non-infringement. IN NO EVENT SHALL ARMA BE LIABLE FOR ANY DAMAGES WHATSOEVER, including special, indirect, consequential or incidental damages or damages for loss of profits, revenue, use or data, whether claimed in contract, tort or otherwise. Where exclusion of implied warranties is not allowed, ARMA’s liability shall be limited to the minimum scope and period permitted by law.
