Proper Installation of Drip and Rake Edges

Technical Bulletin #25

Current as of July 2021

When replacing shingles on a roof or constructing a new roof, it is important to give proper consideration to flashing details on the drip and rake edges.

When water runs down the roof, it pauses a moment before pouring off. When this occurs, the water may run back under the edge of the shingles often wetting the roof deck. This could cause the sheathing or fascias to rot after a few years. The easiest way to prevent this from happening is to install a drip edge at the eave and the rake.

Preformed drip edge can be made of aluminum, galvanized steel or copper. Though there are many shapes of drip edge available, it is important to use a product which does not hinder water from running off the roof.

Diagram - Installation of Drip and Rake Edges

At the eaves, apply metal drip edge over underlayment or directly to the deck.  At the rake, the drip edge is installed over the underlay.

The above figure shows the correct application of the drip edge. The drip edge should be nailed centered in the top surface every 8 to 10 inches.

The information contained in this bulletin is for general education and is not intended to replace advice from a qualified contractor or direction on usage/installation from the manufacturer. Consumers should be aware of the safety hazards associated with work on roofs and, before doing so themselves, should consider following CASMA s advice of using qualified contractors. This bulletin may be reproduced with permission on condition that it be reproduced in whole, unedited, with attribution of copyright to CASMA.