How Far Should Shingles Overhang a Drip Edge?
A drip edge is a preformed metal flashing applied to the edge of the roof deck that serves three purposes:
Protects the edges of a roof deck during wind-driven rainstorms
Directs water into the gutters
Provides a clean look to the edge of a roof
If a drip edge is not installed under shingles, water runs down the surface of the wood rather than away from it, causing the rake and fascia boards to rot and for the wood to become extremely dirty. Installing a drip edge is important to the overall health of the roof and frame structure, but having the shingles applied correctly over the drip edge is equally crucial.
What is the best shingle overhang, and why is it important? Let’s start with drip edge materials and shapes.
Drip Edge Materials
Drip edge is manufactured from both metal and plastic. The most common material is light gauge aluminum. Aluminum won’t rust or corrode and doesn’t react negatively to the nails that are typically used in residential shingle installations.
Another popular material is galvanized steel. Since the drip edge is going to come in contact with moisture every time it rains, the steel needs to be galvanized or painted in order to prevent rust.(Most steel drip edges will need to be painted regardless, so they will match the fascia board for a more cohesive home design.)
Copper is also used as a drip edge and provides a one-of-a-kind look. It is more expensive than either steel or aluminum and is typically found on homes that have copper or copper-colored roofs.
You will occasionally hear the term “drip edge” applied to plastic and vinyl, but these products are generally used around windows and doors as flashing. They are not a good alternative for use under shingles.
Drip Edge Shapes
There are three basic drip edge profiles or shapes used by today’s roofing contractors:
Type C (or L-Style): This profile is used most often in re-roofing projects, and it can be known as Type C or L-Style. It is formed in the shape of a “L” and will fit over existing roofing materials. It may have an additional 45-degree bend at the bottom to ensure that water drips away from the fascia into the gutter.
- Type D or T: This is the most common profile used in residential construction. It is formed with a 90-degree angle in the main section and a 45-degree angle at the bottom. It is intended for new construction and should be nailed directly to the roof deck before ice and water shield or underlayments are installed.
Type F: Shaped like Type D, this drip edge has an extended leg that runs down the fascia. It is sometimes used in re-roofing projects where the extra length is necessary when installing over an existing roof.
Installing Shingles Without a Drip Edge
There are roofing companies that will install shingles without using a drip edge. That may meet building code in some areas, but it does not offer the best protection for the roof deck or the shingles. A drip edge will keep the shingles from bending over into the gutter and will provide edge protection on the rake or angled portion of your roof. If there is no drip edge, then the shingles should extend one inch to an inch and a half past the roof decking.
Installing Shingles Over a Drip Edge
What Is Overhang?
The overhang is the distance the first row of shingles extends past the drip edge. The purpose of combining the drip edge and the overhang is to keep water directed to the gutter and off of the fascia. Overhang also applies to the shingles on the side of the home.
Ideal Overhang Length
Once the drip edge is installed, the shingles should extend ½ inch to ¾ inch past the drip edge. If the shingles are allowed to extend too far, then they can be caught by the wind and damaged. If they do not extend far enough, driving rain can get under them and damage the roof deck.
Alsco® Serves Builders, Remodelers and Contractors
The world of metal accessories for roofing and siding products can seem confusing at times, even for the most experienced tradesman. Our team at Alsco Metals understands, and we will help you choose the right product the first time around.
We have over 70 years of experience in metal fabrication, and our designs are constantly improved upon by feedback from pro customers just like you. Did we mention that we’re one of the few providers with a dedicated on-site paint line to ensure that our colors match across all of our product lines?
Contact Alsco today for expert advice on your next roofing project.