To figure out how much drip edge you need, you primarily calculate the total length required by measuring the edges of your roof. This calculation is based on the dimensions of the eaves and rakes of the roof, which are the bottom and side edges.
What is Drip Edge?
A drip edge is a crucial component of a roofing system. As per the reference, it is a metal strip that goes beneath the underlayment. Its primary purpose is to direct water away from the fascia and into the gutters, protecting the roof deck and fascia board from water damage.
Calculating How Much Drip Edge You Need
The main way to "figure out" drip edge, in terms of quantity, involves measuring the linear feet of the roof edges that will receive the drip edge.
Here’s a step-by-step approach based on the reference:
- Identify Eaves and Rakes:
- Eaves: These are the lower, horizontal edges of the roof that typically overhang the walls and are where gutters are usually installed. The reference identifies these as the bottom edges.
- Rakes: These are the sloped edges of the roof that run from the eave to the ridge. The reference identifies these as the side edges. The reference specifically states, "The side of the house will also need a rake edge."
- Measure the Lengths: Carefully measure the linear length of all the eaves and all the rakes on your roof structure using a tape measure. It's often easier to do this from the ground or a ladder if safe, or using architectural plans.
- Sum the Measurements: Add up the total length of all eave sections and all rake sections.
- Account for Overlap: Drip edge pieces are typically installed with an overlap of about 1 inch (or as recommended by the manufacturer) where they meet. You'll need to factor in this overlap when calculating the total number of pieces, but the total linear feet needed is simply the sum of your measurements plus a little extra for waste and overlaps across the total length.
- Add for Waste: It's wise to add an extra 5-10% to your total measurement to account for cuts, mistakes, and waste.
Example Calculation:
Let's say your roof has:
- Two eave sections, each 40 feet long.
- Four rake sections, each 25 feet long.
| Roof Section | Length per Section | Number of Sections | Total Length (ft) |
|---|---|---|---|
| Eaves | 40 ft | 2 | 80 ft |
| Rakes | 25 ft | 4 | 100 ft |
| Total | 180 ft |
So, you need approximately 180 linear feet of drip edge before accounting for waste and overlap specifics. Adding 10% for waste brings the total needed closer to 198 feet. You would then purchase drip edge in standard lengths (e.g., 10 feet) and calculate how many pieces are required.
Drip Edge Placement: Eaves vs. Rakes
The placement relative to other roofing materials differs slightly between eaves and rakes:
- Eaves: The drip edge is installed beneath the underlayment along the eaves. This allows water running down the roof deck and underlayment to flow over the drip edge and into the gutter.
- Rakes: The drip edge (often called rake edge specifically) is typically installed over the underlayment along the rake edges. This protects the underlayment on the sides from wind-driven rain.
By measuring the lengths of both eaves and rakes, you can accurately determine the amount of drip edge required for your roofing project, ensuring proper protection against water damage.
