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Table of Contents
Introduction
This Drip Edge Quantity Calculator is a tool designed to help you accurately estimate the amount of drip edge material you need for your roofing project. It takes into account roof perimeter length, the length of a piece of drip edge, roof pitch, drip edge section overlap, and waste percentage allowance.
What Is Drip Edge?
Drip edge is a metal flashing installed along the edges of a roof to direct water away from the fascia and prevent water from seeping under the roofing materials. Drip edge helps to protect the underlying roof structure and the building’s exterior from water damage.
The use of drip edge is required by the International Residential Code, which is the basis of local residential building codes throughout the United States. Drip edge is also simply a good idea, and beneficial for roof performance. It’s also a required component for most roof system warranties.
How This Calculator Works
Our calculator takes into account several important factors, including:
- Roof Dimensions: Enter the length (one eave side) and width (one rake edge side) of your roof. The calculator multiplies these values by 2 when it calculates drip edge totals.
- Selecting for Hip Roof: This removes the slope input options from the calculator, because hip roofs don’t have rake edges. All hip roof edges are horizontal, so a roof pitch multiplier is unnecessary.
- Roof Slope: Your roof slope affects the actual length of the rake edges. Choose to input your roof slope as either standard pitch “X-in-12” or in degrees. Two linked slope fields ensure that you can work in your preferred format.
- Material Overlap and Waste Factor: Drip edge pieces are installed with overlaps, where each drip edge section overlaps the piece next to it; and a waste factor is added to account for trimming pieces as needed, common damage during installation, and mistakes.
- Cost Estimation (Optional): For cost estimating, you can enter an optional cost per piece, and the calculator will estimate the total material cost.
Amazon sells roof drip edge if if you want to check typical prices.
The calculator supports both imperial and metric units – simply select your preferred unit system at the top and the rest of the calculator will adjust.
Roof Drip Edge Calculator
Roof Drip Edge
Quantity Calculator
Notes on Drip Edge
To estimate the total amount of drip edge needed for a roofing project, follow these steps:
1. Measure the Perimeter of the Roof
The total required drip edge is the sum of the lengths of the eaves and rakes on a gable roof, or all the eaves on a hip roof (plus the total of all the overlaps between pieces of drip edge). An eave is the horizontal edge of a roof that extends beyond the exterior wall, providing protection from rain and directing water away from the building. A rake is the sloped edge of a roof that runs from the eave to the ridge found on gable-end roofs. That edge is typically referred to as the "rake edge".
The actual length of the edges of the surface of a sloped roof is calculated using the formula:
P=2(L + [W*M]) for a gable roof or P=2(L + W) for a hip roof
where P is total edge length, L is the length of the footprint, or plan view, of the roof, W is the width of the footprint of the roof and M is the roof pitch multiplier for the roof pitch.
For example, if a gable roof has a length of 50, a width of 30 feet, and a roof pitch of 6-in-12, the total perimeter is: P = 2(50+[30*1.118]) = 2(50+33.54) = 2(83.54) = 167.8 linear feet. Not 160 feet. For a hip roof with the same footprint, it would be 160 feet.
2. Account for Overlaps
The International Residential Code says "A drip edge shall be provided at eaves and rake edges of shingle roofs. Adjacent segments of drip edge shall be overlapped not less than 2 inches (51 mm). Drip edges shall extend not less than 1/4 inch (6.4 mm) below the roof sheathing and extend up back onto the roof deck not less than 2 inches (51 mm)."
Each piece of drip edge has to overlap the next one by at least 2 inches. Best practices may call for more overlap depending on the situation. Some roofers consider a 3-inch or even 4-inch overlap to be desirable. The overlaps add up and mean you'll need more material.
The purpose of overlapping the pieces of drip edge is to ensure a continuous effective water barrier, preventing water from seeping between the joints and reaching the roof deck. This overlap helps direct water properly off the roof, reducing the risk of leaks, wood rot, and potentially other structural damage.
3. Account for Waste
Add a 10% waste factor to account for trimming pieces as needed and possible damage. 10% is simply a standard number often used to estimate roofing material totals. You may have more or less.
Don't Forget:
How Drip Edge Gets Installed:
- Drip edge is installed along the eaves and rakes of the roof.
- At the eaves, it should be placed under the underlayment.
- At the rakes, it is installed over the underlayment to prevent wind-driven rain from getting under the edge of the underlayment.
About the Author
Jack Gray spent 20 years as a principal roof consultant with the Moriarty Corporation, an award-winning building enclosure consultant firm founded in 1967. Mr. Gray has worked in the roofing industry for over 25 years, with training and practical experience in roof installation, roof inspection, roof safety, roof condition assessment, construction estimating, roof design & specification, quality assurance, roof maintenance & repair, and roof asset management. He was awarded the Registered Roof Observer (RRO) professional credential in 2009. He also served as an infantry paratrooper in the 82nd Airborne Division and has a B.A. from Cornell University.