When renovating or building a roof, the order of components matters for long-term water protection. A common question is whether the drip edge should be installed before tar paper (roofing underlayment) or after. This article explains the standard practice, the reasoning behind it, and how to adapt to material or code specifics in the United States. Understanding the sequence helps prevent leaks and ensures proper water shedding away from the fascia and into the gutter.
What Drip Edge Is And Why It Matters
A drip edge is a thin, finished metal strip installed along the eaves and sometimes the rakes of a roof. Its main role is to guide water off the roof and into the gutter while protecting the underlying fascia from moisture. Proper placement also helps prevent wind-driven water from getting behind the roof covering. Drip edge comes in various finishes and gauges, with galvanized and aluminum options being common in residential projects.
Standard Roofing Sequence: Drip Edge, Tar Paper, Then Shingles
The prevailing method in many U.S. installations is to place the drip edge first along the eaves and rakes, then lay the roofing underlayment (tar paper or synthetic underlayment) over the roof deck, and finally install the shingles. In this sequence, the top edge of the drip edge is covered by the underlayment or shingles, directing water away from the fascia and into the gutters. The drip edge’s vertical leg remains exposed at the eave edge to form a clean channel for water runoff.
Why Install Drip Edge Before Tar Paper?
- Water Management: A properly installed drip edge helps ensure water drips off the edge rather than seeping behind the fascia. Having the drip edge in place first provides a defined landing for water as the underlayment overlaps it.
- Fascia Protection: Early installation protects the vulnerable fascia from potential water splash and moisture intrusion as the roof is completed.
- Fastening Support: The drip edge gives a stable guide for the tar paper to lay flat along the eave, reducing wind uplift risks for the underlayment near the edge.
Alternative Approaches and Variations
Some builders install drip edge after the tar paper in certain situations, particularly when using self-adhering underlayment or specialized systems. In those cases, the drip edge is positioned to cover the edge of the underlayment, with the flange tucked under the shingle line at the eave. Always follow the installer’s manual and local codes, as the exact interface can influence warranty coverage and performance.
Practical Steps for Proper Installation
- Prepare the eaves: Clean the rafter tails and ensure the fascia is secure and straight.
- Lay out the drip edge: Start at a corner and run the edge along the eave, securing with corrosion-resistant nails at appropriate intervals.
- Install tar paper or underlayment: Overlap the underlayment and position so its lower edge overlaps the drip edge’s outer lip, guiding water into the gutter. Tape or seal as required for the chosen material.
- Continue with underlayment on the roof plane: Work from the bottom up, ensuring a consistent overlap and minimal wrinkles.
- Apply shingles or tiles: Begin along the eave, covering the drip edge edge, with the shingles extending over the underlayment as specified by manufacturer guidelines.
Common Mistakes and How to Avoid Them
- Missing Overlap: If the underlayment does not overlap the drip edge, water can creep behind the edge during heavy rain or wind-driven conditions.
- Improper Nailing: Nails must be installed at the correct spacing and into solid framing, not just sheathing, to prevent edge uplift.
- Inconsistent Coverage: Irregular overlaps or gaps can create weak points where water can penetrate beneath the underlayment.
- Ignoring Local Codes: Some jurisdictions have specific drip edge requirements or flashing rules that may differ from general practice.
Material Considerations and Compatibility
Choose drip edge materials that resist corrosion and match the roof color or aesthetic. Common options include galvanized steel and aluminum. When selecting underlayment, consider whether a self-adhering or synthetic option is used, as this can influence how the drip edge interacts with the edge detailing. Always verify compatibility between the drip edge and the selected underlayment in the product manuals and any applicable building codes.
Inspection and Maintenance Tips
After installation, inspect drip edges for securely fastened nails and straight alignment. Check for loose sections after weather events and ensure the gutter system remains clear of debris that could back up water. Periodic checks during seasonal transitions help prevent minor issues from becoming leaks.
Conclusion: Following Best Practices for Longevity
In most U.S. residential roofs, installing the drip edge before tar paper underlayment is the established practice to optimize water management and protect the fascia. While variations exist for specific products or local codes, the core principle remains: create a reliable water-shedding interface from roof surface to gutter while safeguarding structural components. Refer to manufacturer guidelines and local building codes to confirm the exact sequence for a given project.