Professional roof installations rely on a strict sequence of materials to prevent water intrusion and long-term damage. Understanding whether you install drip edge before tar paper can change how your roof system performs and ages.
This article breaks down the key steps, material purposes, and common code expectations so you can make confident choices for each roof section.
| Order Step | Material | Primary Purpose | Key Consideration |
|---|---|---|---|
| 1 | Drip edge | Directs water away from fascia and prevents capillary action | Install first at eaves and rakes |
| 2 | Tar paper or synthetic underlayment | Secondary moisture protection and temporary cover | Overlap drip edge edges; avoid trapping excessive heat |
| 3 | Shingles | Primary weather barrier and aesthetic finish | Stagger joints and maintain proper ventilation |
| 4 | Flashing and sealants | Waterproof critical junctions like valleys and penetrations | Follow manufacturer and local code detailing |
Why Drip Edge Comes First
Drip edge is designed to shed water away from roof edges and into gutters. Installing it before tar paper protects the sheathing by preventing water from working behind the underlayment.
When drip edge is installed after tar paper, exposed edges can allow wind-driven rain to travel beneath the paper and into the roof deck over time.
Material Compatibility
Metal drip edge works well with asphalt-saturated tar paper and modern synthetic membranes. Ensure drip edge extends over the edge of the roof line so water drips clear of stacked materials.
Installing Tar Paper Over Drip Edge
Tar paper should be installed over drip edge on eaves and rakes to create a continuous moisture barrier. Use cap nails or staples designed for underlayment to secure the paper without tearing it.
Maintain proper overlap as specified by the underlayment manufacturer, typically at least two inches horizontally and vertically to avoid voids in protection.
Edge Detail Best Practices
At rake edges, trim drip edge to align with the roof plane while still covering the edge of the tar paper. This preserves both deflection and adhesion, especially in high-wind areas.
Material Choices and Performance
Choosing between traditional tar paper and synthetic underlayment affects durability, UV resistance, and handling during installation. Each option interacts differently with drip edge profiles and fastening patterns.
| Underlayment Type | Water Protection | UV Resistance | Compatibility with Drip Edge |
|---|---|---|---|
| Asphalt-saturated tar paper | Good temporary protection | Moderate, requires cover | Standard aluminum drip edge |
| Synthetic underlayment | High, stronger at overlaps | High, UV-stabilized | Most drip edge profiles |
Practical Recommendations for Roof Installers
- Always start with drip edge at eaves and rakes before any underlayment or shingles.
- Overlap tar paper properly over drip edge and secure according to manufacturer guidance.
- Choose drip edge material compatible with your underlayment and local climate conditions.
- Inspect edge detailing after installation to confirm water is directed away from the fascia.
- Follow local building codes, which often explicitly require drip edge in many jurisdictions.
FAQ
Reader questions
Should drip edge be nailed before or after laying tar paper?
Install drip edge first, then lay tar paper over the edge so the underlayment laps over the flashing to direct water into the gutter.
Can you install gutters without drip edge if tar paper is applied first?
Skipping drip edge increases the risk of edge rot and insect entry, even when tar paper is installed, because moisture can creep under shingles and fascia.
Does ice and water shield replace drip edge at the eaves?
Ice and water shield serves as a moisture barrier but does not replace drip edge, which controls surface water and protects the fascia from runoff.
How do you handle rake edges when drip edge is installed after tar paper?
Remove or notch the overlapping tar paper so the drip edge can lie flat, then reseal with compatible adhesive to maintain water shedding and appearance.