When detailing roof assemblies, the placement of drip edge relative to felt (underlayment) is a common question. For American homes, the standard practice is to install the drip edge first along the eaves and rake edges, then lay the underlayment over it. This sequence ensures proper water flow, protects the fascia, and reduces the chance of water wicking back behind the edge. Understanding the correct order helps prevent leaks and extends roof life.
Understanding The Roles
The drip edge is a thin metal flashing that guides water away from the fascia and into the gutter. It also protects the roof deck edges from moisture intrusion and damage. The underlayment, or roofing felt, provides a secondary moisture barrier between the roof deck and the shingles, helping to prevent leaks if shingles are damaged or blown loose.
Recommended Installation Sequence
Drip Edge First, Then Underlayment
- Secure the drip edge to the fascia board along the eaves and rake edges using corrosion-resistant fasteners.
- Ensure the vertical lip of the drip edge extends beyond the fascia to direct water away from the building.
- Install the underlayment over the drip edge, extending up the roof deck as required by local code and manufacturer guidelines.
- Proceed with flashing, starter strips, and shingles as part of the typical roofing sequence.
Why this order matters: placing the drip edge before the underlayment ensures water shed from the roof follows the metal edge down and into the gutter, while the underlayment provides a secondary barrier over the edge to prevent moisture intrusion behind the flashing.
Common Variations And Local Code Considerations
The exact method can vary by region and product specifications. Some areas may have specific requirements for drip edge materials (aluminum, steel, or copper) or the placement relative to insulation and ventilation. Always check local building codes and manufacturer instructions for underlayment overlap and drip edge installation. In most U.S. installations, the standard practice remains drip edge installed first, then underlayment.
Practical Tips For A Durable Roof Edge
- Use corrosion-resistant fasteners and lap the drip edge pieces to create a tight, continuous line.
- Ensure the drip edge is continuous at corners with proper mitering and sealing as needed.
- When applying underlayment over the drip edge, maintain proper overlap with the roofing material to prevent water from bypassing the edge.
- Inspect the eaves after installation for any gaps or lifted sections that could allow water intrusion.
Potential Mistakes To Avoid
- Installing the underlayment beneath the drip edge, which can trap moisture and fail to shed water effectively.
- Using inappropriate fasteners that can corrode or loosen over time.
- Failing to follow the manufacturer’s overlap requirements or local code specifics for eave and rake edges.
Frequently Asked Questions
Q: Can I install drip edge over the felt? A: It is generally not recommended for standard asphalt shingles because it can impede proper water shedding and edge protection. Following the standard practice—drip edge first, then underlayment—provides better long-term performance.
Q: Do different climates affect this order? A: Most climates in the United States follow the same sequence, but areas with heavy rainfall or salt exposure may have additional requirements for flashing, sealants, and joint overlaps. Always verify with local codes and product guidelines.
Q: Is there a difference between eaves and rake edge installation? A: The same principle applies to both edges: install the drip edge first, then the underlayment, ensuring consistent protection along the entire roof perimeter.