In both residential and commercial construction, proper flashing around windows and doors is crucial for preventing water damage. While window flashing often receives significant attention, Flashing Exterior Doors is sometimes overlooked. This article highlights the importance of flashing exterior doors and outlines best practices for proper installation.
Why Flashing Exterior Doors is Essential
Exterior doors present a larger potential area for moisture intrusion than windows due to their size and frequent use. Ignoring proper flashing can lead to significant water damage, rot, mold growth, and costly repairs. Common misconceptions that lead to neglecting door flashing include:
- The belief that a porch roof or overhang provides sufficient protection: While overhangs offer some protection, they don’t fully shield doors from wind-driven rain or splashing water.
- Relying solely on a drip cap: Drip caps divert water away from the door head, but they don’t address potential leaks at the jambs or threshold.
- Focusing solely on window flashing programs: While important, window flashing programs shouldn’t overshadow the need for equally robust door flashing procedures.
Exterior doors, especially garage service doors and those in multi-unit buildings, often face significant exposure to the elements. These doors require comprehensive flashing systems to prevent water intrusion.
The image above illustrates a common oversight: a fully flashed window next to an unflashed exterior door. This demonstrates a double standard in flashing practices, even in protected areas. Note that the weather barrier does not constitute flashing.
Garage service doors, often located in unprotected areas, are particularly vulnerable to water damage if not properly flashed.
This image shows an improperly installed weather resistive barrier that doesn’t adequately cover the head flashing, leaving the door susceptible to water intrusion.
Even doors in covered areas, like this patio door, require proper flashing, especially when located near the edge of the covering and exposed to wind-driven rain.
Best Practices for Flashing Exterior Doors
A comprehensive flashing program for exterior doors should include:
- Threshold Flashing: Install self-adhered membrane flashing or a sill pan beneath the door threshold.
- Jamb Flashing: Apply self-adhered membrane flashing to both sides of the doorway, extending over the threshold flashing and at least 6 inches above the door opening.
- Door Installation and Sealing: Install the door with compatible caulking beneath the threshold and around the back of the brick molding or trim. Follow manufacturer recommendations for alignment and anchoring.
- Drip Cap Installation: Install an angled metal drip cap extending over the door head trim and returning at the ends.
- Head Flashing: Apply a self-adhered head flashing strip over the drip cap and extending at least 6 inches beyond the side jamb flashing.
- Weather Resistive Barrier (WRB): Install the WRB over the head flashing. The WRB can be installed over or under the jamb flashing depending on the installation sequence. If installed before the head flashing, cut the WRB at 45-degree angles in the upper corners to accommodate the flashing. Seal all WRB seams with manufacturer-approved tape.
Consult industry standards like FMA/AAMA/WDMA 300-12 for detailed guidance on exterior door flashing installation. These standards offer various options, including self-adhered flashing applied directly to the door frame before installation.
Conclusion
Flashing exterior doors is a crucial step in creating a weather-resistant building envelope. By implementing a comprehensive flashing program and adhering to best practices, builders can effectively prevent water damage and ensure the long-term durability of exterior doors. A third-party quality assurance program can help verify proper flashing installation.
