Kickout flashing—also called diverter flashing—is a critical roof component designed to direct rainwater away from exterior walls and safely into the gutter. When properly installed, it helps protect the building envelope from water intrusion and long-term damage.

Problems often arise when kickout flashing is missing, improperly installed, or altered. Without it, rainwater can concentrate at roof-to-wall intersections, allowing moisture to penetrate siding, trim, and wall assemblies. Over time, this can lead to rot, mold growth, and structural deterioration—often hidden behind the exterior with little to no visible warning signs.

Why Kickout Flashing Matters

Modern homes rely heavily on insulation and weather-resistant barriers, which reduce a building’s ability to “breathe.” While this improves energy efficiency, it also increases the risk of trapped moisture. Kickout flashing plays a key role in managing water by preventing runoff from being absorbed into the wall system.

Common Kickout Flashing Issues Found During Inspections

1. Kickout Flashing Was Never Installed

In older construction, kickout flashing was not always required or well understood. However, current building standards recognize its importance, especially where:

• A roof edge terminates at an exterior wall and gutter
• A wall continues past the lower roof slope
• Gutters end near chimneys or sidewalls

Without a kickout flashing in these locations, large volumes of water can miss the gutter entirely and flow directly into the wall.

2. Improper Installation

Even when kickout flashing is present, improper installation can make it ineffective. Common issues include:

• Leaking seams at the bottom of the flashing
• An incorrect diverter angle (it should be at least 110 degrees)
• Flashing that is not integrated correctly with the siding and step flashing

These defects allow water to bypass the flashing instead of being redirected.

3. Homeowner Modifications

Some homeowners alter or remove kickout flashing because they consider it unattractive. Common modifications include:

• Cutting the flashing height below the recommended 6 inches (some manufacturers allow 4 inches)
• Trimming it flush with the wall to make it less visible

Unfortunately, these changes significantly reduce effectiveness. Kickout flashing should be the same height as the adjoining step flashing to properly manage water flow.

The Bottom Line

Kickout flashing is a small, often overlooked detail—but it plays a major role in protecting a home from water damage. It should always be present where roof lines meet exterior walls and must be installed correctly to function as intended.

Because damage caused by missing or defective kickout flashing is frequently concealed, it’s an issue best identified during a professional home inspection.