Wall Penetration Flashing

Flashing General Requirements

1. Use only corrosion-resistant flashing material such as aluminum, galvanized steel, and pealand-stick material. Corrosion resistance includes fasteners or other materials used to secure the flashing.

2. Use flashing, fasteners and other materials that are compatible with each other and with surrounding materials. Incompatible materials will react with each other and degrade over time. Example: do not use galvanized material with aluminum or with copper.

3. Flash and seal all wall penetrations and other vulnerable areas so that moisture will not enter the structure. Flash and seal any point where moisture could enter the structure regardless of whether it is mentioned in the list of areas where flashing is specifically required.

4. Install flashing “shingle fashion” so that upper flashing laps over lower flashing resulting in a drainage plane that will drain water toward a designed discharge point. This includes integrating flashing with the water-resistive barrier.

5. Extend flashing to the surface of the exterior wall finish material if necessary to assure that water is drained. This may be necessary with brick veneer, at horizontal joints in panel siding, with Z flashing at window and door headers, and at other drainage points.

Flashing Required Locations

1. Install flashing at all window and door openings. Refer to the window and door manufacturer’s installation instructions and to the instructions for any weather-resistive material (such as house wrap) or flashing material.

2. Install pan flashing at the window and door sills unless the window or door manufacturer’s instructions state otherwise. Integrate the pan flashing with jamb (side) fl ashing and with header (top) and with the weather-resistive barrier. Install all window and door flashing so that water drains away from the opening and out from the structure.

3. Install sidewall flashing where chimneys or other masonry construction intersect with walls.

4. Install projecting lips (sometimes called kick-out flashing) at chimneys and other sidewalls where a roof and vertical sidewall intersect. Kick-out flashing helps divert water away from this vulnerable intersection.

4. Install header/sidewall flashing under and at the ends of all copings and sills including masonry, metal, and wood.

5. Install header/sidewall flashing above all wood trim that projects from the adjoining wall and forms a shelf where water can collect.

6. Install flashing at the att achment point of exterior porches, decks, balconies, stairs, or fl oor assemblies to wood-framed construction.

7. Install sidewall flashing at all roof and wall intersections.

8. Install flashing at all built-in gutters.




Flashing Discussion

It is not possible to overstate the importance of flashing to the long-term integrity and health of the structure. Sealants such as caulk degrade over time and require maintenance. Exterior wall coverings move and crack creating gaps into which moisture can flow. Relying on building occupants to perform regular inspection and maintenance is not realistic. The best long term solution to avoiding moisture intrusion is a combination of a water-resistive building wrap and flashing integrated to form a drainage plane that prevents moisture from reaching vulnerable wood framing materials and drains the moisture away from the structure.

Flashing Best Practice

The IRC is mostly silent about how to install flashing. This leaves local building officials considerable latitude about what flashing techniques may be acceptable. The illustrations in this book present some recommended best practices. One of the best resources about flashing and water management in residential constructions is the Water Management Guide that should be available at www.eeba.org.