Wall Penetration Flashing

Description Window and door flashing in older homes is usually made from galvanized steel or aluminum. These materials are still used for components such as L flashing above window and door header trim, and Z flashing at the horizontal seam between panel siding. Wall penetration flashing around windows and doors in newer homes is often made from flexible plastic such as polyethylene, or from composite materials.

Wall penetration flashing for appliance vents and exhaust ducts is made from materials appropriate for the application. Galvanized steel is the common material for gas vent flashing. Galvanized steel, aluminum, and plastic are the common materials for exhaust duct flashing. Flashing for appliance vents at walls and roofs is sometimes called a thimble. Flashing for exhaust duct wall terminations is sometimes called a cap.

Most flashing around windows and doors is not visible during a home inspection because it is concealed behind wall coverings. This flashing should include pan flashing at the window and door sill, jamb flashing along the sides, and header flashing at the top. Inspecting concealed window and door flashing involves looking for water stains and water damage, which indicates that the flashing is not installed or not properly installed.

Visible Siding Flashing L flashing above window and door header trim and Z flashing at horizontal seams between sheets of panel siding should be visible at siding such as cement fiber, hardboard, and wood. J channel flashing should be installed around windows, doors and other wall penetrations when vinyl siding and aluminum siding is used.

Two diagrams side by side. Caption on leftmost diagram reads "Panel siding horizontal joint treatments." Caption on rightmost diagram reads "Flashing above doors and windows."

Image caption reads "Weep holes above door header."

Visible Brick Veneer Flashing Flashing should be installed and visible at several locations when brick veneer wall covering is used. Flashing locations should include at door headers and thresholds, at window headers and sills, at each floor level, and at the foundation. The flashing should extend past the brick just below the weep holes, but this is seldom done. Weep holes should be at least 3/16 inch diameter and be located at least every 32 inches. In practice, brick veneer flashing in all recommended locations is uncommon, even in newer houses. Weep holes may be visible in some recommended locations, but there is usually no way to know if flashing is installed behind the brick.

Diagram depicts brick flashing at windows

Visible Wall Covering Transition Flashing Flashing should be installed where one wall covering material meets a different wall covering material. An example is where siding or stucco meets brick veneer. The flashing should be visible at the transition, and should extend an inch or more over the lower wall covering. In practice, this flashing is uncommon, especially on older houses.

Diagram depicts flashing at different wall covering materials.

Other Wall Penetrations Exhaust ducts that penetrate a wall usually terminate in a cap. The cap flange should be set in a bed of sealant and the space between the opening and the cap should also be sealed. The space around plumbing pipes, condenser coolant tubes, electrical wires, light fixtures, and similar penetrations should be sealed. The sealant, if any, is not usually visible under wall coverings such as vinyl that use J channel flashing around wall penetrations.