What is a Window Flashing?

Window FlashingA window flashing is a necessary part of proper window installation. To prevent leaks from rainwater or drafts, flashing is installed around windows. A window flashing itself is a thin, continuous piece of material which creates a seal. This seal, when properly created, prevents water from leaking around windows.

Is It Necessary?

Water leakage can lead to rot of the window frame structure or encourage the growth of hazardous molds as well as allow for burrowing insect infestation. The flashing is arranged to direct water down or away from the edges of the window itself. Commonly used flashing is available in sheet metal, waterproof tapes and vinyl pieces, according to Wise Geek.


Installation of flashing involves the removal of any nails around the window frame. The frame itself is pulled away from the house, including creating a gap between the frame and any siding, to create room for the flashing to be placed. Old caulking is cleaned away and the flashing is put in place beneath the siding. Proper installation involves using the original nail holes to prevent compromising the structure. Sealant is applied and the window is fitted against the flashing.

Varieties of Flashing

The key to proper window flashing is that the material be durable and waterproof. Vinyl flashing can be cut to fit difficult areas, but it is not recommended for cold climates as the vinyl may break. Metal is more durable, but the sharp edges and inflexibility of the metal make it difficult for non-professionals to handle. Tape flashing is the easiest of the three standard flashings to use, but it’s not suitable for hot climates due to the possibility of degradation.

Related Resource: Basement Window

Window flashing is recommended for any and all windows, regardless of an area’s precipitation, as it can help regulate energy consumption by preventing drafts. By preventing water damage to the window frame’s structure, window flashing aids in avoiding expensive home repair costs due to leakage. Exposed or concealed flashing is a matter of choice when building a home, but the inclusion of window flashing is an important protective measure for a home’s structure.