Uploaded August 2023 | Updated September 2026, 1 hour ago
There's two types of windows - windows that leak and windows that will leak. We have to protect our window openings and provide a means of drainage to ensure that an accumulation of water does not result in water damage or rot.
In this video, we explain two of the most critical window flashing details to get right - the window sill detail, and the window head detail.
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Music:
Chill Abstract Intention
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Rough sills should be sloped to the exterior of the assembly to drain out any water that happens to find a path behind the window assembly, with a back dam to prevent any wind driven water from entering the interior. The rough opening is flashed with a fluid applied flashing rather than flashing tape, since this can provide a more reliable form of monolithic water control, without having to do “origami” with the tape. The window unit
is then installed over shims to provide a level surface for the frame, and to provide a space for water to freely drain. While window heads may be detailed slightly differently depending on the type of weather resistive barrier specified, all window heads should have the same basic characteristics. The rough opening at the head should be flashed continuously with the flashings at the jamb and the sill. Flanged windows are set into the flashed rough opening with a continuous bead of sealant, and flashed either to the sheathing or to the weather resistive barrier, and protected with an additional drip cap flashing to kick water away from the window opening. The weather resistive barrier must be integrated into the window head flashings, whether it’s shingled over the drip cap, as in the case of building wraps, or reverse flashed with a high quality tape or a fluid applied flashing product, a common strategy in some self-adhered and integrated weather barrier applications.
There's two types of windows - windows that leak and windows that will leak. We have to protect our window openings and provide a means of drainage to ensure that an accumulation of water does not result in water damage or rot.
In this video, we explain two of the most critical window flashing details to get right - the window sill detail, and the window head detail.
Check out our resources page here and sign up for our newsletter for free weekly articles and content: asiri-designs.com/resources-1
eBooks and high performance CAD Details: asiri-designs.com/shop
Consulting and Other Services: asiri-designs.com/our-services
Follow my Instagram - @asiridesign
instagram.com/asiridesigns
Music:
Chill Abstract Intention
-------------------------------------------------------------------------------------------------------------------------
Rough sills should be sloped to the exterior of the assembly to drain out any water that happens to find a path behind the window assembly, with a back dam to prevent any wind driven water from entering the interior. The rough opening is flashed with a fluid applied flashing rather than flashing tape, since this can provide a more reliable form of monolithic water control, without having to do “origami” with the tape. The window unit
is then installed over shims to provide a level surface for the frame, and to provide a space for water to freely drain. While window heads may be detailed slightly differently depending on the type of weather resistive barrier specified, all window heads should have the same basic characteristics. The rough opening at the head should be flashed continuously with the flashings at the jamb and the sill. Flanged windows are set into the flashed rough opening with a continuous bead of sealant, and flashed either to the sheathing or to the weather resistive barrier, and protected with an additional drip cap flashing to kick water away from the window opening. The weather resistive barrier must be integrated into the window head flashings, whether it’s shingled over the drip cap, as in the case of building wraps, or reverse flashed with a high quality tape or a fluid applied flashing product, a common strategy in some self-adhered and integrated weather barrier applications.
