Windows, doors and opening transitions · Lesson 1 of 4

Windows, doors and opening transitions: principles and terminology

Why openings leak, how a drained opening works, the sill pan, the jamb strips, the pieces named at the head by TN05, Guertin and the AFS catalog, the lap order, and the fall-protection boundary at an open rough opening.

You will be able to: Name the parts of a flashed window or door opening, explain drained installation, shingle-fashion lapping, back dams and end dams, and state the safety boundary at an open wall opening.

10 min · 10 slides · 7 questions

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Slide 1 of 10

Why openings are flashed

Missing or inadequately installed flashing at a window or door can lead to water intrusion and moisture damage to building materials.

A window or door interrupts the wall's water-resistant layer. The sill pans and metal head flashings AFS fabricates give water at the opening a safe path out to the face of the wall.

Sources

TechNote: Window and Door Flashing - Code Requirements and Best Practices (September 2015; quotes the 2015 IRC section R703.4), as hosted by the Town of Ocean City, Maryland - TechNotes builder series
AFS product catalog: Head Flashing and Sill Pan Flashing (Windows and Doors category) - Architectural Flashing Supply

Glossary

Rough opening: The framed hole in the wall that a window or door unit is set into; the sill pan, jamb and head flashing are built around it.
Sill pan (pan flashing): Flashing installed at the base of the rough opening so water that gets in through or around the unit drains back out to the exterior.
Back dam: The raised edge at the interior side of a sill pan that stops water running toward the inside of the building.
End dam: The raised edge at each end of a pan flashing that stops water running sideways off the pan and into the wall.
Shingle fashion: Lapping layers so the top layer is over the bottom layer, the way shingles overlap, so water sheds down and out instead of behind a layer.
Reverse lap: A lap in which a lower layer sits over an upper one, so water running down the wall is directed behind the lower layer.
Water-resistive barrier (WRB): The material behind the cladding that provides the drainage surface protecting the wall from rain water; house wrap is a common example.
Drained installation: A way of installing a window or door that expects a little water to get in and collects it in a pan flashing that drains it back out to the exterior.