Architectural Flashing Supply
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Water control and drainage continuity · Lesson 1 of 4

Water control and drainage continuity: principles and terminology

Why continuity matters more than any single material, the three rain-control strategies, where a wall is interrupted, the terms for the pieces that carry water out, who decides, and the fall-protection boundary for site visits.

You will be able to: Explain why the water control layer must be continuous, name the places it is interrupted, define the flashing and drainage terms a detail depends on, and say who decides what on a project.

10 min · 9 slides · 8 questions

All lessons in this module
Slide 1 of 9

The layer must be continuous

Building Science Corporation (BSC) calls the layer that stops liquid water the water control layer.

BSC says a control layer works only if it is continuous.

The water control layer of the wall must connect with the water control layer of the rough opening where the window sits.

BSC writes: "Where there is discontinuity, we often find leaks."

Sources

Videos for this lesson

What this video shows: A Building Science Corporation clip. Its description says the water control layer must be continuous, that the wall layer connects with the layer of the rough opening, and that where there is discontinuity leaks are often found.

Video: Cup of Joe - Continuity of Control Layers by BuildingScience-com Corporation, on YouTube. Chosen from the video's published description.

Glossary

Water control layer
The layer in a wall that stops liquid water. Building Science Corporation says it must be continuous, including across the rough opening of a window.
Drainage plane
A water repellent material behind the cladding, built to drain water that gets past the cladding down and out of the wall.
End dam
The turned-up end of a flashing that stops short. It keeps water that the flashing collected from running off the end into the wall. BIA Technical Note 7 says at least 1 in.
Back dam
The upturned rear edge of a window sill flashing or sill pan. Building Science Corporation, describing a fluid-applied window sill flashing, says there should always be one.
Weep
An opening immediately above a flashing that lets the water it collected out of the wall.
Counterflashing
A flashing that protects the top edge of the flashing below it by lapping over it. BIA says it generally overlaps roof flashing a minimum of 3 in.
Receiver
A sheet metal piece in the wall made to receive and anchor a counterflashing. For example, BIA Technical Note 7 describes a through-wall metal drip edge fabricated to receive and anchor it.