Water management and enclosure basics · Lesson 1 of 4

Water management and enclosure basics: principles and terminology

Why rain is the first problem, the continuous enclosure, the four control layers, the 4 Ds, the working vocabulary of flashing, shingle-fashion laps and kickouts, where sheet metal sits, and the fall-protection boundary.

You will be able to: Define the key terms of water management, say what the four control layers and the 4 Ds are, name where sheet metal fits in keeping water out and letting it out, and state the safety boundary for roof work.

13 min · 12 slides · 11 questions

All lessons in this module

Slide 1 of 12

Rain is the first problem

EPA guidance says that in most climates rain is the largest source of water in buildings.

Building Science Corporation calls driving rain the largest single source of moisture for most walls and roofs.

Sheet metal flashing is made for the joints, edges and intersections where rain meets a building.

Sources

Moisture Control Guidance for Building Design, Construction and Maintenance (EPA 402-F-13-053, December 2013) - U.S. Environmental Protection Agency (archive snapshot host)
BSD-013: Rain Control in Buildings (John Straube, effective August 22, 2011) - Building Science Corporation

Videos for this lesson

What this video shows: Building Science Corporation on the four enclosure control layers in order of importance, water first, as its description states. The description calls it the water control layer.

Video: The Perfect Wall. Finally. by BuildingScience-com Corporation, on YouTube. Chosen from the video's published description.

Glossary

Flashing: A piece of metal or other material installed at a joint, an edge or an intersection so that it stops water entering there or sends water that has entered back out. The code language is that flashings prevent moisture entering the wall and roof through joints and at intersections.
Shingle-fashion: Laid like roof shingles: each upper piece laps over the piece below it, so water running down stays on the outside surface. The 2021 residential code requires approved corrosion-resistant wall flashing to be applied this way.
Reverse lap: A lap installed the wrong way round, with a lower piece lapped over an upper one, so water running down is led behind the upper piece. The DOE and PNNL guide calls avoiding it avoiding "reverse shingling".
Kickout: The first piece of step flashing at the bottom of a roof-to-wall joint, shaped to send roof water away from the wall and into the gutter. The DOE and PNNL guide says kick-out flashing directs rainwater into rain gutters.
Capillary break: A gap, drip or water-impermeable layer that stops water from wicking into a joint. EPA lists overhangs, copings and drip edges at a roof edge as capillary breaks.
Drainage plane: The layer behind the exterior cladding that carries water that gets past the cladding down and out, away from the building. The DOE and PNNL guide says to lap its materials over all exterior wall flashings.
The 4 Ds: The Whole Building Design Guide's four moisture strategies: deflection, drainage, drying and durability. Building Science Corporation groups rain control as three Ds without durability: deflection, drainage and drying.