Water control and drainage continuity · Lesson 2 of 4

Water control and drainage continuity: materials, standards and design constraints

The IBC and IRC sections for flashing, weeps and metal thickness; the standards for non-metal flashing; the specification sections to coordinate; and why gap sizes and weep spacing depend on the source.

You will be able to: Find the code sections that govern flashing and drainage, tell a code requirement from a publisher recommendation, and read gap sizes, weep spacing, laps and metal thickness against the document that sets them.

13 min · 12 slides · 10 questions

All lessons in this module

Slide 1 of 12

The code frame and whose edition

The code wording in this lesson is the 2021 IBC and IRC as the City of Seattle adopted them.

Your project follows the edition and amendments your own jurisdiction enforces.

Seattle marks section R703.4 as amended in Washington, so confirm the wording in your own edition.

Sources

2021 Seattle Building Code, Chapter 14 Exterior Walls (2021 IBC as amended by Seattle) - City of Seattle, Department of Construction and Inspections
2021 Seattle Building Code, Chapter 15 Roof Assemblies and Rooftop Structures (2021 IBC as amended by Seattle) - City of Seattle, Department of Construction and Inspections
2021 Seattle Residential Code, Chapter 7 Wall Covering (2021 IRC as amended by Seattle) - City of Seattle, Department of Construction and Inspections

Videos for this lesson

What this video shows: A Building Science Corporation clip on why a gap behind cladding matters and how reservoir claddings behave. Its gap sizes differ from BSD-105 and BSD-013, which is why the lesson shows gap sizes by purpose and source.

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

Glossary

Water-resistive barrier (WRB): The layer behind exterior cladding. IBC 1403.2 calls for not fewer than one layer of water-resistive barrier material.
Self-adhering flashing: A membrane flashing that sticks to the wall. IBC 1404.4 ties it to AAMA 711.
Liquid applied flashing: A flashing applied as a fluid that cures into a membrane. IBC 1404.4 ties fluid-applied membrane flashings to AAMA 714.
Pan flashing: Flashing at a window sill that is sealed or sloped to drain. IRC R703.4.1 calls for it where the window maker gives no flashing method.
Open head joint weep: A weep made by leaving a vertical mortar joint open just above the flashing. BIA recommends spacing it at no more than 24 in on center.
Air space: The space behind masonry veneer. BIA Technical Note 7 says a minimum 1 in air space is required, nominal in the IRC and specified in the IBC.