Underlay and cavities
| Site: | Wintec Learning |
| Course: | NZ Cert. Carpentry Level 4 - Learning |
| Book: | Underlay and cavities |
| Printed by: | Guest user |
| Date: | Wednesday, 10 June 2026, 12:55 PM |
Water penetration; weather tightness
Install cladding systems in accordance with manufacturer's requirements, along with documentation from the designer and building consent.
Fixing cladding over a drained and vented cavity is more weathertight than direct fixed cladding systems. Regardless, it must be installed and finished correctly.
- Read more on drained and vented cavity construction: BRANZ Wall Cladding Installation
- Read more on exterior cladding penetrations: BRANZ Cladding Penetrations
E2 External moisture is the section of the Building Code that relates to external roof, wall claddings and external openings constructed to prevent external moisture from causing undue dampness or damage.
- Building Performance - Building Code E2 External moisture
Weathertightness design basics
Learn about the four key principles of weathertight design:
- Deflection - how is water deflected from walls and critical junctions?
- Drainage - if water gets in can it drain?
- Drying - if water can't drain, can it dry?
- Durability - will materials be durable if occasionally wetted?
- Read about the 4 Ds of weathertight design: BRANZ The 4 Ds - deflection, drainage, drying and durability
Learn more about how exterior elements of the building help make up the lines of defence against water.
- Read: BRANZ Lines of defence
Learn how air movement and pressure moderation impact cladding and weathertightness.
Wall wraps installation
Watch this video on installing cavity battens and building wrap.