A4.407 Water Resistance and Moisture Management — 2025 California Green Building Standards Code

A4.407.1 Drainage around foundations. Install foundation and landscape drains which discharge to a dry well, sump, bioswale or other approved on-site location.

A4.407.2 Roof drainage. Install gutter and downspout systems to route water at least 5 feet away from the foundation or connect to landscape drains which discharge to a dry well, sump, bioswale, rainwater capture system or other approved on-site location.

A4.407.3 Flashing details. Provide flashing details on the building plans which comply with accepted industry standards or manufacturer’s instructions. Details are shown on house plans at all of the following locations:

1. Around windows and doors.

2. Roof valleys.

3. Deck connections to the structure.

4. Roof-to-wall intersections.

5. Chimneys to roof intersections.

6. Drip caps above windows and doors with architectural projections.

Note: Reference details may be found in the Residential Sheet Metal Guidelines published by the Sheet Metal and Air Conditioning Contractors’ National Association Inc.

A4.407.4 Material protection. Protect building materials delivered to the construction site from rain and other sources of moisture.

A4.407.5 Ice and water barriers. In Climate Zone 16, an ice and water barrier is installed at valley, eaves and wall to roof intersections. The ice and water barrier shall extend at least 24 inches inside the exterior wall line or as specified by the manufacturer’s installation instructions.

A4.407.6 Door protection. Exterior doors to the dwelling are covered to prevent water intrusion by one or more of the following:

1. An awning at least 4 feet in depth is installed.

2. The door is protected by a roof overhang at least 4 feet in depth.

3. The door is recessed at least 4 feet.

4. Other methods which provide equivalent protection.

A4.407.7 Roof overhangs. A permanent overhang or awning at least 2 feet in depth is provided at all exterior walls.