Masonry Technology, Inc.

Ventilated Air Space for
Stucco & Adhered Stone

Prevent Entrapped Moisture. Reduce Cracking

Beginning in 2018, the International Building Code (IBC) Section 2510.6 Exception 2 states that

"Where the water-resistive barrier is applied over wood-based sheathing in Climate Zone 1A, 2A or 3A, a ventilated air space shall be provided between the stucco and water-resistive barrier."

IECC Climate Zones
IECC Climate Zones 1A-3A

Included in climate zones 1A-3A: Florida, Georgia, South Carolina, North Carolina, Alabama, Mississippi, Louisiana, Arkansas, Oklahoma & Texas

The rule applies to adhered masonry veneer, such as manufactured stone, thin cut natural stone, and thin brick.

Creating a continuous, predictable air gap between the scratch coat and the WRB with a rainscreen drainage mat improves the ability of the wall to drain and dry. The ventilated air space drains incidental moisture and enhances the performance of the WRB by eliminating hydrostatic pressure which mitigates leaks from fastener penetrations.

Ventilated Stucco Requirements

Air gap of at least 1/8" between water-resistive barrier and lath/scratch coat
Vented weep screed at the foundation for drainage
Vented opening at the top of the wall

When detailing it's important to think like water. Any water that enters the rainscreen drainage gap should be able to drain with gravity directly to the exterior. Any water vapor that remains in the air gap should be able to vent upwards through statck effect to the exterior.