rainscreen

A rainscreen is a cladding system designed to separate exterior moisture from the structural wall by creating an air gap between the outer weather-exposed layer and the continuous weather-resistive barrier behind it. The system uses an exterior cladding installed in front of a drainage and ventilation cavity, which helps manage bulk water and moisture.

A typical rainscreen consists of three main parts: an outer cladding, an intentional air/water drainage cavity, and a backing weather barrier or waterproof membrane anchored to a structural wall. The cavity is ventilated and allows water that penetrates the cladding to drain down the wall and exit through weep holes or vents. Flashing and proper sealing at penetrations are essential.

Materials vary; cladding options include metal panels, fiber cement, brick or terracotta veneers, wood siding, and composite materials. The design must ensure adequate drainage, ventilation, and air-pressure equalization to prevent moisture accumulation.

Benefits include reducing moisture intrusion, aiding bulk water control, and potentially improving energy efficiency by allowing the wall to dry after rain. Limitations involve the need for careful detailing, ongoing maintenance, and potentially higher upfront costs; performance depends on proper installation of flashing, joints, and weep vents, with additional considerations for condensation in freeze-thaw climates.

Rainscreens are widely used in commercial and residential buildings, particularly in climates with frequent rain or moisture exposure. The concept has developed alongside advances in building envelopes since the mid- to late 20th century and remains a common approach to manage exterior moisture while enabling wall-system drying.