Rainscreen
A rainscreen is an exterior wall approach that separates cladding from the water-resistive layer behind it with a drainage and often ventilated cavity. The outer cladding sheds most rain, while the cavity, flashing, and inner control layers drain, dry, and manage water that gets past the first line of defense.
What a rainscreen is
A rainscreen is a wall system that treats exterior cladding as a rain-screening layer rather than a perfect waterproof surface. Siding, panels, masonry veneer, or other cladding block and shed most rain. Behind them, an air space and water-resistive layer manage incidental water, allowing it to drain out and dry before it damages the backup wall.
Why walls need drainage
Wind-driven rain, cracks, joints, fasteners, window edges, construction tolerances, and aging sealants make it risky to depend on a face-sealed wall alone. Rainscreen design accepts that small amounts of water may enter. The wall is detailed so water hits a drainage plane, moves down by gravity, exits through flashings or weeps, and does not stay trapped against moisture-sensitive materials.
The cavity
The cavity is the space between cladding and the water-resistive layer or insulation behind it. It creates a capillary break, so water is less likely to be pulled inward by surface tension. If the cavity is open enough, air movement can also help dry wet cladding and sheathing. The cavity must stay continuous enough to drain, even around windows, corners, fire blocking, and support clips.
Drainage, ventilation, and pressure
Some rainscreens are mainly drained and back-ventilated: they provide a path for water and air behind the cladding. Pressure-equalized rainscreens go further by dividing the cavity into compartments so wind pressure inside the cavity can approach outside pressure, reducing the force that drives water inward through joints. Both approaches depend on careful detailing, not just a product label.
Control layers behind the screen
The wall behind the rainscreen still needs working control layers. A water-resistive barrier resists liquid water. An air barrier limits uncontrolled air leakage. Insulation controls heat flow. Vapor control may be needed depending on climate and assembly. In some high-performance walls, exterior insulation also helps keep the backup wall warmer and drier.
Flashing and exits
Drainage only works if water has places to leave. Flashing at windows, doors, shelf angles, foundations, roof-wall junctions, and floor lines directs water outward. Weep openings, vents, insect screens, and clear gaps must be placed so they do not clog or get buried by sealant, mortar, insulation, landscaping, or later repairs.
Materials and fire safety
Rainscreen cladding can be metal, fiber cement, masonry, wood, ceramic, stone, composite panels, or other materials. Support systems may use wood furring, metal rails, clips, or proprietary brackets. The cavity can affect fire spread, so taller buildings and combustible materials require special attention to fire stops, cavity barriers, tested assemblies, code requirements, and maintenance access.
Retrofits and repairs
Rainscreen retrofits are common when older walls have trapped moisture, failed sealants, or cladding that needs replacement. A retrofit may add furring strips, a new drainage mat, improved flashing, exterior insulation, or a new water-resistive barrier. The work should start with diagnosing leaks and drying paths; adding a new outer layer without fixing water entry or hidden decay can preserve the problem.
Why it matters
Rainscreens matter because long-lived buildings need walls that forgive small leaks and dry after storms. They shift the design goal from pretending rain never enters to managing what happens when it does. That approach can reduce rot, corrosion, mold risk, finish damage, and repair costs while improving the durability of the wider building envelope.