Rainscreen
A ventilated cavity behind the cladding that lets walls drain and dry.
Quick Answer
A rainscreen is an exterior wall assembly with an outer cladding, a drained and ventilated air cavity, and a water-resistive barrier on the wall behind. The cladding blocks most rain, and the cavity lets water that gets past it drain away and the wall dry out. Pressure-equalized versions also reduce the force that drives water inward.
The Full Picture
A rainscreen separates the part of a wall that sheds most rain from the part that keeps water out. The outer cladding takes the weather. Behind it is a gap, from a fraction of an inch to several inches, and then a water-resistive barrier or air barrier on the structural wall. Water that passes the cladding drains down the gap and out at the base, and air moving through the cavity helps the wall dry.
Two principles are commonly distinguished. A drained and back-ventilated rainscreen relies on gravity drainage and airflow. A pressure-equalized rainscreen goes further by sizing openings and compartments so the cavity pressure nearly matches exterior wind pressure, reducing the driving force that pushes rain through joints.
Rainscreens can use many claddings: metal panels, fiber cement, terracotta, high-pressure laminate, wood, and stone. Support systems range from simple furring strips to engineered clip and rail systems. Because the cladding is attached through the cavity, thermal bridging through clips and the continuity of insulation and air barriers need design attention.
Detailing is what makes a rainscreen work. Flashing at the base, vents at the top, insect screens, and drained transitions at windows and penetrations all determine whether the cavity actually drains. Fire performance of the cavity and cladding is also reviewed, since combustible components and open cavities can be restricted by code on taller buildings.
Real Examples
Common Misconceptions
People assume: A rainscreen is a waterproof wall.
Actually: It is designed to manage water, not to be fully sealed. The cladding sheds most water, and the drainage cavity and weather barrier handle the rest.
People assume: Any wall with siding is a rainscreen.
Actually: Siding applied directly on sheathing has no intentional drainage and ventilation gap. A rainscreen has a defined cavity with openings to drain and ventilate.
Frequently Asked Questions
What is the purpose of a rainscreen?
To keep walls drier by letting the cladding shed most rain and giving remaining water a path to drain and evaporate, which protects the structure and insulation.
What is a pressure-equalized rainscreen?
A rainscreen designed so air pressure in the cavity closely matches outside wind pressure, which reduces the force driving rain through joints in the cladding.
How big should the rainscreen cavity be?
It varies by system and climate, from about 3/8 inch for simple drainage gaps to several inches for engineered systems. The manufacturer and the design team set the dimension.
What materials can be used for rainscreen cladding?
Metal panels, fiber cement, terracotta, wood, laminates, brick veneer with an air space, and natural stone are all used, depending on design and code limits.