Drained and ventilated rainscreens

Cladding joints admit some rain. A wall needs a second line of control and a way to dry.

Separate the cladding from the backing wall with a drained cavity. Flashings return water to the exterior; suitable openings also allow cavity ventilation.

Context. The concept applies across climates; cavity design, vapour control, materials and fire requirements depend on the complete wall and its location.

1. Connect the drainage plane

   Resolve its continuity at the base, corners, penetrations and window flashings.

2. Support the cladding

   Coordinate battens or brackets with the structure and insulation. Preserve the intended drainage route.

3. Close the edges deliberately

   Detail outlets, ventilation openings and cavity barriers as parts of one assembly.

Window head

Water from above must discharge outward, not behind the window.

Cavity base

The outlet must remain open after the cladding and adjacent finishes are installed.

• Mortar, sealant or debris blocks drainage.
• A flashing stops short of the drainage plane.
• Attachments interrupt insulation or carry water inward.

Recladding a framed wall. Start at an existing window: draw the added wall depth, the sill extension and the water route before choosing the new siding.

What this guide covers. This is a drained, ventilated assembly. Pressure equalization needs additional compartmentation and air-barrier design; a cavity alone does not provide it.