Rainscreen siding, explained without the jargon

A wall stays dry because it can dry

Every cladding leaks eventually. Wind drives rain past laps, sealant ages, and window corners move. A rainscreen accepts that and gives the water somewhere to go: a ventilated cavity, usually a quarter inch to three quarters of an inch deep, between the siding and the drainage plane behind it.

That gap does two things. Liquid water drains straight down and out at the bottom, and moving air carries vapour away from the back of the boards. Cedar and fibre cement both last dramatically longer when their back face can dry, which is why we back-prime every piece and never fasten cladding tight to sheathing.

Where it matters most

South and west elevations, anything under a shallow overhang, and any wall that has been repainted more than twice in a decade. Repeated paint failure is almost never a paint problem. It is trapped moisture pushing the coating off from behind.