Rain Screen Wall Assembly: Why and How A rain screen wall assembly is an exterior wall detail that protects a building by shedding bulk water at the outer cladding, providing a ventilated cavity for drainage and drying, and keeping the weather-resistant barrier (WRB) and air barrier behind the cladding. For DIY eco homebuilders, a properly designed rain screen wall assembly reduces rot, improves cladding life, and pairs well with continuous exterior insulation to cut thermal bridging. This guide explains what a rain screen does, the main system types, material choices, a step-by-step build sequence for new and retrofit work, window and penetration detailing, and realistic cost drivers so you can plan a durable, moisture-managed exterior. TL;DR: - Rain screen walls keep bulk water off the WRB, provide a ventilated cavity (typically 10–25 mm) for drying, and reduce rot risk — use them in coastal, rainy, or freeze-thaw climates. - For most DIY projects choose a drained-and-ventilated syst...