What Is a Rainscreen, and Why Does BC Need It?

If you own or manage a building in the Lower Mainland, you have probably heard the word rainscreen. It is one of the most important concepts in BC construction, and it is worth understanding in plain language.

The idea in one sentence

A rainscreen is a ventilated and drained gap between the cladding and the wall behind it, so that any water that gets past the surface can drain down and dry out instead of soaking into the structure.

Why BC needs it more than most places

The coast gets heavy, wind-driven rain. No cladding surface is perfectly watertight forever; joints, penetrations and fasteners all give water a path. Without a drainage gap, that water sits against the sheathing and, over time, causes rot and the kind of expensive envelope failures that led to the region's well-known building repair history. The gap is what lets the wall dry.

What a rainscreen assembly looks like

From the inside out, a typical assembly includes:

1. Structural sheathing
2. A weather-resistive barrier (the drainage plane)
3. Vertical strapping that creates the ventilated gap
4. Continuous exterior insulation, on many modern assemblies
5. The finished cladding

Getting the transitions right at windows, doors, parapets and penetrations is where experience shows. That is the detailing that actually keeps water out.

When a building needs a rainscreen rebuild

Older buildings, especially face-sealed stratas and apartments from earlier eras, often need a full rainscreen rebuild: tear off the old cladding, test and repair the sheathing, install a new barrier, insulation and drainage gap, and re-clad. We do this work alongside envelope consultants and engineers on our restoration and rainscreen rebuild service.

If your building is showing moisture problems or is due for a re-clad, request a free assessment or call 604-315-2251. For the bigger picture, start with our complete siding guide.