A rainscreen is the gap that saves the wall. Rather than relying on the cladding alone to keep water out, the system accepts that wind-driven coastal rain will get behind the surface, then gives that water a clear path to drain and dry. On the South Coast that is not a precaution, it is the baseline. Months of damp weather, salt-laden wind off the water, and driving rain against every west and south elevation all push moisture past the cladding face. A drained, vented cavity is the difference between a wall that sheds our weather and one that quietly rots from the inside out.
Why the code demands a cavity
The drained and vented rainscreen is written into the BC Building Code for hard-earned reasons. The leaky-condo crisis of the 1980s and 90s exposed how badly face-sealed walls fail in this climate. Buildings were wrapped tight and trusted to keep every drop out, but no seal stays perfect forever. Once water got in, it had nowhere to go and no way to dry, and framing turned to compost behind intact-looking stucco.
The fix is simple in principle: assume water will get behind the cladding, then manage it. A modern rainscreen wall does that with a few layers working together.
- A continuous water-resistive barrier and properly lapped flashings that direct any water that gets in back to the outside.
- Vertical furring or strapping that holds the cladding off the barrier and creates the drainage gap.
- A capillary break, so water cannot wick across the cavity and back into the structure.
- Venting at the top and bottom of the cavity, screened against insects, so air moves through and dries the framing between storms.
That last point is the part homeowners often miss. A gap that drains but does not breathe will hold humidity. The chimney effect of bottom-to-top venting pulls dry air up behind the cladding, and that airflow is what keeps the sheathing sound through a wet Lower Mainland winter.
Detailing that makes the cavity actually work
A rainscreen is only as good as its weakest transition. The cavity does nothing if water can dam behind a window head or pour into the wall at a deck ledger. The real craft is in the details, and that is where our trades-first approach earns its keep. We integrate the water-resistive barrier with head, jamb, and sill flashings at every window and door, flash penetrations for vents, hose bibs, and electrical, and keep the cavity open and screened so it can drain and vent as designed.
The strapping layout matters too. Furring has to land on studs to carry the cladding, leave clear vertical drainage paths, and keep the venting continuous from bottom to top rather than chopped into dead pockets behind trim. We build these assemblies behind whatever finish suits the home, including fiber cement, stucco, panel, board and batten, and natural cedar. The cavity works the same way behind all of them; the cladding is just the part you see.
Retrofitting a rainscreen during a re-clad
A re-clad is the best opportunity you will ever get to add a proper rainscreen to an older house. Once the old cladding is off, furring the wall out to create a drainage gap is the single highest-value upgrade available, and it costs far less to do then than after the next failure. We see plenty of face-sealed walls across Greater Vancouver and the Fraser Valley that never had a cavity, and pulling the cladding tells us quickly whether there is hidden moisture damage to address before the new wall goes on.
If you are repairing a section rather than re-cladding the whole house, that is worth a conversation too. Our cladding repair work tends to reveal whether a wall has a working cavity or not, and what it would take to bring it up to a drained, vented standard. Whether it is new construction or a tired older home, the rainscreen is the foundation everything else depends on, and getting it right is what keeps the wall dry for decades.