In rainy BC and the Pacific Northwest, what is the best-value rainscreen detail (furring vs mats), and when is a 10 mm capillary break mandatory?
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For basic, straight walls, furring strips are a cheap and easy option. Use gap mats when you have complex shapes. If you’re building or renovating on the BC coast, stick to a 10 mm gap unless you know for sure you don’t need it.
In rainy BC and the Pacific Northwest, choosing the right rainscreen detail is crucial for managing moisture and ensuring the longevity of buildings. Here are some considerations:
Furring Strips vs. Mats
-Furring Strips: Traditional wood furring strips can be used, but they may cause thermal bridging and trapped moisture, leading to mold and rot. Using 1x4 or similar strips can work, but consider the potential drawbacks.
-Mats: Modern rainscreen systems like Climate-Shield use mats instead of furring strips, reducing thermal bridging to less than 3-5% and providing better moisture control. These systems are designed to allow bulk water and humid air to move through and evaporate freely.
In rainy BC/Pacific Northwest:
Best-value rainscreen: vertical furring strips over WRB—simple, effective, easy to flash, and durable.
When to use 10 mm drainage mats: on heavier cladding (stone, thick fiber cement) or where extra capillary break + airflow is needed; mats cost more but improve drying in very wet climates.
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Best-value rainscreen in rainy BC/PNW:
Furring (vented gap): cheapest, easiest, usually 19–25 mm.
Rainscreen mats: better drainage, costlier, harder to detail.
10 mm capillary break is needed when:
Cladding is low-permeance or non-ventilated.
Sheathing is sensitive to moisture (plywood/OSB).
Walls are exposed to driving rain.
Furring is usually fine for breathable claddings; mats or a 10 mm gap are required for higher-risk walls.
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Use furring for budget builds; 10 mm gap required for stucco/masonry or by local code.
In rainy BC/PNW, vertical furring strips give the best-value rainscreen:durable, simple, and compatible with most claddings. A 10 mm capillary break is needed behind smooth or impermeable claddings to prevent water bridging and ensure proper drainage.
Furring strips give best value; 10 mm capillary break is mandatory on most moisture-exposed walls under BCBC Part 9, except low-risk, well-sheltered cladding.
In the rainy climate of British Columbia and the Pacific Northwest, a drained and ventilated rain screen system using furring strips is generally considered the best-value approach for managing moisture and promoting longevity of exterior walls.
A 10mm capillary break (gap) between the cladding and the building’s weather-resistive barrier (WRB) is mandatory for most building permits issued after December 15, 2006, in many B.C. municipalities west of Hope and on Vancouver Island