Where does cedar rot start on a Vancouver fence?

Cedar rot on Vancouver fences almost always starts at the post base — specifically where the wood meets the soil or concrete at grade level. This is the single most vulnerable point on any cedar fence in Metro Vancouver's wet climate, and it's where most fence failures originate.

The reason is straightforward: the post base sits in a zone of constant moisture. Rainwater runs down the post, pools at grade, and saturates the surrounding soil for months at a time during Vancouver's wet season. Even naturally rot-resistant Western Red Cedar has its limits when it's sitting in wet soil or trapped against concrete that holds moisture against the wood. The heartwood of cedar resists rot well, but the sapwood (the lighter outer layer) is far more vulnerable — and most fence posts include some sapwood. Once rot takes hold at the base, it works upward through the post interior, often invisibly, until the post snaps or leans under wind load.

The second most common rot location is the bottom rail — the horizontal 2x4 or 2x3 that runs closest to the ground. Bottom rails collect debris, trap moisture against fence boards, and stay damp long after the rest of the fence has dried out. In shaded north-facing yards or under tree canopy (very common in Vancouver neighbourhoods like Kitsilano, East Van, and North Vancouver), bottom rails can stay wet for weeks at a stretch during winter. Moss and algae growth accelerates this — the biological matter holds moisture against the wood surface and creates ideal conditions for fungal decay.

End grain is the third critical vulnerability. Anywhere a cedar board or rail has been cut, the end grain is exposed — and end grain absorbs moisture roughly 10 to 15 times faster than face grain. The bottom of fence boards, the tops of posts (if uncapped), and any cut ends on rails are all high-risk zones. This is why post caps matter, why board bottoms should be kept 2 inches above grade, and why end-cut preservative should be applied to every cut surface during installation.

In Metro Vancouver's climate specifically, moss and mildew on the fence surface can also create localised rot conditions even mid-board. A north-facing fence board that stays green with algae for eight months of the year is trapping moisture against its surface continuously. Left untreated, this surface decay works inward over several seasons.

Practical steps to slow rot at every vulnerable point:

Set posts with a 4-6 inch gravel drainage bed below the base so water drains away rather than pooling. Use concrete that slopes away from the post at grade — not a flat collar that cups water. Keep board bottoms 2 inches above grade minimum. Install post caps on every post. Apply end-cut preservative to all cut surfaces during installation. Clean the fence annually with a pressure washer or diluted bleach solution to remove moss and algae. Re-seal or re-stain cedar every 2-3 years — this is non-negotiable in Vancouver's rainfall levels.

If you're inspecting an existing fence, probe the post bases with a screwdriver. If it sinks in easily, the post is rotted internally and needs replacement. Individual post replacement runs $150-$400 per post in the Metro Vancouver market, which is far cheaper than full fence replacement if you catch it early.

Need help finding a fence contractor for repairs or a replacement? Vancouver Fence Builders can match you with local professionals for free through the Vancouver Construction Network.