What Causes Roof Deck Rot in Vancouver Homes?

In our coastal climate, rotted roof decking is a serious structural concern driven by several recurring factors. Vancouver’s temperate rainforest environment means roofs are exposed to over 1,200 mm of annual rainfall, creating persistent moisture that can saturate the plywood or OSB sheathing if any minor breaches occur.

According to our field observations, the primary causes of roof deck rot include:

• Persistent Moisture and Humidity: The constant wet conditions during fall and winter months allow moisture to infiltrate the roofing surface. Once absorbed, this trapped water creates ideal conditions for fungal growth and structural breakdown.
• Inadequate Ventilation: Without proper airflow, warm, humid air from living spaces becomes trapped against the underside of the roof deck. This condensation saturates the wood from below. We frequently find that undersized or blocked venting is a major contributor to decay.
• Aging Materials: Older cedar shake roofs are naturally porous and can curl or crack over time, creating direct pathways for water. Many older homes also lack the modern ice and water shield underlayments required by current building codes.
• Flashing and Ice Damming: Poorly installed flashing around chimneys and skylights allows water to seep under shingles. Additionally, winter freeze-thaw cycles create ice dams that back meltwater up under the shingles, directly contacting the deck structure.

Identifying these issues early through signs like ceiling water stains or sagging sections is vital. We’re Ready To Help you assess your roof’s integrity. Claim your complimentary roof inspection today to ensure your home remains protected.

• Rotted Roof Decking: Vancouver Repair Solutions