How long does cedar decking last in New Brunswick's Maritime humidity?

Western red cedar decking lasts 20 to 25 years in New Brunswick's Maritime climate when properly maintained, while eastern white cedar typically delivers 10 to 15 years before requiring significant board replacement. These timelines reflect the real-world performance that deck builders and homeowners across the province experience, not the optimistic figures sometimes quoted by lumber suppliers.

The distinction between western red cedar and eastern white cedar is crucial for New Brunswick homeowners because both are sold simply as "cedar" at many local retailers. Western red cedar, harvested primarily in British Columbia, contains significantly higher concentrations of thujaplicins, the natural compounds that resist fungal decay. In a province where relative humidity routinely sits between 75 and 85 percent through the summer months and coastal communities like Saint John, Moncton, and Shediac experience regular fog, that extra fungal resistance translates directly into years of additional service life. Eastern white cedar, while more locally available and typically $10 to $15 per square foot cheaper, simply cannot match that performance under sustained Maritime moisture exposure.

New Brunswick's freeze-thaw cycle is the other major factor that determines cedar lifespan. Between November and April, Moncton and Fredericton experience approximately 100 to 120 freeze-thaw cycles per winter. Each cycle drives moisture into the wood grain during the thaw and then expands it during the freeze, physically splitting wood fibres over time. This mechanical weathering process is relentless and affects cedar more than denser species because cedar is relatively soft at roughly 350 on the Janka hardness scale. The result is surface checking, which are small cracks along the grain that accumulate season after season. Surface checking alone does not indicate structural failure, but each check creates a new pathway for moisture penetration, accelerating the decay cycle deeper into the board.

Maintenance is what separates a 15-year cedar deck from a 25-year one in New Brunswick. The baseline requirement is annual cleaning with a dedicated deck wash product, followed by application of a penetrating oil-based stain or sealant. Film-forming stains that sit on the surface tend to peel in Maritime humidity because moisture vapor passing through the wood from below pushes the film off. Penetrating products soak into the grain and protect from within, flexing with the wood through seasonal movement rather than cracking and peeling. Plan to spend a full weekend each spring on this maintenance. Power washing is effective for cleaning but must be done carefully, keeping the pressure below 1,500 PSI and holding the nozzle at least 12 inches from the surface. Higher pressures tear cedar fibres and create a fuzzy, damaged surface that actually absorbs more moisture and deteriorates faster.

The underside of your cedar decking matters as much as the top surface, and this is where many New Brunswick decks fail prematurely. Moisture rises from the ground beneath the deck, condenses on the underside of boards, and creates a persistently damp environment that fosters mould and fungal growth where you cannot easily see it. Adequate ventilation beneath the deck structure is essential. Maintain a minimum of 18 inches of clearance between the ground and the bottom of your joists, and ensure the grade beneath the deck slopes away from the house to prevent water pooling. In particularly damp locations or low-lying lots common in river valley communities like Fredericton and Miramichi, laying a ground-level vapour barrier of 6-mil polyethylene beneath the deck can reduce the moisture rising from below by 60 to 70 percent.

Western red cedar decking in New Brunswick typically costs $35 to $55 per square foot installed, depending on the grade selected and the complexity of the build. Over a 20 to 25 year lifespan, factoring in annual maintenance costs of $200 to $400 per year for cleaning products and stain, the total lifetime cost per year of use comes in comparable to composite decking, which costs more upfront but requires less annual upkeep.

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