Should I cover my deck with a tarp during winter in Edmundston NB?

No — covering your deck with a tarp during winter is one of the most counterproductive things you can do, and in Edmundston's climate it will likely cause more damage than leaving the deck fully exposed to the elements.

The instinct to protect your deck makes sense, but tarps create a sealed environment that traps moisture against the deck surface. In Edmundston, which sits in the upper Saint John River valley and regularly sees some of the heaviest snowfall totals in New Brunswick — often exceeding 300 centimetres of cumulative snowfall per season — a tarp laid over the deck catches and holds snow. As daytime temperatures rise, snow melts against the tarp, and the water has nowhere to go. It pools on the deck surface, soaks into wood grain or sits against composite boards, and then refreezes overnight. This trapped moisture cycle is far more damaging than natural snowfall that blows across and off an uncovered deck.

The lack of air circulation under a tarp is the other major problem. Moisture from melting snow, ground vapour rising through the deck boards, and condensation that forms on the underside of the tarp all get trapped in a humid pocket. In spring, when you pull that tarp off, you will very likely find mould and mildew growth on the deck surface, particularly in corners and along the house wall where airflow was most restricted. On pressure-treated lumber, this means a serious power washing and possibly sanding to remove black mould staining. On composite decking, mould can establish itself in the textured grain pattern and be difficult to fully remove.

The right approach is to let your deck breathe through winter. A well-built deck is designed to handle New Brunswick weather — the boards are spaced to allow drainage, the structure is fastened with corrosion-resistant hardware, and the framing is ventilated underneath. Snow sitting on the deck surface is not inherently harmful as long as the deck was built to handle the load. In Edmundston, where snow loads can be substantial, the important thing is to shovel when accumulation exceeds 30 centimetres to prevent excessive weight on the joists and beams. Use a plastic-edged shovel and push snow off the sides rather than scraping down to bare board.

If your concern is protecting outdoor furniture rather than the deck itself, the better solution is to move furniture into a garage or shed for winter. Metal furniture is especially vulnerable to Maritime humidity and should come inside — it rusts aggressively through a New Brunswick winter even without a tarp. Teak and cedar furniture can stay outside if properly oiled in the fall, but bringing it under a roof is always preferable. Planters should come inside as well, because the freeze-thaw cycling in Edmundston will crack ceramic and even some resin planters over the course of a single winter.

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