Which decking lasts longest through New Brunswick freeze-thaw?

Composite decking with capped polymer boards is your best bet for New Brunswick's brutal freeze-thaw cycles — properly installed, quality composite can last 25-30 years with minimal maintenance, outperforming most other options in our climate.

Here's the core problem with NB winters: we don't just get cold, we get repeated freeze-thaw events throughout the season. Temperatures swing from -25°C to above freezing multiple times each winter, and any material that absorbs water will eventually crack, heave, or rot. That's what eliminates a lot of otherwise decent decking options.

Capped composite (brands like Trex Transcend, TimberTech AZEK, or Fiberon Horizon) is the top performer because the solid polymer cap prevents moisture absorption almost entirely. Unlike older uncapped composite that could swell, stain, and grow mould, capped boards shed water and resist the expansion-contraction cycle well. Expect to pay $45–$75 per square foot installed in the NB market for a quality composite deck — mid-range for a 400 sq ft deck runs roughly $18,000–$25,000 depending on complexity, railing choice, and site access.

PVC decking (full cellular PVC like AZEK) goes one step further — no wood fibre at all, so there's truly nothing to absorb moisture. It's slightly more expensive but performs exceptionally well near coastal areas like Saint John or Shediac where salt air adds another layer of attack on materials. If your deck faces the Bay of Fundy or the Northumberland Strait, PVC is worth the premium.

Pressure-treated lumber is still widely used across NB and remains a legitimate choice — especially ACQ-treated 5/4 decking — but it requires annual cleaning and sealing to hold up well, and you will see some checking and warping over time from freeze-thaw. Budget $18–$30 per square foot installed. Many NB homeowners use PT lumber for the structure (joists, beams, posts) and composite for the decking surface — that's actually a smart hybrid approach that keeps costs reasonable.

Hardwoods like Ipe are extremely durable but expensive ($50–$80/sq ft installed), require annual oiling, and can get slippery when wet — a real concern on icy NB mornings.

Whatever material you choose, the framing and drainage details matter as much as the boards themselves. Joists should be spaced no more than 12" on-centre for composite (many manufacturers require this for warranty), with proper gapping between boards (typically 3–5mm) to allow drainage. Footings must go below frost depth — 4+ feet in most of NB, deeper inland toward Fredericton and Woodstock. A deck that heaves because footings are too shallow will fail regardless of how good the decking boards are.

A building permit is required for most decks in New Brunswick — if you're in Moncton, Fredericton, Saint John, or another municipality, contact your city's planning and development office. Rural homeowners should reach out to their Regional Service Commission. Don't skip this step; it protects you at resale and ensures the structure is built to code.

Browse licensed deck builders in our directory at New Brunswick Construction Network — getting two or three quotes is always worthwhile, and a good contractor will help you match the material to your specific site, sun exposure, and budget.