What maintenance does a composite deck need in New Brunswick?

Composite decking in New Brunswick requires cleaning at least twice per year, occasional mould treatment in humid conditions, and periodic hardware inspection, but it does not need sanding, staining, or sealing. This reduced maintenance profile is one of the primary reasons homeowners across the province choose composite over pressure-treated lumber, but "low maintenance" does not mean "no maintenance," and New Brunswick's maritime climate presents specific challenges that composite deck owners need to address proactively.

The twice-yearly cleaning schedule should align with the seasons that bookend winter. The first cleaning in late May, after the spring thaw and pollen season have passed, removes the accumulated winter grime, road salt residue, and organic matter that builds up under snow cover. The second cleaning in early October, before the leaves have fully dropped, clears the deck surface of the summer's buildup and prevents organic debris from sitting under snow all winter. For both cleanings, use a composite deck cleaner mixed according to the manufacturer's instructions, apply it with a soft-bristle brush or a push broom, and rinse with a garden hose. Power washing composite decking is generally acceptable but keep the pressure below 1500 PSI and use a fan-tip nozzle at least 20 centimetres from the surface. Never use a zero-degree nozzle on composite material as it can permanently scar the surface.

Mould is the most persistent maintenance challenge for composite decks in New Brunswick. Despite manufacturer claims of mould resistance, the reality is that the province's humidity, frequent rain, and cool temperatures create conditions where mould will grow on the surface of composite boards, particularly on north-facing decks and in shaded areas. The mould grows on the surface film of dirt and organic matter rather than penetrating the material itself, which is a meaningful difference from wood mould, but it is still unsightly and can make the surface slippery. When mould appears, clean it with an oxygen bleach solution, the same sodium percarbonate product used on wood decks. Apply, let it dwell for 10 minutes, scrub with a soft brush, and rinse thoroughly. Avoid chlorine bleach as it can discolour some composite products.

What composite decking does not need is equally important to understand. You should never sand composite boards. Sanding removes the protective outer cap or shell that most modern composite products feature, exposing the wood-fibre core to moisture absorption and dramatically accelerating deterioration. You should never stain or paint composite decking. The material is manufactured with integral colour and is not designed to accept topical finishes. Attempting to stain it will result in an uneven, peeling mess within a season. You should never seal composite decking either, as it does not absorb moisture the way wood does and a sealant film on the surface will trap dirt and create a hazy appearance.

However, composite boards are only the surface layer. The substructure of a composite deck in New Brunswick is almost always pressure-treated lumber, and that framing requires the same inspection and maintenance as any wood deck frame. Check the joists annually for signs of rot, particularly at connections and where they meet the ledger board. Inspect all metal hardware for corrosion. Check that the ledger board attachment to the house is sound and that the flashing is intact. The hidden fastener clips used on many grooved composite boards should be checked for any that have worked loose, which is less common than screw popping in traditional decking but still occurs after years of thermal cycling.

Keep the gaps between composite boards clear of debris. These gaps are engineered for drainage, and when they fill with leaf matter and dirt, water pools on the surface and flows toward the house instead of draining through. A putty knife or specialized gap-cleaning tool run between the boards during each cleaning session keeps drainage functioning properly.

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