Can I replace individual deck boards on a 15-year-old deck in Saint John?

Yes, you can absolutely replace individual deck boards on a 15-year-old deck in Saint John, and in most cases this is the smartest and most cost-effective approach. At the 15-year mark, a pressure-treated deck in New Brunswick is roughly at its midlife point, since well-maintained PT lumber lasts 15 to 25 years in the province's maritime climate. If the substructure — joists, beams, posts, and ledger board — is still sound, swapping out damaged or deteriorated surface boards is a straightforward repair that can buy you another decade of solid use.

Start by inspecting the boards you plan to keep. Press a flathead screwdriver into the wood at several points, especially near fastener holes and where boards sit on joists. If the screwdriver sinks more than 6 millimetres with moderate pressure, that board has soft rot and should be added to the replacement list. Also look for boards with significant cupping, where the edges have curled upward creating a trough shape, or boards with splits longer than a third of their length. In Saint John, the salt air from the Bay of Fundy accelerates weathering compared to inland communities, so you may find more surface degradation than you would on a similar-age deck in, say, Fredericton.

While you have boards removed, this is your best opportunity to inspect the joists underneath. Check every joist-to-beam connection and look carefully where joists meet the ledger board against your house. Rot at these connection points is common in the Saint John climate and is the real structural concern on an older deck. If you find soft or spongy joists, you have options: a joist with minor surface rot can be reinforced by sistering a new joist alongside it, bolted through with carriage bolts. A joist with deep rot needs full replacement.

When selecting replacement boards, match the dimensions of your existing lumber. Most decks built 15 years ago in the Saint John area used 5/4 by 6 inch pressure-treated decking. Current PT lumber from local suppliers will be slightly different in moisture content than your seasoned existing boards, so the new boards may shrink slightly over the first season. Leave a small gap of about 3 millimetres between the new board and its neighbours to account for this, and fasten with coated deck screws that are at least 75 millimetres long to ensure solid bite into the joists.

One practical consideration is colour matching. New pressure-treated lumber has a greenish tint that will not match your weathered grey boards. You have two options: replace the boards and let them weather naturally over 6 to 12 months until the colour evens out, or take this opportunity to sand and stain the entire deck surface for a uniform appearance. If you go the staining route, the new boards need to dry for several weeks before accepting stain properly.

Cost-wise, replacing individual boards on a deck in New Brunswick typically falls in the $500 to $2,000 range for minor repairs, depending on how many boards you are swapping and whether you are doing the work yourself or hiring it out. This is a fraction of a full deck replacement, which makes selective board replacement the clear winner when the underlying structure is still in good condition. The general guideline for when replacement makes more sense than repair is when more than 50 percent of the deck boards need replacing and you are finding structural issues in multiple beams or joists simultaneously.

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