How do I protect my deck from carpenter ants in New Brunswick?

Carpenter ants are a serious threat to NB decks because our Maritime humidity creates ideal conditions for these wood-destroying insects. Unlike termites (which aren't a major issue in our climate), carpenter ants excavate galleries in moist, softened wood and can cause significant structural damage if left unchecked.

Carpenter ants are particularly problematic in New Brunswick because they thrive in the 60-80% humidity levels common during our spring and summer months. They're attracted to wood with moisture content above 15% — which describes most untreated lumber in our climate. The ants don't actually eat the wood like termites, but they hollow it out to create nesting galleries, weakening structural integrity over time.

Prevention is your best defense. Keep your deck dry by ensuring proper drainage around footings and posts. Clean out debris from between deck boards regularly, as trapped leaves and organic matter create moisture pockets that attract ants. Trim back vegetation that touches your deck — carpenter ants often use plants as highways to access wooden structures. Most importantly, address any moisture issues immediately. Check for leaking gutters, poor drainage, or areas where water pools against wooden components.

Moisture control is critical in NB's humid climate. Ensure your deck has proper ventilation underneath — don't block airflow with lattice or solid skirting unless it includes ventilation gaps. If you have a covered deck, make sure the roof doesn't trap moisture against wooden surfaces. Consider installing a vapor barrier between the ground and deck structure in areas with poor drainage. For existing moisture problems, a dehumidifier in enclosed under-deck areas can help during humid summer months.

For active infestations, look for telltale signs: small piles of wood shavings (frass) near wooden components, hollow-sounding wood when tapped, or actual ant trails. Carpenter ants are large (6-13mm) and typically black, most active at night. If you spot these signs, treat immediately with boric acid-based baits placed along ant trails — the workers carry the poison back to the colony. For severe infestations, professional pest control may be necessary.

Long-term protection strategies include annual deck maintenance with proper staining or sealing to reduce wood moisture content. In NB, this means staining every 2-3 years for pressure-treated lumber, annually for cedar. Consider upgrading high-risk areas (like posts near ground level) to composite or PVC materials, which carpenter ants won't attack. When replacing boards, choose pressure-treated lumber rated for ground contact (UC4A) for any components within 18 inches of soil.

When to call professionals: If you discover structural damage, see large colonies, or find ants inside your house (they may be nesting in the deck and foraging indoors), contact both a pest control specialist and a deck contractor. Structural repairs should be completed before treating the infestation to eliminate damaged wood that could harbor future colonies.

Need help finding a deck contractor to assess or repair carpenter ant damage? New Brunswick Decks can match you with local professionals who understand how to build and maintain decks in our challenging Maritime climate.