Carpenter Bee Damage on Decks: Prevention and Repair

How the damage grows

Each round, half-inch hole is the entrance to a tunnel the female bores along the grain to lay her eggs. One hole is minor, but carpenter bees reuse and extend galleries every year, so a deck that is ignored gets progressively more tunneled. Over time the galleries weaken railings, fascia and trim.

Woodpeckers make it worse — they chase the larvae inside and tear open the wood to reach them, turning neat holes into ragged damage.

Treat, then seal (order matters)

The correct sequence is to treat the galleries first so returning and emerging bees contact the treatment, then plug the holes once activity has stopped. Sealing an untreated hole is the classic mistake: it traps bees that simply tunnel out a new exit, often right beside the old one.

After treatment, fill holes with wood filler or a dowel and sealant so they are not reused the following spring.

Protect the wood so they move on

Carpenter bees strongly prefer bare, unpainted, weathered softwood — the kind of cedar and pine common on Joliet-area decks and fascia. Painting or sealing exposed wood makes it far less attractive and is the best long-term prevention. Hardwoods and finished surfaces see much less drilling.

• Paint or seal deck rails, fascia and exposed trim.
• Replace or finish badly weathered boards bees have targeted.
• Re-check and re-seal finishes every few seasons.

Do carpenter bees sting?

Mostly no. The males hover aggressively and are territorial but cannot sting; the females can sting but rarely do unless handled. The real concern is the structural damage to wood over the years, not aggression — which is why prevention focuses on the wood, not on avoiding the bees.