Wood that’s been damaged by termites tends to be hollowed out along the grain and may look completely undamaged. Inside, you can find ragged-looking “galleries” (tunnels in the wood) that are lined with dried mud, waste, and soil.
Other signs mud-lined “tubes” in visible areas around wood, and the sound made by knocking on termite-damaged wood: which produces a hollow sound. Damage in plaster and drywall may appear as tiny, dirt-lined holes.
Each year, roughly one in 30 homes are infested by termites and this can mean extensive damage to girders and joists.