Frass — sawdust-like debris — accumulating below a wooden beam indicates:

Frass is the material an insect pushes out of the wood it is tunnelling through, which makes its presence a live indicator rather than a historical one — debris accumulates where it is being actively produced and gets dispersed or cleaned away over time otherwise. Its texture also identifies the culprit. Carpenter ants eject coarse, fibrous shavings often mixed with insect parts; powderpost beetles push out a fine, flour-like powder from small round exit holes; drywood termites produce distinctive hard pellets. What matters for the report is that any of these means wood-destroying organisms in structural material above the pile, so the inspector documents the location and character of the debris and refers it to a licensed pest professional, who can identify the species and assess extent in ways a visual inspection cannot.

Frass is debris expelled from wood as an insect tunnels, so an accumulation below a beam indicates activity in the wood above it. The finding is documented and referred to a pest professional for identification and extent.

Wood-destroying insects produce characteristic debris: coarse fibrous frass from carpenter ants, fine powder from powderpost beetles, hard pellets from drywood termites. Subterranean termites instead pack galleries with soil and build shelter tubes.

A Pile Means Someone Is Digging, right now, directly above. Dust settles everywhere; frass lands in one spot and comes back.

Report the referral to a licensed pest professional. Species identification and treatment are typically outside the home inspection scope and often separately licensed.

• •Dismissing frass as construction dust or debris
• •Reporting the debris without noting its texture or location
• •Attempting species identification rather than referring it