Log what you're seeing
Track where it's showing up, when you first noticed it, whether it tracks with weather or seasons, how it's changed, and any prior attempts to deal with it. A few photos and rough measurements go a long way toward a more productive first call.
Read the local context
Champaign's problem runs on a seasonal cycle that reverses twice a year, and the city's housing gives it two places to happen. Through humid prairie summers, warm air meets cool basement walls and floors -- and with basements as common as they are in a city that grew from the 1855 railroad settlement onward, that is where growth most often develops, on framing, stored contents and finished basement rooms, without a leak anywhere. Through a long heating season the flow reverses and indoor moisture reaches cold attic sheathing, where a bath fan terminating in the attic will stain and eventually delaminate it, repeating every winter until the duct is corrected. Both halves are driven by air rather than water, which is why an inspection that hunts only for leaks can come back empty.
Ask about what won't be visible later
The mold on the surface is only part of the story. A solid written scope spells out the prep work and verification steps that disappear once the job looks finished, not just the finished appearance.
Line scopes up side by side
Check each proposal for how it handles protection of the space, access, materials, permits, testing, cleanup, restoration, what's excluded, warranty terms, and change-order rules.
What official local sources add
The climate does most of the work here, in both directions. Through humid East Central Illinois summers, warm moist air condenses on cool below-grade surfaces, and on this flat, slow-draining prairie ground the soil beside a foundation stays wet long after the rain has stopped — which is why basement and crawlspace humidity is the dominant local source. Through the winter the direction reverses and moisture condenses in cold attic cavities, where a fan discharging into the attic rather than outside will do damage every year. Neither is fixed by cleaning; both are fixed by changing where air and water go.
Sources were reviewed 2026-07-26. Confirm your parcel's flood-zone status, drainage conditions, and current stormwater permit requirements with the City of Champaign before authorizing any work that changes grading or drainage.