A basement usually smells musty after water damage because moisture is still trapped somewhere in the space, even if the floor looks dry. After a leak, flood, sump pump issue, sewer backup, or foundation seepage, water can move into drywall, carpet, baseboards, insulation, storage boxes, and framing. When moisture remains, mold can start growing behind finished surfaces and create the stale, earthy odour many homeowners notice. If the smell does not go away, mold testing Toronto services and professional mold removal Toronto support may be needed to find the source.