I spent six months chasing a musty smell in the southeast corner of my basement in Arvada. Every dehumidifier run, every caulk line I redid, nothing fixed it. Last week I pulled up the old carpet pad and found a small crack in the foundation where groundwater was seeping after heavy rain. I patched it with hydraulic cement from Home Depot, about $18 worth, and sealed the area with a waterproofing paint. The corner finally dried out in three days and the smell is gone. Turns out I should have checked the obvious spot way earlier instead of buying a $200 dehumidifier. Has anyone else traced a damp issue to a foundation crack they overlooked for months?
Why did it take pulling up carpet to check the slab? That corner probably smelled like wet dirt for months. I had a similar thing in my old place, turned out the downspout was dumping water right against the wall. Fixed it with a $6 extension, took an afternoon. Dehumidifiers are a band-aid, they never solve the actual leak. Good on you for finding it before the crack got worse.