That musty smell is your crawl space talking.

Musty Odors: diagnosed and explained.

A musty odor is one of the most common and most ignored crawl space symptoms we see. It smells damp and earthy, it gets stronger after rain or when the heat or air conditioning runs, and it never fully airs out no matter how many candles or open windows you throw at it. The reason is simple physics. A large share of the air in your living space rises up from the crawl space through gaps around plumbing, ducting, and flooring, so whatever the air under your house smells like, your house eventually smells like too. When that air is damp, it usually means moisture has collected under the home, and damp, dark, still conditions are exactly what mold and mildew need to grow on wood framing. The smell itself will not hurt your house, but what makes the smell will. The same moisture feeding the odor is softening posts, pads, and girders, and moisture-damaged supports are how musty smells eventually turn into sagging floors. The fix is never an air freshener. It is finding where the water comes from and stopping it. Deodorizing the living space treats the messenger, not the message. The smell fades when the moisture feeding it is shut off, which usually means a combination of drainage and sealing work matched to your water routes and airflow configured to your home rather than left to the weather. If the odor arrived alongside floor changes, have the supports checked too; our under house evaluation documents both in one visit.

For the repair side of this, the crawl space repair solutions page lists every method Dalinghaus installs, including the ones that fix problems other than musty odors.