A musty or earthy smell is the most common clue. Air from the crawlspace rises into the house through gaps in the floor, around pipes, and through ductwork, and it carries that smell with it. If the odor is stronger on humid days or when the AC first kicks on, the crawlspace is a likely source.
Allergy symptoms that ease when you leave the house are another sign. So is condensation on windows or floor registers in summer, which means there's more moisture in the house than there should be.
Soft or bouncy floors, especially near bathrooms and exterior walls, can mean moisture has been working on the joists and subfloor long enough to weaken them. Mold and rot often travel together.
Finally, look at the crawlspace vents and access door from outside. Torn plastic, standing water, or white fuzzy growth visible from the opening all mean it's time for a closer look.
If you notice any of these, a crawlspace inspection is the next step. We crawl the space, take moisture readings and photos, and show you exactly what's there before recommending anything.