Signs of mold in a house
Most mould is found by smell before it is found by sight, because the majority of it grows where nobody is looking.
The smell comes first
A musty, earthy smell that is stronger in one room, stronger after rain, or stronger at the bottom of the basement stairs is the most reliable early sign. If it returns after cleaning, the source was never reached.
A smell that disappears while you are away for a few days and hits you when you walk back in is worth paying attention to. You stop noticing a constant smell within minutes of being in it.
What to look at
Growth is not always fuzzy or black. It shows up as discolouration in patches, often greenish, grey, white or dark brown, and it follows moisture rather than spreading evenly. A stain that comes back through fresh paint is the clearest signal that something behind the surface is still wet.
Where it hides in an older Maryland house
Behind panelling in a basement finished in the 1970s or 1980s, where framing was set directly against a foundation wall with no gap and no vapour barrier. Under carpet laid over concrete. Inside the wall behind a laundry connection. Above a ceiling below a second-floor bathroom. In the joist bay a central air condensate line runs through.
In two- and three-family houses, add one more: the shared basement nobody inspects because it belongs to everybody and to nobody.
Worth an inspection if
- A musty smell returns after cleaning
- A stain reappears through fresh paint
- Flooring is cupping, lifting or feels soft in one area
- There was a leak in the past that was dried with fans and left at that
- The basement took water during a storm and was never properly dried out
Next step: Mold inspection across Maryland
If there is water in the home right now, that changes the priority — start here instead.