Signs of mold in a house
The nose almost always gets there first. Most of what grows in a house grows behind something, and by the time there is anything to look at, there has been something to smell for weeks.
The smell comes first
An earthy, cellar-like smell that concentrates in one room, sharpens after a heavy rain, or meets you at the foot of the basement stairs is the single most dependable early sign. If it comes back after a thorough clean, nothing reached the source.
Trust the version of your nose that has been away. A smell you cannot detect day to day but that greets you after a weekend elsewhere is real, constant odors stop registering within minutes of exposure.
What to look at
Forget the mental image of black fuzz. What you actually see is patchy discoloration, green, gray, chalky white, dark brown, laid out along wherever the moisture went rather than spreading in an even circle. And a mark that bleeds back through new paint is telling you plainly that the material behind it never dried.
Where it hides in an older Maryland house
Behind the paneling of a basement finished forty years ago, where studs were nailed flat to the block with no gap and nothing to stop vapor. Under carpet laid straight onto a slab. In the cavity behind the laundry connection. In the ceiling under an upstairs bathroom. And in whichever joist bay the air-conditioning condensate line happens to run through: a reliable one in this climate, where those lines run wet for five months a year.
In a rowhouse or a converted two-family, add the basement that serves every unit and is therefore nobody in particular’s responsibility, the room where problems get old before anyone claims them.
Which rooms those are depends on when the block went up. The attached and semi-detached housing through Dundalk and Essex puts the cellar stair and the party wall at the top of the list, because both belong to a joint rather than to a room. In the older detached stock around Catonsville it is more often the back addition: the place where a newer roof was tied into an older one and the two have been moving apart ever since.
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.