Signs of mold in a house
Smell beats sight almost every time here, for a simple reason: most of what grows in a house grows behind a surface, and nobody is looking at the back of a wall.
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 discoloration in patches, often greenish, gray, 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 the wall is plaster rather than drywall (the norm in the pre-war housing around Montclair and Plainfield), the stain travels further before it surfaces, because plaster holds and spreads what drywall would have shown at the edge. A mark that reappears through fresh paint on a plaster wall has usually been fed for longer than it looks.
Where it hides in an older New Jersey house
Behind paneling in a basement finished in the 1970s or 1980s, where framing was set directly against a foundation wall with no gap and no vapor 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.
That shared basement is the single most common finding in the two- and three-family belt: Irvington, East Orange and much of Elizabeth are built on it. Nobody living above the stair goes down there between tenancies, so a slow problem gets years rather than months, and the first person to report it is usually whoever moved in last.
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 New Jersey
If there is water in the home right now, that changes the priority: start here instead.