Guide

Signs of Mold in Your Home

Signs you can see or smell

• A musty, earthy smell, especially in a basement, closet, or around a window
• Dark spots or discoloration on drywall, grout, or wood, particularly near a known leak
• Peeling, bubbling, or cracking paint, which usually means moisture is trapped underneath
• Warped or soft drywall or wood flooring
• Condensation on windows or pipes that shows up repeatedly, not just once after a hot shower
• Water stains on a ceiling, even old ones, since the moisture that caused them can still be present

Signs in how you feel

Mold exposure symptoms overlap heavily with allergies: sneezing, a runny or stuffy nose, itchy or watery eyes, coughing, and skin irritation. The clue that points toward mold specifically is a pattern, symptoms that show up or get worse indoors at a particular property and ease up somewhere else. Household members with asthma or existing respiratory conditions are usually the first to notice.

Where mold hides in older Adams County homes

Behind finished basement walls, under carpet padding near an exterior wall, inside HVAC ductwork, under sinks, and around old window frames are the usual hiding spots. Older stone and brick foundations common throughout Gettysburg's historic district often have less effective moisture barriers than modern construction, which means a leak or chronic dampness can spread further behind a finished surface before it becomes visible. See our guide on historic homes and mold for more on why this area sees it more often.

Where it hides in an older Adams County house

Visible growth on a wall is the easy case and the least common one. Most of what we get called about was found by smell or by a renovation, because the growth was somewhere nobody looks.

• Behind finished basement walls, in the cavity between a damp masonry wall and the drywall someone added
• Under carpet padding, which is a sponge and holds water long after the carpet feels dry
• Inside wall cavities below a slow plumbing leak, often a considerable distance from the leak itself
• On the underside of the subfloor above a crawlspace with exposed soil
• On the roof deck in the attic, usually worst on the north slope. See attic mold
• Behind and under bathroom tile where the grout or the pan has failed
• Inside the HVAC system at the evaporator coil and drain pan. See HVAC and mold
• Behind furniture pushed flat against an exterior wall, and in closets on exterior walls
• Under and behind kitchen and bathroom cabinets after a supply line has wept
• Around window frames where condensation collects in winter

The smell is a real signal, not a vague one

That musty, earthy smell is produced by actively growing mold. It is evidence of something growing right now, not of something that happened once. A basement that smells musty but looks clean almost always means the growth is hidden rather than absent, and it is worth opening an inspection hole rather than buying an air freshener.

A smell that comes and goes with the weather points at humidity and condensation. A smell that appears within a minute of the HVAC starting and fades when it stops points at something in the airstream. A smell concentrated at floor level over a crawlspace points downward, because air moves upward through a house and a meaningful share of ground-floor air came through that crawlspace first.

Things that look like mold and are not

Efflorescence

White, crystalline, often fluffy deposits on masonry. It is salt left behind when water moves through the wall and evaporates, and it will dissolve if you wet it, which mold will not. It is not mold. It is, however, proof that water is moving through that wall, so it is worth acting on for a different reason.

Soot and ghosting

Dark deposits around supply registers, on ceilings above a fireplace, or in stripes tracking the framing behind drywall. That is particulate settling where a surface is cooler, not growth.

Water staining

A brown or tan stain with a defined tide line is a record of water that has already been and gone. Worth investigating, not automatically mold.

Mildew on a shower surface

Surface growth on grout and caulk in a bathroom is common, is not a structural problem, and is usually a cleaning and ventilation issue rather than a remediation job. See bathroom mold.

Symptoms, stated carefully

Mold exposure is associated with respiratory irritation, and people with asthma or allergies, and people who are immunocompromised, are more affected. The honest version is that symptoms are non-specific: a cough, congestion, irritated eyes and a sore throat describe a great many things.

The pattern worth paying attention to is not the symptom itself but where it occurs. Symptoms that improve when you leave the house for a few days and return when you come back, or that track with one particular room, are telling you something about the building. Symptoms alone are not a diagnosis, and no legitimate contractor should be diagnosing anyone. What we can do is find the water and the growth.

When to look harder

• A musty smell anywhere, at any strength
• Any water event in the past that was not dried within about two days. See mold after flooding
• Condensation on the inside of windows in winter
• Floors above a crawlspace that feel cold, soft or springy
• Peeling paint, bubbling wallpaper or a bulge in drywall near floor level
• Insulation fallen away from a subfloor or out of an eave
• A history of a slow leak that was repaired without anyone opening the wall

Next: basement mold, humidity and dew point, or what the work involves.