Mold in closets and storage: still air and what cleanup costs

Why closets grow mold

A closet is a small room with the door closed, packed with things that hold water, against the coldest wall in the house.

Still air is the first cause. Heated rooms move air with registers, people, and open doors, and a closet gets none of that. The air inside sits, and the humidity in it has nowhere to go.

The exterior wall is the second. A closet on an outside wall, especially a corner closet, has a wall that gets cold in winter. Warm house air that seeps in through the door carries vapor, and the vapor condenses on the cold wall and the cold corner near the ceiling or the floor. Clothes and boxes stacked against it block what little warmth the room gives it, and the wall stays cold, damp, and dark.

Contents are the third. Cardboard, paper, leather, cotton, and wool all absorb humidity from the air and hold it. A closet full of boxes and coats is a closet full of damp material. Carpet in a closet on a slab holds ground moisture in the pad.

Plumbing and shared walls add a fourth in some houses. A closet that backs onto a shower, a water heater closet, or an HVAC closet shares a wall with something wet. A slow leak on the other side shows up first on the closet side, because that side is dark and nobody looks.

Signs you can check in the closet

The first sign is usually the smell on the clothes. Coats, shoes, and anything stored on the floor pick up a musty odor before anything is visible.

Empty the closet and look with a flashlight.

• Gray, white, or green fuzz on leather shoes, belts, bags, and cardboard boxes.
• Dark spotting on the exterior wall, usually in the upper or lower corner, and behind where the shelves or the rod were.
• Carpet that is damp at the back wall, or a dark line where the carpet meets the baseboard.
• Staining or softness on the drywall of the wall shared with a bathroom or a utility closet.
• Condensation on the wall or the ceiling corner on a cold morning.
• Paint that bubbles or peels in one area.

Press the wall where the spotting is. Firm drywall with surface spotting is a cleaning job. Soft drywall has growth in the paper and comes out. A damp carpet at the back of a closet on a slab points at ground moisture, and a stain on a shared wall points at a leak on the other side.

What happens if it waits

Contents go first. Leather, cardboard, paper, and fabric that have grown mold are hard to clean and mostly get discarded. Photographs and documents stored in a damp closet are the loss people regret most.

The wall is next. Surface spotting on paint works into the drywall paper, and drywall with growth in the paper comes out. Carpet and pad in the closet follow. If the cause is a leak on the other side of a shared wall, the growth is already in the cavity, and the closet is the visible edge of a behind walls job.

Air quality is modest for one closet and larger for a closet that opens onto a bedroom. The smell lands on everything stored there, and mold can irritate people who are sensitive to it.

Buyers open closet doors, and a musty closet reads as a damp house.

What closet remediation involves

Contents come out first. The crew or the homeowner sorts them: hard, non-porous items get cleaned, washable fabric gets washed, and porous items with visible growth get bagged. A remediation company usually leaves the sorting to the homeowner and prices the room.

The closet is small, so containment is simple: plastic at the door and negative air inside. The crew HEPA vacuums every surface, cleans the hard surfaces, and treats the wall with an antimicrobial. Surface spotting on sound drywall gets cleaned and sealed. Drywall with growth in the paper gets cut out past the stain, along with any wet insulation behind it, and the framing gets cleaned, treated, and dried. Carpet and pad come out when they are wet.

The moisture fix depends on the cause. A cold exterior wall gets insulation added if the cavity is empty, and the closet gets air movement. A slab moisture problem gets the carpet replaced with a hard floor. A shared-wall leak gets a plumber. The bathroom mold page covers the shower side of a shared wall.

Drywall replacement, finished and painted, is priced on its own at $1.00 to $2.10 per square foot.

What moves the closet price

The band shown above, $500 to $1,500, is the small-area band. The engine applies it to closets and storage rooms because the scope is one wall plus the contents, which is the same visible, contained, accessible shape as a small bathroom job. This Old House prices that small-area scope at $500 to $1,500.

Within the band, the job moves on whether the drywall comes out. Cleaning and sealing a wall with surface spotting is the bottom. Removing one wall of drywall and the carpet, treating the framing, and replacing the drywall is the top. Remediation prices at $10 to $25 per square foot of affected surface, and a closet wall is a small number of square feet.

The conditions that turn a closet into a wall job are a shared wall with a shower or a water heater, a stain that runs under the baseboard into the next room, a moisture meter that reads wet across the wall rather than in one spot, and growth that continues behind the drywall when the first piece comes out. Any of those moves the job to the walls band at $1,000 to $12,000.

Contents volume moves the price when the company handles them. A walk-in closet full of boxes is more labor than a hall closet with coats.

A finished basement storage room is a basement job. See the basement mold page.

Get a planning range from the estimate tool. These are planning ranges from national data. An independent remediation company confirms scope and price on site.

Keeping closets dry

Move air through the closet. A louvered door, a door left open, or a small gap at the bottom of the door keeps the air from going still.

Keep storage off the exterior wall. Wire shelving instead of solid shelves lets air move. Leave space between the clothes and the wall.

Store in plastic bins with lids instead of cardboard, and keep bins off a carpeted floor on a slab.

Hold the house humidity in the EPA range, below 60 percent and ideally between 30 and 50 percent. A small dehumidifier in a damp bedroom protects the closet in it.

Empty and inspect the closet each spring. A musty smell on the coats is the earliest warning you get. More in preventing mold from coming back.