How to Get a Musty Smell Out of a Basement

That musty smell is a message. Somewhere in your basement, moisture is sitting where it shouldn't — on a wall, in the air, in a box of old blankets — and mildew is living on it. So the fix isn't a candle or a plug-in. It runs in order: find where the moisture is coming from, clear out the damp things you don't need, clean the mildew-stained surfaces, and then dry the air with a dehumidifier so the dampness doesn't build back up. Do it in that order and the smell goes with it. For the cleaning step, we make Mold & Mildew Warrior, a plant-based cleaner that removes mildew stains and musty odors from surfaces — no bleach, which matters in a room with almost no airflow. But no cleaner fixes a wet basement. Start with the moisture.

Why basements get musty

Basements are cool, and cool surfaces collect condensation. Concrete and block walls can wick moisture straight in from the ground. Air barely moves down there, so nothing dries out on its own. And most basements are full of cardboard, fabric, and carpet — materials that soak up damp and hold it.

Mildew settles in on all of it, and the smell you notice at the top of the stairs is the result. None of that is a judgment on your housekeeping. It's physics working against you in the one room of the house with no breeze.

Getting the smell out, step by step

1. Find the moisture

Walk the basement slowly, ideally a day or two after a good rain. You're looking for:

• Damp patches or water lines on the walls or floor
• Downspouts that dump water right beside the foundation, or ground that slopes toward the house
• Cold water pipes or ductwork sweating in summer
• Slow drips at the water heater, washer connections, or any plumbing
• A white, chalky residue on concrete — that's minerals left behind by water migrating through the wall

Pick up a cheap hygrometer while you're at it. If the reading sits above 60 percent, the air itself is part of the problem, not just a leak.

2. Clear out the damp material

Cardboard is a sponge. So are old rugs, upholstered furniture, and boxes of clothes. If something smells musty and can't be fully washed and dried, let it go. Move what you're keeping into plastic bins with lids. Old carpet laid straight on concrete is a common culprit — if it smells, it's holding moisture against the floor.

3. Air it out

On a dry day, open the windows or the door at the top of the stairs and set a fan blowing stale air out. Even a few hours of real air movement makes a difference before you start cleaning.

4. Clean the mildew-stained surfaces

A lot of the musty odor lives right in the mildew staining on walls, floors, and whatever's been sitting against them. This is the step we make a product for: Mold & Mildew Warrior is a plant-based liquid cleaner for mildew-stained and musty surfaces. The active ingredient is citric acid at 8.5 percent; the rest is water, ascorbic acid (vitamin C), and citrus pulp. No bleach, no harsh chemicals — a real consideration when you're working in a room where fumes have nowhere to go.

One jug is 128 ounces, which is the right scale for basement walls and floors rather than a spray bottle's worth. It's $42.75, made in the USA, and ships free in the US.

To be straight with you about what it does: it removes the stains and the odors they carry. It does not fix moisture. That part is on steps 1 and 5.

If pets share your house, keep them out of the basement while you clean and off the surfaces until everything is dry. We wrote a separate guide on cleaning mold and mildew stains when you have pets if that's your situation.

5. Dry the air, and keep it dry

This is the step that makes the others stick. A dehumidifier sized for your square footage, set somewhere around 50 percent, running through the humid months, is what keeps a basement from drifting back toward damp. Empty the tank regularly or run its hose to a drain so it never sits full and shut off.

Then handle whatever you found in step 1: extend the downspouts, clean the gutters, wrap the sweating pipes, fix the drip. A dry basement doesn't smell musty. That's the whole game.

When it's more than a smell

Surface cleaning is for surface problems. If mold covers a large area, keeps coming back after you've cleaned and dried the space, or you suspect it's inside walls, insulation, or ductwork — or there's ever standing water — stop and bring in a professional. That's a moisture problem in the structure, and no jug of anything is the right answer to it.

FAQ

Why does my basement smell musty when I can't see any mold? Damp cardboard, fabric, and carpet can smell musty long before any staining shows. Mildew also hides behind stored boxes, under stairs, and on the back sides of furniture pushed against cool walls. A hygrometer reading and a good clear-out usually reveal the source.

Do I need bleach to get rid of the musty smell? No. Bleach fumes are rough in a room with little ventilation, and mildew stains and odors can be removed without it. That's why we make Mold & Mildew Warrior with citric acid instead of bleach.

What humidity level should a basement be? Around 50 percent relative humidity is a common target. Once the air sits much above 60, damp materials stop drying out. An inexpensive hygrometer takes the guesswork out of it.

How long until the smell is gone? There's no fixed timeline — the smell fades as the space dries out and the stained surfaces come clean. If it returns, moisture is still getting in somewhere. Go back to step 1 rather than cleaning the same spot again.

Is the cleaner safe to use around kids and pets? "Safe" is a word we're careful with, so here's what we can tell you plainly: it's made without bleach or harsh chemicals, the ingredient list is short enough to read (citric acid, vitamin C, citrus pulp, water). Sensible practice is still sensible: keep kids and pets out of the room while you work, keep them off surfaces until dry, and rinse anything food will touch.

The short version

Find the moisture. Clear out what's holding it. Clean the stained surfaces. Dry the air and keep it that way. That order, every time.

When you get to the cleaning step, Mold & Mildew Warrior is the product we make for exactly this job — one gallon, plant-based, no bleach, free shipping in the US. And if you'd rather hear it from someone besides us, you can read what customers have said on our testimonials page.