How to remove mold from my basement

You can scrub surface mold off a hard wall or floor with soap and water, but it grows right back unless you fix what feeds it, which is moisture. Mold needs water to live. Take the water away and it has nothing to grow on. So real mold removal in a basement is two jobs. Clean what is there. Then keep the basement dry so it cannot come back.

Here is the order we use when we walk a New Hampshire basement.

First, clean the visible mold

For a small patch on a hard surface, like a painted wall or a concrete floor, you can handle it yourself. Wear gloves and a mask. Scrub with soap and water. Let it dry all the way. The EPA says hard surfaces under about 10 square feet are usually fine for a homeowner to clean, and that you should not paint or caulk over mold before you clean it (epa.gov, mold guidance). If it has spread wider than that, or it is in soft material like drywall, carpet, or stored boxes, throw that material out. Porous material holds mold deep where a brush cannot reach.

A word on bleach. You do not need it on every job, and it is not your only option. Soap and water does the cleaning. The bigger fix is drying the room out.

Then fix the moisture, or it comes back

This is the part most people skip, and it is why mold keeps returning.

Basement moisture usually has a source. Water pools against your foundation because the soil out there is disturbed backfill. That is the loose fill that got put back when the house was built. It drains slowly and holds water against the wall. NH frost heave can push walls in over the years too. Add humid summer air sitting in a cool basement, and you get the damp that mold loves.

Drying a basement for good is not a fan in the corner. The fix we install is the Forever Dry System: a full-perimeter interior drainage channel set at the floor wall joint, a sump pump (1/2 hp per 120 feet of drain) to carry water out, a 12-mil vapor barrier on the walls to block dampness coming through the concrete, and a dehumidifier to pull the humidity down. That combination keeps the room dry, so mold has nothing to feed on. The system is 100% guaranteed to be dry for life, and the guarantee is transferable (conditional).

What does a waterproofing system run? It depends on the size of your basement, how much drain you need, and whether the floor has to be cut. We price it after a free inspection: $3,000 to $30,000. Crawl space encapsulation is a different scope and a different number: $3,000 to $25,000.

You may not need everything

If your only problem is a small mold spot and the basement is otherwise dry, you do not need a full waterproofing system yet. Clean the spot, run a dehumidifier, watch it through a wet spring. If it stays dry, you are fine. If the damp keeps coming back no matter what you do, that is the signal something is letting water in, and that is when the drainage fix earns its keep.

One thing we do not do, on purpose: dig up your yard to waterproof from outside. In our field experience that fix tends to fail in a couple of years, and you have torn up the landscaping for it. The durable fix is interior drainage that handles the water once it reaches the wall.

A note on basement air

Mold and a musty smell often ride together because both come from humidity. If you are also smelling that damp basement odor, the cure is the same. Get the moisture down. A sealed, dehumidified basement smells better and stays mold-free because the air no longer holds the water mold needs.

If your basement floods or backs up, your homeowners policy may or may not cover the cleanup, since flood and seepage are often treated differently. Check your own policy. The Insurance Information Institute (iii.org) explains how water damage coverage typically works.

Ready to find the source?

We will come look, find where the water is getting in, and tell you what it actually needs. The inspection and estimate are free, and you get a quote within 24 hours.

Call us at 603-610-1770 or book your free inspection. Trusted by 5,000+ homeowners across New England, 4.9 stars on Google, BBB A+ accredited.

See how we keep basements dry on our basement waterproofing page, read about crawl space services, and check the 603 guarantee.

Related questions

Will mold come back after I clean it? Yes, if the basement is still damp. Mold needs moisture to live. Clean the surface, then keep the room dry with drainage and a dehumidifier so it has nothing to grow on.

Is basement mold dangerous? It can bother people with allergies or asthma, and a large amount should be handled carefully. The EPA recommends cleaning small areas yourself and getting help for anything larger than about 10 square feet (epa.gov).

Does a dehumidifier alone stop basement mold? It helps a lot if water is not actively coming in. If you still get pooling or wet walls after rain, the dehumidifier is fighting a losing battle, and you need to stop the water at the source with interior drainage.

Do you handle the musty basement smell too? Yes. The smell and the mold both come from humidity, so the same dry-the-room fix takes care of both.