How to Get Rid of Mold: What Actually Works and What Doesn't

There is one principle behind every mold job, and most failed attempts ignore it: mold is the symptom, water is the cause. You cannot get rid of mold by killing it, because spores exist in virtually all indoor air and will settle again. What you can do is take away the water it needs to grow. Remove the moisture and mold has nowhere to go. Leave the moisture and it returns within 24 to 48 hours, no matter what you sprayed on it.

That is why the first step in this guide is not cleaning. It is finding the water.

What Should You Do First?

Identify the moisture source before you touch the mold. There are only a few possibilities, and they lead to completely different fixes:

• A leak — plumbing, roof, window seal, or appliance. Usually localised, often worst after rain or use.
• Condensation — warm humid air meeting cold surfaces. Appears on windows, external walls, and in unheated or unventilated rooms, worst in winter.
• High indoor humidity — from showering, cooking, unvented dryers, or drying laundry indoors. Produces mold in several places at once rather than one spot.
• Groundwater or drainage — basements and crawl spaces, worst after heavy rain or snowmelt.

If you clean without answering this question, you are booking yourself a repeat job.

Then measure the area. The EPA’s general guidance is that patches under roughly 10 square feet are usually within a homeowner’s reach, and larger areas warrant professional remediation with proper containment. Be honest about what you can see versus what might extend behind a surface — mold visible at the edge of a skirting board or around a ceiling stain frequently continues into the cavity.

What Can You Clean Yourself?

For a limited area with a known and fixable moisture source, on hard surfaces:

Wear an N95 respirator, gloves, and eye protection — cleaning releases more spores than leaving mold undisturbed, so the protection matters most while you work. Contain the room: close internal doors, turn off central heating and air conditioning so you are not distributing spores through the ducts, and vent air out of a window rather than blowing it around the house.

Scrub hard, non-porous surfaces — tile, glass, metal, sealed plastics, sound painted surfaces — with detergent and water or a commercial antifungal cleaner. The scrubbing is the active ingredient. A surface that has been sprayed and left is not cleaned.

Accept that porous materials often cannot be saved. Mold grows into the material rather than sitting on it. Carpet and underlay, insulation, ceiling tiles, and drywall that is soft, stained through, or still musty after cleaning need to be removed and replaced. Repeatedly cleaning a material that has mold growing inside it is the second most common way people waste time on this.

Dry the material, not the surface. Fans and a dehumidifier, running for days rather than hours, until the material itself is dry. This is the step people cut short, and it is why mold reappears in the same place a fortnight later.

What Doesn’t Work

Being direct about this saves people money:

Painting or sealing over mold. Paint covers growth without removing it, and mold grows through or under it. Mold-resistant paint is for preventing growth on a clean, dry surface, not for burying an existing problem.

Bleach as a universal answer. Fine on glass and tile. On drywall, plaster, or bare timber, bleach is mostly water — it removes the colour while the moisture soaks into the material. A patch that looks clean and smells musty has not been fixed.

Air purifiers, ozone generators, and fogging “mold bombs”. These treat air, not materials. A HEPA purifier may reduce airborne spores and ease symptoms while a real repair happens, but it will not touch a colony on a damp wall. Ozone generators carry their own respiratory health warnings and still do not remove growth.

Testing as a substitute for fixing. If you can see the mold and you know where the water came from, a test usually confirms what you already know and postpones the repair.

Cleaning without ventilation or protection. Disturbing mold without an N95 and airflow spreads spores through the house and exposes you to the highest concentrations of the whole job.

When Do You Need a Professional?

Not every mold problem needs paying for, and we would rather be straight about which do:

• The affected area exceeds roughly 10 square feet, per EPA guidance.
• The mold is inside a wall cavity, under a floor, or in the HVAC system, where removing it means opening up the structure and containing the work.
• It followed sewage backup or flood water, which brings contamination beyond mold alone.
• You can smell mustiness but cannot find growth, which means it is somewhere you cannot access.
• It keeps returning after genuine cleaning and drying, indicating an unresolved structural or thermal cause.
• An occupant has asthma, a mold allergy, or a compromised immune system, or there are infants or elderly residents, where disturbing mold carries greater risk.
• You need documentation for a landlord dispute, an insurance claim, or a property sale — where an independent assessment and clearance testing have real value.

A professional job should follow the IICRC S520 standard: containment, negative air pressure, removal of unsalvageable porous materials, HEPA filtration, drying to a verified moisture target, and independent clearance verification afterwards. One thing to insist on — the company that does the remediation should not be the one certifying its own clearance test. An independent assessment protects you.

Worth knowing if you are in Maryland or New Jersey: neither state currently licenses mold professionals, so a “licensed mold specialist” claim may refer to a general contractor registration rather than any mold-specific credential. See our guide on verifying whether a mold inspector is licensed for how to check what a credential actually means in your state.

How Do You Keep It From Coming Back?

Hold indoor relative humidity between 30 and 50 percent and verify it with a hygrometer rather than guessing. Run extractor fans during and for around 20 minutes after showering and cooking. Vent tumble dryers outside and stop drying laundry on radiators. Fix leaks within 24 to 48 hours — that is the window before mold establishes on wet material. Improve airflow in closed, cold rooms and keep furniture and curtains off external walls. Deal with drainage — gutters, downpipes, and ground falling away from the building — before the basement tells you about it.

Related Guides

• The Mold Remediation Process — what a professional job actually involves, step by step
• Mold Remediation Cost — what drives the price and where estimates go wrong
• Is Your Mold Inspector Licensed? — what credentials mean state by state
• Mold on Windows — the most common condensation case
• Black Mold Health Effects — what the evidence supports
• Clearance Testing After Remediation — verifying the job was done