The short answer
For small patches on painted walls or tile, fix the moisture source first, then clean with detergent and water, disinfect with a bleach solution or EPA‑registered mold cleaner, and dry thoroughly. If mold has penetrated porous materials like drywall or ceiling tiles, cut out and replace the affected sections. If the affected area is larger than about 10 square feet, consider hiring a professional mold remediation contractor.
Why this works
Mold needs moisture and organic material to grow. Cleaning removes the colonies; disinfection knocks back remaining spores; thorough drying and moisture control prevent regrowth. Non‑porous surfaces (tile, sealed masonry) can usually be cleaned. Porous materials (unsealed drywall, paper-faced insulation) often need removal because mold roots can penetrate below the surface.
Tools and materials
- PPE: N95 or better respirator (P100 for heavy growth), nitrile gloves, goggles, disposable coveralls or old long sleeves
- Containment: plastic sheeting, painter’s tape, box fan for window exhaust
- Cleaning: bucket, microfiber cloths, non‑scratch scrub pads, soft brush, pump sprayer or spray bottle
- Chemicals: dish detergent, household bleach, white vinegar or 3% hydrogen peroxide, or an EPA‑registered mold/mildew cleaner
- Removal/repair (if needed): utility knife, oscillating multi‑tool with drywall blade, pry bar, contractor bags, HEPA shop vac, replacement drywall/insulation, joint compound, sanding sponge, mold‑resistant primer and paint
- Drying/control: dehumidifier, moisture meter (helpful), towels
Safe cleaning solutions
Bleach (hard, non‑porous surfaces): 1 cup (240 mL) household bleach per 1 gallon (3.8 L) water.
Vinegar (porous or semi‑porous surfaces): Use full strength; dwell 60 minutes.
Hydrogen peroxide 3%: Spray undiluted; dwell 10–15 minutes.
Borax: 1 cup per gallon warm water; no rinse needed.
Never mix bleach with ammonia, vinegar, or other cleaners. Provide good ventilation.
Step-by-step: small areas on painted walls or tile (under 10 sq ft)
1) Stop the moisture
- Fix leaks, improve ventilation, and aim indoor humidity below 50%. Run a bath fan or dehumidifier during and after the work.
2) Set up containment and PPE
- Wear your respirator, gloves, and goggles.
- Open a window, place a box fan blowing out, and seal air returns with plastic. Close doors and place a towel at the threshold.
3) Dry dust removal with HEPA
- Lightly HEPA‑vacuum the area and adjacent surfaces to remove loose spores. Avoid a regular vacuum—it can spread spores.
4) Wash
- Mix warm water with a few drops of dish detergent. Wipe or gently scrub the surface with a microfiber cloth or soft brush. Don’t over‑scrub painted drywall—you can fuzz the paper.
5) Disinfect
- On hard, non‑porous surfaces (tile, sealed paint), apply your chosen disinfectant: bleach solution, peroxide, or an EPA‑registered product. Keep the surface visibly wet for the dwell time (10–15 minutes for peroxide; 10+ minutes for bleach).
- For painted drywall with only superficial spots, prefer peroxide or an EPA‑registered cleaner over bleach, as bleach doesn’t penetrate porous materials.
6) Rinse and dry
- Wipe with clean water (skip rinse if using borax to leave a residue) and dry thoroughly with towels and airflow. Use a dehumidifier if humidity is high. Target surface dryness within 24–48 hours.
7) Prime and paint (if needed)
- If staining remains, spot-prime with a mold‑resistant stain‑blocking primer, then repaint with bathroom/kitchen paint containing mildewcide.
Time: 1–2 hours for a small bathroom wall. Cost: $20–$60 in supplies if you already own basic tools.
Step-by-step: if drywall or insulation is affected
Signs you need removal: musty odor persists, drywall is soft/crumbly, staining returns after cleaning, or mold is visible on the back side/inside cavities.
1) Contain and protect
- Suit up (P100 recommended). Seal the work area with plastic and maintain window exhaust.
2) Cut out damaged materials
- Score and remove drywall at least 12 inches beyond visible mold. Bag pieces before carrying out. Remove any affected insulation.
3) Clean the structure
- HEPA‑vac studs and surrounding surfaces. Wipe with detergent solution, then apply peroxide or borate solution and allow to dry. A moisture meter helps confirm wood is under ~15% MC before closing.
4) Close up
- Replace insulation if needed, install new drywall, tape/finish, prime with mold‑resistant primer, and paint. Improve ventilation to prevent recurrence.
Small patch materials: $100–$300. Labor: 3–6 hours for a competent DIYer.
Tips for best results
- Control humidity: Keep indoor RH 30–50%. Use exhaust fans 20–30 minutes after showers.
- Address condensation: Insulate cold pipes/walls and improve air circulation behind furniture.
- Caulk and seal: Re‑caulk tub/shower joints and around window trim to block water intrusion.
- Choose the right paint: Use bathroom‑rated paint with mildewcide for high‑humidity rooms.
- Maintain: Squeegee shower walls; keep doors/curtains open after use to dry faster.
Common mistakes
- Painting over mold without cleaning and drying—stains and odors return.
- Using regular vacuums—spreads spores; use HEPA.
- Over‑reliance on bleach—effective on hard surfaces but poor on porous materials.
- Insufficient drying—mold returns if materials stay damp.
- Mixing chemicals—dangerous fumes; stick to one method.
- Ignoring the source—without fixing leaks or humidity, mold comes back.
When to call a professional
- Affected area larger than about 10 sq ft.
- Mold inside HVAC systems or extensive wall cavities.
- Repeated growth despite your fixes.
- Significant water damage, sewage contamination, or if occupants have respiratory/immune concerns.
- Pre‑1978 paint or unknown joint compound: if demolition/sanding is needed, follow lead‑safe practices or hire a pro.
A qualified remediation contractor will set up containment, use negative air machines with HEPA filtration, remove contaminated materials safely, and verify dryness before rebuild.
Quick tool recommendations
- HEPA shop vac with fine dust filter.
- Oscillating multi‑tool and drywall blade for clean cuts.
- Moisture meter to verify dry‑down.
- Dehumidifier sized for the room (35–50 pint for bathrooms/basements).
Handle the moisture first, then clean or replace strategically, and you’ll stop mold from coming back instead of just hiding it.