Remove Mold From Drywall and Walls: Clean It or Cut It Out?

You can only remove mold from drywall by cleaning when it is a light film on a painted surface over solid, dry board. Once mold has grown into the paper facing or the gypsum, or the drywall has been wet long enough to swell or crumble, the EPA's guidance is to cut it out, bag it and replace it. In both cases, find and fix the water source first, or the mold will grow back. For larger jobs, see our mold remediation overview.

Why drywall is hard to clean

Drywall is a gypsum core wrapped in paper. Paper is exactly what mold likes to eat, and the material soaks up water like a sponge. The EPA lists drywall among the common places for mold to grow, including on the back side of drywall where you cannot see it (EPA, A Brief Guide to Mold, Moisture and Your Home). The CDC also notes that mold can grow in paint, wallpaper, insulation and drywall (CDC).

That is why the EPA's remediation table treats drywall differently from hard surfaces. For tile, metal or plastic, it lists damp-wiping with water and detergent. For wallboard (drywall and gypsum board), it lists only two methods: HEPA vacuuming after the material is thoroughly dried, and discarding the damaged material (EPA Table 2). In other words, wiping is not listed as a fix for moldy drywall.

Clean it or cut it out?

Use this as a starting point. When in doubt, cutting out is the safer choice, and drywall is inexpensive compared with recurring mold.

The EPA's water-damage table says drywall that got wet with clean water may be dried in place only if there is no obvious swelling and the seams are intact; otherwise remove, discard and replace it, and ventilate the wall cavity if possible (EPA Table 1). After floods, Nebraska Extension guidance has been to remove drywall two feet above the wet line (University of Nebraska-Lincoln). Local practice varies with how high water wicked up the wall.

How to clean mold off painted walls (small, surface-only patches)

This is for small, surface-level spots on a sound wall. The EPA says that if the moldy area is less than about 10 square feet, most people can handle it themselves (EPA).

1. Fix the moisture. Look for a leak, condensation on an exterior wall, or a humid room. The EPA says controlling moisture is the key to controlling mold (EPA).
2. Protect yourself. Wear an N-95 respirator, gloves and goggles (EPA).
3. Use as little liquid as possible. Wipe with a cloth barely dampened in a detergent solution. Soaking drywall can damage the paper and feed more growth.
4. Dry the wall right away with a fan or dehumidifier.
5. Bag the cloths and throw them out.
6. Watch the spot. If it returns within weeks, the mold is in the board.
7. Repaint only once it is clean and dry. The EPA says not to paint or caulk moldy surfaces, because paint applied over mold is likely to peel (EPA). Mold-resistant paint helps prevent new growth on a clean wall; it does not fix existing mold.

If you choose bleach for a painted surface, the CDC says use no more than 1 cup of bleach per gallon of water, open windows, and never mix bleach with ammonia or other cleaners (CDC).

How to remove moldy drywall

Cutting out drywall disturbs mold, so the work is more about containing dust than about cleaning. For small sections a careful homeowner can do it; for larger areas the EPA recommends containment and stronger protection, which is professional territory. The CDC notes that a task like ripping out moldy drywall may call for a half-face or full-face respirator (CDC).

1. Shut off the HVAC serving that room so spores are not blown through the house. The EPA says not to run an HVAC system you suspect is contaminated (EPA).
2. Seal the area with plastic sheeting over doors and vents.
3. Lightly mist the surface to keep dust down. Do not soak it.
4. Cut well past the visible growth. Mold on the face often extends further on the back. Check for wiring and plumbing before cutting.
5. Bag pieces inside the work area. The EPA's method is to seal moldy materials in plastic bags before removing them from the containment area (EPA guide, PDF).
6. Inspect the cavity. Look at studs, insulation and the back of the opposite wall. Wet insulation is replaced, not dried; the EPA lists discard and replace for both cellulose and fiberglass insulation (EPA Table 1).
7. Clean and dry the framing. HEPA vacuum the area after it is dried (EPA). Before closing the wall, wood should be completely dry; UNL guidance cites a moisture reading under 16 percent (UNL).
8. Rebuild with new drywall, tape, primer and paint.

Avoid dry sanding moldy drywall or using a shop vacuum without a HEPA filter, both of which spread spores. The EPA also says wet vacuums should not be used on porous materials such as gypsum board (EPA).

What not to clean mold with

• Never mix chemicals. Bleach with ammonia releases toxic fumes (EPA), and bleach with vinegar creates chlorine gas (Poison Control).
• Don't rely on killing mold. The EPA says it is necessary to remove mold, not just kill it, because dead mold is still allergenic. It does not recommend bleach as a routine remediation step (EPA).
• Don't soak drywall. Saturating it with any cleaner, including vinegar, adds water to a material that is already the problem. Our vinegar and mold guide covers what vinegar can and cannot do.
• Don't paint over it. Covering mold hides it without stopping it.

How to detect mold inside walls

Mold in house walls is often found by its effects before you see it:

• A musty smell. The EPA says a moldy odor suggests mold is growing in the building and should be investigated, even if it is not visible (EPA).
• Stains, bubbling or peeling paint, especially low on walls or below windows and bathrooms. See signs of water damage.
• Soft or swollen drywall near baseboards.
• A known leak behind the wall, such as a supply line, drain, or window.
• Moisture meter readings that stay high after the room should be dry.

A small inspection hole is the most direct check. The CDC does not recommend routine mold testing, because sampling cannot tell you whether someone will get sick, and its advice is to remove the mold and prevent new growth (CDC). If you need an assessment for a hidden problem, our mold testing and inspection guide explains the options.

Health and safety

The CDC says mold can cause a stuffy nose, sore throat, coughing or wheezing, burning eyes or skin rash in some people, and people with asthma or mold allergy may have severe reactions (CDC). If you or someone at home has symptoms, see a doctor, and let someone else do the tear-out. Our mold exposure symptoms guide has more.

When to call a professional

Call for professional mold remediation if the moldy area is larger than about 10 square feet, the wall got wet from floodwater or sewage, mold is in the HVAC system, or the source of the water is unknown. Professionals follow standards such as the IICRC S520 Standard for Professional Mold Remediation, including containment and post-remediation checks. If the drywall is still wet from a recent leak, drying it within 24 to 48 hours may prevent mold altogether (EPA); see water damage restoration and our guide to water-damaged drywall.

Getting help

Flood Rescue Pros is a free service that connects homeowners with independent local water damage and mold restoration companies. We do not do the work ourselves. If you would like a local company to look at mold on your walls, get help now or start from our locations page.

Frequently asked questions

Can you remove mold from drywall, or must it be replaced?

Light surface spots on sound, painted drywall can sometimes be wiped and dried. The EPA's remediation table lists only HEPA vacuuming after drying and discarding for moldy wallboard, so drywall with mold in the paper or core should be replaced.

Is vinegar good to kill mold on drywall?

Vinegar is a common household cleaner, but the EPA's guidance focuses on removing mold rather than killing it, and soaking drywall with any liquid adds moisture to the problem. Never mix vinegar with bleach.

How do you detect mold inside walls?

Watch for a musty smell, stains, bubbling paint, soft drywall or a known leak. A moisture meter and a small inspection hole confirm it. The EPA says a moldy odor should be investigated even when no mold is visible.

What should you not clean mold with?

Never mix bleach with ammonia or vinegar. Avoid soaking porous drywall, dry sanding moldy material, or painting over mold.

How far past the mold should you cut drywall?

Cut beyond the visible growth, because mold on the back of the board often spreads further than on the face. After floods, Nebraska Extension has advised removing drywall two feet above the wet line.

Key facts

• The EPA's remediation table lists only HEPA vacuuming after drying and discarding for moldy drywall, not wiping.
• Clean-water-wet drywall may be dried in place only if it is not swollen and the seams are intact, per EPA.
• Most people can handle mold areas under about 10 square feet; larger areas need containment and professional work.
• Never paint over mold, and never mix bleach with ammonia or vinegar.
• A musty smell, stains, bubbling paint or soft drywall can point to mold inside walls.
• Fixing the moisture source and drying within 24 to 48 hours is what prevents mold from returning.