How to Remove Mold From Inside Walls

1. Contain Work Area

   Use plastic sheeting and painter's tape to block off doorways leading to other areas. Tape plastic sheeting on the floor in front of the wall.

2. Shut off Electricity and Water

   At the electric service panel, shut off circuit breakers to any suspected circuits running through the wall. If water lines run through the wall, shut off the water at its main shut-off valve.

3. Identify Area of Mold

   Mark off the general area of the mold either with a pencil or with painter's tape. Use the stud finder to identify the positions of wall studs in the area.

4. Remove Drywall

   With the prybar, gently chip into soft, moldy drywall and pull it off. Immediately place all moldy drywall into large contractor's bags. Keep expanding the area until you reach dry, solid drywall that has no mold on it.

5. Remove Insulation

   Carefully pull the insulation away from the staples that attach it to the wall studs. Roll up moldy insulation and place it in the bags. Continue until you reach insulation that has no mold on it.

6. Assess Mold

   With moldy drywall and insulation bagged and removed, shine a bright work light inside the wall. Mold will often remain on hard surfaces: studs, sill plates, headers, and the back of the siding. Unless these materials are severely damaged, they can be cleaned and the mold can be encapsulated.

7. Dry out Area

   If the area is wet, leave it open to dry it out. Directing fans set to low will speed up the drying.

8. Vacuum Mold

   With the HEPA-filtered shop vacuum, thoroughly vacuum all of the mold. Vacuum the rest of the wall cavity, too, picking up dust, spider webs, and rodent droppings.

9. Disinfect Mold

   With the one-gallon garden pump sprayer containing the mold biocide, completely spray down all of the moldy areas. Fully soak the materials but not so much that the fluid drips onto the floor.

10. Dry out Area

    Let the area dry out. No moisture should remain on any of the surfaces.

11. Encapsulate Mold

    With a brush or roller, paint the area with the fungicidal mold encapsulant. After the first coat has dried, apply a second coat of mold encapsulant.

12. Close up Walls

    Insulate the wall, if necessary. Hang drywall. Tape the seams, apply drywall compound (mud), and sand smooth. Apply drywall primer, then paint with interior latex paint.

    Tip

    Fiberglass insulation is not recommended for moisture-prone areas like exterior basement walls. Slab foam or spray foam insulation are effective alternatives to fiberglass in these areas.

Troubleshooting Removing Mold From Inside Walls

After cleaning, the mold still looks like it's there.

Mold can be very difficult to completely scrub away. But as long as the mold has been properly disinfected, there is no need to remove all visible mold inside of the walls. The walls will eventually be closed up with drywall. Also, the encapsulating coating will cover up much of the visible mold.

Chemicals are not preferred.

Killing mold naturally is just as effective as killing mold with powerful chemicals—it just takes longer. Ventilation and light are enough to kill mold. You'll need to have the wall open long enough for this method to take effect.

Fungicidal coating did not fully kill the mold.

Fungicidal mold encapsulants are meant to aid, not replace, the core method of killing the mold. They also help with some limited ongoing mold problems. Do not use only a fungicidal mold encapsulant on the assumption that it will both kill and encapsulate the mold.

When to Call a Professional

How Extensive Is the Mold?

Mold damage up to 10 square feet is manageable by most do-it-yourselfers. As the size increases, the job becomes exponentially unwieldy. The EPA recommends that mold patches exceeding 10 square feet be removed by professionals.

What Is Your Schedule?

Mold remediation companies often can remove mold in a matter of days, not weeks. Unless you can afford to spend a week or two on the project, have the pros do it.

What Time of Year Is It?

Opening up drywall and removing insulation in the winter is enough to challenge even the most robust HVAC system. By doing the job rapidly, professionals can limit your home's exposure to the elements.

What Is the Source of the Moisture?

If the source of the moisture that caused the mold growth has not yet been determined and repaired, hire a professional to diagnose and fix the water issue.

Is This Part of a Home Sale?

Homebuyers who request that the seller remediate the mold prior to purchasing the home usually want to see professional work. Equally importantly, they want to see an invoice reflecting that the work has been done. If you do the work yourself and it doesn't pass the second inspection, the home sale comes to a halt until the work is complete.