The most common type of mold found in homes is mildew. Mildew is a surface mold that grows in warm, damp places like basements, laundry rooms, and shady porches. Mildew begins as a gray or white powdery colony and eventually turns black or brown. To test if the wood is covered with mildew or just dirt, dab the stain with a cotton swab dipped in household chlorine bleach. If the stain lightens or disappears after two or three minutes, it's mildew. If not, it's probably just dirt.
Mildew can discolor and slowly harm wood surfaces but there are much more dangerous molds that can damage the structure of your home. If a fuzzy or slimy black or green mold is visible and the drywall or wood underneath is soft or crumbles, there is irreversible rot and the damaged surfaces must be removed immediately.
How do you determine if you need to hire a professional? If the infestation on wooden surfaces is not black mold and is caught early, you should be able to remove it with household cleaners. For extensive mold problems in poorly ventilated areas like crawlspaces or for anyone with mold allergies or compromised respiratory systems, consider hiring a professional.
Experts recommend that if mold covers 10 or more square feet of the wood surface, a professional remover should take care of the problem. When large areas are affected, the wood may need to be replaced and the infested wood disposed of properly. Local public health departments can offer advice on mold testing and refer you to an expert mold remover.
How Often to Clean Mold Off Wood
At the first sign of mildew or mold, wooden surfaces should be cleaned immediately. For outdoor wood furniture, decks, and siding in humid climates, at least yearly cleanings with a mildewcide is recommended.
How to Clean Mold Off Wood
Before you begin this project, be sure to wear a mask, long-sleeved shirt, and long pants to protect yourself. If possible take the mold-infested wood outside when cleaning to prevent spreading spores to other areas. For interior walls and floors, close doors or use plastic sheeting to shield other areas.
What You Will Need
- Dishwashing detergent
- Chlorine bleach
- Wood stain (optional)
- Protective air mask
- Rubber gloves
- Safety goggles
- Vacuum with HEPA filter
- Soft-bristled scrub brush
- Soft cloth
Put on Protective Clothing
Put on your protective clothing, air mask, and goggles before you begin cleaning. Wear old clothes because bleach splatters will cause stains that cannot be removed.
Vacuum the Mold From the Wood Surface
A vacuum with a HEPA filter is recommended to capture as many mold spores as possible. When all visible mold is removed, empty and clean the dust container or remove the vacuum bag outside and seal the contents in a plastic bag before tossing in the garbage bin.
Wash Down Sealed or Painted Wood
If the mold has grown on painted wood like an interior door or a sealed wood finish like floors, begin by washing down with a liquid dishwashing detergent and water solution. Mix one tablespoon of detergent to one quart of water. Use a soft-bristled brush to scrub down the surface. Try not to saturate the wood, use a sponge to remove excess water as you clean.
Spritz With Distilled White Vinegar
For a small amount of mold growth that has not left severe stains or penetrated the wood, distilled white vinegar can kill the spores. Use a spray bottle to lightly mist the wood with the vinegar. Allow the vinegar to remain and air-dry on the surface for at least one hour. If there are no stains remaining, buff the surface with a soft cloth.
Use Chlorine Bleach for Tough Mold Stains
If the mold is extremely heavy and has left stains after using vinegar, it's time for a stronger solution. This should also be used on areas of unsealed wood such as outdoor decks. Mix a solution of one tablespoon dishwashing detergent, 1/2 cup chlorine bleach, and one cup warm water. Apply the mixture to the stained area with a soft-bristled brush and allow to air-dry. Finish by buffing with a soft cloth.
What to Do If Mold Persists
If the mold stains still remain, the wood surface will need to be sanded to remove the spores that have deeply penetrated the wood. If you are not familiar with wood sanding or refinishing, ask questions at a home improvement store about the right sandpaper grit to use for your situation.
After sanding and vacuuming away all of the grit, the wood should be refinished or sealed to help prevent future damage.
How to Prevent and Remove Mildew - Home Methods. University of Missouri Extension