Mold on Wood: How to Remove It From Furniture and Studs

Mold feeds on organic material. NDSU Extension says mold grows on organic materials, such as paper, dirt, wood and soap scum. Wood alone isn't enough, though. Mold needs water, and the EPA says the key to mold control is moisture control.

Common moisture sources for wood:

• Roof and plumbing leaks
• Condensation on cold surfaces in humid weather
• Floods and storm water
• Humid storage spaces like garages, sheds and closets

In Texas, NOAA says the Gulf serves as the primary source of moisture, which is most readily available to the eastern part of the state. Furniture in a non-air-conditioned garage or shed along the Gulf Coast is a classic place to find mold on wood. The EPA recommends keeping indoor humidity below 60 percent (ideally between 30 and 50 percent).

Usually, yes. TDLR, the Texas agency that licenses mold professionals, says mold growth should be cleaned from non-porous surfaces such as concrete, metal, glass, tile, and solid wood. Compare that with drywall, carpet and insulation, which TDLR says should be removed and discarded when moldy.

The EPA's remediation tables, written for professionals, show the same thing. They describe four methods: wet vacuum, damp wipe, HEPA vacuum and discard (EPA remediation guide, chapter 3).

Table: EPA guidelines for wood surfaces with mold growth caused by clean water. Source: EPA Table 2.

Notice that discarding wood only appears for the large category. For small and medium areas, the EPA expects wood to be cleaned. Wood is different from drywall in another way too: the EPA's water-damage table says wet wallboard may need to be cut out, but for wet wood it says to remove moisture immediately and use dehumidifiers, gentle heat, and fans for drying, with a note to use caution when applying heat to hardwood floors.

These steps are for a small area, roughly under 10 square feet.

1. Fix the moisture source. The EPA says to fix plumbing leaks and other water problems as soon as possible.
2. Gear up. For small areas, the EPA's minimum is gloves, eye protection, and an N-95 respirator.
3. Work outdoors if you can. For movable items, Texas A&M AgriLife Extension says to clean mildewed items outdoors to avoid spreading spores indoors.
4. Vacuum loose growth. AgriLife suggests a HEPA vacuum, if available, to remove visible mold growth.
5. Scrub. The EPA says to scrub mold off hard surfaces with detergent and water, and dry completely. For finished wood, its water-damage table says it may be cleaned with mild detergent and clean water and allowed to dry.
6. Dry fast. The EPA's remediation guide says it is important to dry these surfaces quickly and thoroughly to discourage further mold growth.
7. Sand only if needed (see below), then HEPA vacuum the dust.
8. Don't paint or seal over remaining mold. The EPA says do not paint or caulk moldy surfaces and that paint applied over moldy surfaces is likely to peel.

About bleach. If you use it, the CDC's limit is no more than 1 cup of household laundry bleach in 1 gallon of water, and you should never mix bleach with ammonia or other cleaners. AgriLife notes bleach will not prevent new mold growth on materials that stay damp. Our vinegar vs bleach guide compares the options.

For solid wood furniture, University of Georgia Extension says to remove mold with a damp rag and solution of water and mild non-phosphate detergent. AgriLife suggests commercial furniture-cleaning products designed for the type of material, and says do not refinish or wax until thoroughly dry. For remaining mildew stains, it suggests wiping with diluted alcohol (1 cup rubbing or denatured alcohol to 1 cup water), then drying thoroughly.

Upholstered pieces are harder. The EPA's table lists upholstered furniture separately from wood and notes it may be difficult to completely dry within 48 hours. For antiques or heirlooms, the EPA says if the item is expensive or of sentimental value, you may wish to consult a specialist in furniture repair or restoration.

Studs, joists, rafters and subfloors are unfinished wood, so mold can work into the grain. NDSU Extension says scrubbing may not completely remove mold growth on structural wood, such as wall studs, so it may need to be removed by sanding. It adds: wear personal protective gear and isolate the work area from the rest of the home.

Sanding safely:

• Contain the dust. Sanding moldy wood sends particles into the air, which is why NDSU says to isolate the area.
• HEPA vacuum afterward. The EPA recommends HEPA vacuums for final cleanup of remediation areas after materials are dried and contaminated materials removed.
• Check for lead paint first. In older homes, AgriLife warns: do not sand or scrape lead-based paint.

After a flood, AgriLife says wall studs and plates may be sprayed with disinfectant (1 cup bleach/gallon water), then dried with dehumidifiers and fans. FEMA suggests using a Wet-Dry shop vacuum to clean studs or exposed wood framing. Before closing the wall, UGA says do not replace insulation and wallboard until wood framing moisture content is 15% or lower. A pin-type moisture meter checks this. See mold after a flood in Texas for the full flood cleanup.

What about borate products?

Borate (boron-based) wood treatments are often sold for framing. Research from the USDA Forest Products Laboratory found that boric acid and disodium octaborate tetrahydrate, used alone, have negligible or no mold inhibitor activity, even though they work against insects and decay fungi. The same 2013 study found that combining borates with certain fatty acids appears to act synergistically to inhibit mold growth. In short, a borate spray alone isn't a substitute for cleaning the mold and keeping the wood dry.

The EPA tables don't give a simple "replace if" rule for studs, but they and other sources point to a few clear cases:

Table: When moldy wood framing should be replaced.

Staining alone isn't a reason to replace wood. Strength is. Fixr also describes a type of fungus, Serpula lacrymans, that causes dry rot in the wood it feeds on and, if untreated, can eat drywall, lumber, subflooring, and siding. If you can push a screwdriver into a stud or joist easily, get a contractor to look at it.

Black or dark green spots on wood are common, and they don't automatically mean a dangerous species. The CDC says you do not need to know the type of mold and CDC does not recommend mold testing as a routine step. The cleanup is the same: fix the water, clean or sand, dry, and replace only what's damaged.

The CDC says people with asthma or who are allergic to mold may have severe reactions, so they should let someone else do the cleanup. Health questions belong with a doctor, not a mold test; TDLR recommends that people consult a health care provider. See our black mold guide.

There's no standard national price for cleaning mold off wood alone, because it's usually part of a wall, attic or crawl space job. Useful benchmarks:

Table: Costs related to mold on wood framing, national estimates.

See our mold remediation cost guide and mold in attic guide for more.

• The moldy area is more than about 10 square feet. That's the EPA's line for a small area affected by mold.
• It's 25 contiguous square feet or more. TDLR says that in most instances areas of visible mold less than 25 contiguous square feet in area may be cleaned or removed by people who are not licensed. Owners of residential buildings with fewer than 10 dwelling units are exempt for their own property.
• Framing is soft or structural. Removal companies handle the mold; a contractor handles the carpentry.
• It's inside walls. Opening walls disturbs mold; see mold on walls.

Texas law says a license holder may not perform both mold assessment and mold remediation on the same project. If you want the damage mapped first, hire a mold testing company, then a separate mold removal company. Find licensed companies in Dallas, San Antonio, El Paso or anywhere in Texas, check any license with our license check, and see how we verify listings.