Removing mold/mildew from lumber

[Tom Giles]

I have some red oak that has, what I guess is, black mold and some with white mildew. What is the best way to remove this?

I could -

a. Plane it off but the boards are only 1/8 to 1/4 thicker than what I need
b. Chemically treat, bleach mixture or other cleaner
c. Pressure wash
d. Belt sander
e. Start a bonfire

What say the brain trust?

[Ralph Okonieski]

Do not use oxyclean! The oak will turn black.

[Paul F Franklin]

I wouldn't sand or plane, you'll end up releasing mold spores into the air. A mixture of real TSP (If you can get it in your area) and chlorine bleach or a mixture of borax and bleach should kill any mold. The bleach will alter the color of the wood somewhat, so test in a small area first. You could try just TSP or just Borax (skipping the bleach); it should remove the stains but is not as effective at killing mold as bleach.

[Bruce Wrenn]

Have you considered using Ozone to kill your mold? Amazon sells ozone generators for less than $100. We bought one this week to get rid of a "FUNKY ODER" that we had in a furnace closet (heat pump, not gas.) So far, it seems it worked. Also did my van, which has carpet that got wet. Worked there too. FYI, read the precautions about using an ozone generator.

[William Hodge]

I have some red oak that has, what I guess is, black mold and some with white mildew. What is the best way to remove this?

I could -

a. Plane it off but the boards are only 1/8 to 1/4 thicker than what I need
b. Chemically treat, bleach mixture or other cleaner
c. Pressure wash
d. Belt sander
e. Start a bonfire

What say the brain trust?

I have been working on a house that has a mold problem for a few years. New foundation drains, air sealing the gaps in the building envelope, and removing all the moldy heirlooms (including a braided rug that sat in an attic since 1978) helped. Getting the mold levels lower in the attic wood was easier when the warm, moist, house air wasn't feeding water and heat into the attic all winter. What to do with all the moldy heirlooms has caused some discussion.

The first thing I would suggest is that you get the moldy wood out of your shop. Bringing moldy stuff into a building adds spores, and mold will grow.

Anything that spreads the mold around, like cutting the wood, sanding it, or machining it will produce clouds of mold spores that will contaminate your work space and tools.

I have had success killing mold on raw wood with ozone treatment (watch your, and your pet's, lungs) and chlorine, followed by sealing with shellac. I built a tarp tent to ozone larger objects, like a gas furnace.

Lumber with white fungus and black mold has been contaminated into the grain, like spalted wood. Bringing moldy wood into a living space can spread mold into previously clean areas. I just filled a 10 yard dumpster with moldy and rotten wood.

Using the Google function on my computer system, I got a lot of ads and conflicting information, You must have seen the same.

[Frank Pratt]

HD et al sell mold remediation liquids that safer and work better than bleach or ozone.

[William Hodge]

HD et al sell mold remediation liquids that safer and work better than bleach or ozone.


Do you mean Concrobium?

It's a mix of sodium carbonate, sodium bicarbonate, sodium triphosphate, and water. It sounds like it's worth a try on the rough lumber garage walls I need to clean.

I have sodium triphosphate left over from cleaning noxious candle scent off the walls, floors, and ceilings. Baking soda is cheap, but sodium carbonate is even cheaper. Thanks for the tip. Spraying bleach on the attic ceiling was no picnic.

https://www.amazon.com/pounds-Sodium-Carbonate-increasse-99-95/dp/B01G6DXD2G/ref=sr_1_20?keywords=sodium+carbonate&qid=1636739428&sr=8-20

[Tom Giles]

I did what Paul suggested above - I used a mixture of TSP and chlorine. I sprayed it on and scrubbed it with a wire brush. It whipped the white mildew pretty easily. The black mold took 15 minutes or so for most to disappear. Only 2 out of 20 boards showed some grey where the mold was. I’ll let the lumber dry well then recheck and retreat as necessary.