How to Treat a Mold Infestation on Wood With Borax 20 Mule Team Powder

Updated on August 16, 2019
Maren Morgan M-T profile image

Maren is a one-person fixer of "TLC Needed" houses. She explains methods simply to homeowners who are not in the construction trades.

The underside of flooring coated with Borax "paint."
The underside of flooring coated with Borax "paint." | Source

How to Kill Mold With Borax "Paint"

Perhaps one can expect to find a little mold in any home, especially a home with a basement or which is located in a humid climate. However, there is such a thing as too much mold. When you are challenged with the latter situation and cannot afford outside mold remediation services, one of the DIY options is to kill the mold with the detergent booster Borax (TM).

Step One: Personal Protective Gear

Do not be casually confident that you are a healthy person and your immune system can defend itself. Be safe, not sorry. Buy a face mask and borrow or buy goggles.

The face mask recommended for mold removal is called a respirator, which sounds more ominous than it really is. The P100 or N95 mask is what is required. These are made by several companies and have varying features. I love the 3-M N95 with a nostril valve. It allows for better exhalation and stays dry. Once I bought a cheaper N95 which had no nostril valve. It complied with the NIOSH standards, but the moisture in my exhaled breath condensed on the inside of the mask and I was feeling a damp mess on my chin.

I normally wear glasses which have saved my eyes from injury many a time, as I do carpentry or gardening. However, my mold consultant strongly recommended eye goggles for anyone working above her own head. Naturally, painting a ceiling has one working overhead. So, I bought and used goggles which turned out to be very comfortable and not vision-obscuring.

My hair protection is merely an old ratty white T-shirt turned inside out as if I was pulling it off, but got stuck around my face. (Didn't you ever do this when you were a child?) I pulled the long ends in front of my neck and used a safety pin to attach them.

Completing the gear are an old long-sleeved shirt and long pants and plastic clogs (socks, too.) I launder them separately from any other clothing.

Personal Safety Is Paramount

For working above your head on mold cleaning, include a respirator, goggles and a covering for your hair.
For working above your head on mold cleaning, include a respirator, goggles and a covering for your hair. | Source

Step Two: Prepare the Area

Identify the moldy area and brush or sweep away loose debris. Bag this and dispose of it. Then vacuum the same area, preferably with a HEPA vacuum cleaner. If you need to set up work lights, do this now. Also, gather any ladders or step stools you will need for the painting job. If you can open windows or doors to provide yourself with fresh air and ventilation.

Flooring with black mold after it has been brushed and HEPA-vacuumed.
Flooring with black mold after it has been brushed and HEPA-vacuumed. | Source
Bring bright light to the work area.
Bring bright light to the work area. | Source

Step Three: Make Borax Paint

Finding Borax in stores may be a bit of a project for you. It is considered a laundry product, so go to the clothes washing aisle of your stores. I have found it at a big box store (thank you, Supreme Being!) but usually there is only one box on a bottom shelf. If you find a large supply, I recommend that you purchase a box for every 300 square feet which you plan to treat.

Why Borax? It is not toxic to you, the homeowner, and it is effective in kllling mold. All the safety equipment described above is for protection from the mold, not from the cleaning agent.

The recipe given is one cup of Borax dissolved in one gallon of water. HOWEVER - I found two problems with that. The first is that it is cumbersome for me to haul a 1-gallon container of Borax paint up a ladder to paint the underside of wooden sub-flooring. The more important reason for changing this, though, is because Borax is not the easiest material to dissolve. Or, to stay dissolved.

Therefore, I use 1/2 cup to 2 quarts of water - BOILING WATER, that is. I put the dry powdered Borax in a manageable sized 2+ quart saucepan (another advantage is the handle - ease of carrying around) and then pour in boiling water from a teakettle and stir. This at least starts the paint as fully dissolved. Some Borax will eventually settle to the bottom of the saucepan before I am done painting, but it is nothing compared to what sits at the bottom when I have used cold tap water. Since I work in either unheated or barely heated areas, the paint cools quickly and I am not in danger of burning my skin with scalding water.

Preparing Borax Mixture
Preparing Borax Mixture | Source
Preparing Borax Mixture
Preparing Borax Mixture | Source

Step Four: Paint Ceiling and Joists With Borax

Cover every bit you can reach with your "paint." It looks rather clear, more like cloudy water than an opaque white. When it dries, it will look much more white.


Good Luck To You

I hope this helps those beleaguered with weather- and disaster-related wetness. Please comment to let me know how it goes for you.

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

Questions & Answers

  • Can you paint over the borax concoction after it dries?

    Yes, you can. First paint a lime chemical whitewash, then paint your desired color. The lime seals in any mold hyphae (roots) and prevents it from regrowing.

  • Can I use borax for mold in a garage door?

    Yes, as long as you are not impeding moving parts.

  • I have a large area, about 1500 sf of subfloor I need to treat. Can I first spray a vinegar solution to help with the odor, then once it dries use the borax paint on this wooden subfloor?

    Yes. Make sure the vinegar dries before going to the next step.

  • Do you need to clean the mold off first and then paint the borax on or can you just paint the borax on and that then takes care of the mold? Will painting the borax on wood keep mold from growing again? This is in a crawlspace under a house on joists.

    First, you absolutely must clean off the mold safely with a HEPA vacuum cleaner. Next, do the Borax paint and THEN: to seal the roots so that it does not grow back, do the whitewash paint. Be safe.

  • I don't plan on painting after treatment with Borax (plywood roofing in attic). What would I follow up with to clean the mold off of the wood? My husband tried something from a big box store which he sprayed on and scrubbed. It did take some of the mold stain off, but I don't want to use anything so toxic.

    In the mold treatment I describe, mold hyphae (roots) remain in the wood. The whitewash painting step seals them in, so they cannot do any more growing and "spewing." If you don't want to paint the wood, you have done only part of the process.

© 2012 Maren Elizabeth Morgan


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    • Maren Morgan M-T profile imageAUTHOR

      Maren Elizabeth Morgan 

      13 days ago from Pennsylvania

      JennyBlythe, I used dolomitic lime because that is that I could find in the big box store near me. It worked very well.

      Good luck to you -- please consider getting and using a dehumidifier for the rest of your days to reduce the moisture/humidity that molds love.

    • profile image


      2 weeks ago

      Hello, does it matter if you use pure quicklime or dolomitic quicklime for last part if project?

    • Maren Morgan M-T profile imageAUTHOR

      Maren Elizabeth Morgan 

      8 months ago from Pennsylvania

      Jill, I am guessing that the cabinet is wooden. To be extra careful, I suggest that you do all the steps (vacuum, Borax, lime wash) to the entire cabinet - while wearing a face mask, of course. :-) Enjoy your project!

    • The Dirt Farmer profile image

      Jill Spencer 

      8 months ago from United States

      I'm really glad to have found your article, Maren. My project for next weekend is to chalk paint a cabinet with a little mold on the inside of one of the doors. I was wondering what to do about it. So I should paint with the Borax-water concoction and then give it a lime wash before painting?

    • Maren Morgan M-T profile imageAUTHOR

      Maren Elizabeth Morgan 

      12 months ago from Pennsylvania

      Someone asked if Borax would work against termites, especially in combination with other chemicals. Since I ahve no expertise in termites and also no idea what will happen mixing Borax with fizzing household products, I decline to give an opinion.

    • Maren Morgan M-T profile imageAUTHOR

      Maren Elizabeth Morgan 

      15 months ago from Pennsylvania

      Yes. You will allow it to totally dry and then paint your whitewash over it.

    • profile image

      dave p. 

      15 months ago

      Once it is paint on you just leave it there?

    • profile image

      Susan E. White 

      3 years ago

      I really appreciate you posting this for we poor people not just this mold cure, but also all the wonderful fantabulous tabs for home improvement & the like. Thanks a million. I used to work & probably could've almost afforded a professional, but now, I gotta do it myself. I was thinking about what you said about dissolving the Borax being a bit of a bear & I totally agree. Maybe you could use very hot tap water & put the Borax in the blender to break it down better, then add it to the full gallon (or 2 quarts) whatever works, but I hope you don't have to do this tiresome job again if you don't have to. I personally am going to put the solution in a larger garden pump-type sprayer, so I can really load up alot of Borax solution gallons & not have to change water alot. Mine has a shoulder strap which helps a little.

    • Maren Morgan M-T profile imageAUTHOR

      Maren Elizabeth Morgan 

      4 years ago from Pennsylvania

      Jon, great idea.

    • profile image


      4 years ago

      When I mix Borax with Murphy Oil Soap it dissolves very quickly. The ph of MOS is around 11 and Borax is above 9. It would be easier if I could take a bowl, brush, box of Borax and bottle of MOS down in the crawl space and mix as I go.

    • Maren Morgan M-T profile imageAUTHOR

      Maren Elizabeth Morgan 

      7 years ago from Pennsylvania

      AliciaC, you are most welcome. Since you are a scientist - it is nice to know that you find this information vaild.

    • AliciaC profile image

      Linda Crampton 

      7 years ago from British Columbia, Canada

      Thanks for the useful information about borax, Maren Morgan, and thank you for describing the safety precautions that should be taken when trying to remove mold. I appreciate the details about respirators, too.

    • profile image


      7 years ago

      Interesting information to have on hand in case of need. Thanks for easy-to-follow directions.


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