How to Clean Mold From a Wood Floor




Introduction: How to Clean Mold From a Wood Floor

About: Eric J. Wilhelm is the founder of Instructables. He has a Ph.D. from MIT in Mechanical Engineering. Eric believes in making technology accessible through understanding, and strives to inspire others to learn …

This is how I cleaned up and removed mildew that grew on a wood floor.

I left a mattress directly on a hardwood floor, and some mold grew underneath.  There is no insulation in the crawlspace beneath the floor, so the temperature differential between warm bodies sleeping on the mattress and cold air under the floor resulted in condensation between the mattress and the floor, which is a perfect place for mold to grow. 

Mildew can also grow under potted plants and carpet, against uninsulated walls, in damp basements, if you have a water leak, or even under wet laundry left sitting too long. 

Step 1: Try Wiping Up the Mold

If the hardwood floor is properly sealed, you can just wipe up the mildew with vinegar, soap and water, dilute bleach, or some other common cleaning solution.  In our case, most of the mold cleaned up easily, but some had gotten into the grain of the wood.  The grain tends to suck up anything liquid, including the polyurethane used to finish our wood floors, which left those areas imperfectly sealed and able to absorb moisture.  In these areas, the mold was able to grow a few millimeters into the wood, making it impossible to wipe away.

The mildew growing on the intact polyurethaned surfaces wiped up so quickly that I didn't get a picture of it before we cleaned it up.

Step 2: Sand the Floor

Using 100 grit followed by 220 grit, I sanded all the areas with mold.  Since I didn't want to aerosolize a bunch of live mildew spores, I periodically sprayed a dilute solution of bleach on the areas I was sanding.

In the images, you can see that I tried removing the mold with steel wool.  That was unsuccessful, so I sanded.  If you use steel wool, be sure to clean all steel fibers up as any left may rust.

Step 3: Remove Dust

Since the polyurethane should be applied when the wood is dry, I removed the sawdust by dry wiping with microfiber followed by vacuuming.  

Step 4: Refinish Hardwood Floor

This was in an occupied bedroom and I wanted it to dry quickly between coats, and so I chose water-based low-odor polyurethane to refinish the sanded areas.  I applied a coat by brush in the morning, and the VOCs and solvent smell were long gone by bedtime.  I repeated this for several days, sanding lightly between coats as directed by the poly's instructions.

If you use a cheap hog-bristle brush as I am in the images, be sure to remove any loose hairs before you start applying poly so those hairs don't come out and get stuck in the poly.

The floor was originally finished with an oil-based polyurethane, so I didn't expect the refinished areas to match exactly.  However, they're normally out of sight (why mold grew there in the first place), and my objective was to seal-out further moisture rather than perfect them cosmetically. If this is a more visible area, test your polyurethane and consider applying a light stain.  If the appearance really matters, you should probably refinish the entire floor.

I made sure mold wouldn't be a problem again in the future by building a low-profile bed frame.

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    Mr. Potato Head

    Better plan - clean the freakin' house once in awhile! I mean how gross would a house have to get before it started growing mold on the oak floor. Uuugghh - give me the willies!


    Reply 6 years ago

    Great idea, unless someone spills a liquid under an antique metal Coke cooler sitting on an oak floor and it goes undetected for a short period of time.


    Reply 11 years ago on Introduction

    Mold indicate a moisture problem and it has nothing to do with the cleanliness of a home. Mold loves anything organic like gypsum board, wood, cardboard, paper, etc.


    6 years ago

    Thank you for writing an amazing article to prevent growth of mold. There are several ways to clean mold as i was reading an article where i found lot of possible solution which is not so much expensive and also clean the mold completely.


    7 years ago on Introduction

    Wood floors are
    beautiful and practical. But, if you allow water to stand on the surface, the
    finish will stain and mold may grow. This is especially true with water-based
    finishes, and in humid climates. Thank you for the great cleaning
    suggestions! I love Instructables!


    Swiss Cottage Carpet Cleaners Ltd.


    8 years ago on Introduction

    thanks for this info and for the replies...i'm going to try to the bio route


    8 years ago on Introduction

    I am glad to see the post from MaxCrunch. Most of the mold-removal products out there are bleach-based. Unfortunately, I bought and used a bunch of them before finding out the hard way that bleach actually makes things worse, just as he explains. In my case, this result was, I had to remove and dispose of 400 square feet of flooring.

    If I had to do it again, I would do exactly what he says, with one small change: researchers on behalf of the Australian government tested and determined whether natural "essential oils" were really effective in controlling mold. While they found that tea tree oil was not very effective, three other oils were: Clove bud oil, Eugenol, and Thyme oil .

    "Antimicrobial activity of essential oils and pure oil compounds against soilborne pathogens of vegetables", C. A. McMaster & K. M. Plummer & I. J. Porter & E. C. Donald, April, 2013.


    8 years ago on Introduction

    Nice DIY tips, ewilhelm!
    In general, items that you have used are not expensive but, for the other side, are effective in killing mold from wooden floor. Thx for share those tips with us! ;)


    9 years ago on Introduction

    I am going through this now. I recently bought a house, pulled up the carpet and yuck there is black musty urine smelling mold on my bedroom floor. Now, this "situation" was obviously not in the budget. We pulled up part of the carpet during the showing of the house to see the floor. The side we pulled up looked very nice; not even a scratch! So, we paint the room..... which came out very good, we didn't have to worry about the floor either because we were painting on top of the disgusting carpet. Finally... Time to remove the carpet, I broke the hammer and everything (New to DIY). Next, we discovered MOLD!!!!! I thought the carpet smelled but I assumed the previous owner had a dog.... NO, it was MOLD. Next, we do some research and we found two very well reviewed mold stain removal products safe for hard wood floors; I'm thinking Yesssss!!! Well, we are still cleaning it, it takes a few days in my opinion. This is day two; you notice a difference but you obviously have to keep at it. So far it's turning the mold white (game over noise) we have to sand those areas now. Our parents asked why we don't just sand the whole floor.... Well.... We actually planned to put new floors on top of them with sound proofing pads and MOLD preventing material. We will sand the areas for now and polyurethane.

    Items used in this project were:
    1. Dial soap and water to remove dirt and debris (We mopped)
    2. Mold Control (carried at Home Depot for about $9) (Sprayed)
    3. Mold Armor (We think this is what worked actually got it from Home Depot for $2.00)
    4. Baking Soda
    5. Contractor bags
    6. Regular Vinegar
    7. RUST-OLEUM Transformations 1 Kit Wood Floor Transformations Wood and Laminate Renewal (When we are done)
    This project has cost us almost $150.00

    I will post pics (Sorry not real before pics) and exactly how we did it.... Stay Tuned!


    10 years ago on Introduction

    I am sharing here some important Steps to Remove Black sports from your floors:-

    1:- First, you need to rub all the black sport area with a steel wool pad. You can also use some mineral spirits solvent to the area, if the mark is too hard to remove. Allow the material to dry on the floor.

    2:- You can use bleach to clean mark if the mark continues. Smoothly rub the mark area with the clean cloth.

    3:- Wash the mark area of the Wooden Floors with a damp or clean cloth. Mop the area dry with another clean cloth.

    4:- In the last step, polish the wooden floor to make smooth. Now you are ready to apply a small amount of floor wax to just coat the affected area.


    12 years ago on Introduction

    Hi there,
    sorry you had problems with the mold issues. Yes the bed directly on the floor was the issue and had nothing to do with issues of non-cleaning!

    Now I do like your instructable, and am only adding some info to it here. Also the Bleach as a Mold Killer is what people generally think works but it does not, just google the words and see the results.

    First off, I own and operate an ECO friendly cleaning company, we
    Clean and Restore Windows and Floors.

    I will follow this with some recommendations from my research and what we recommend to customers as well. (always use a two or three stage respirator and goggles along with rubber gloves when dealing with Mold and Mildew) or call in a specialist (bla bla other lawyer speak here, this our opinion only etc. )

    1st, Bleach is non effective against Mold, that is a proven fact look it up the American Mold Institute and the EPA have done extensive testing and found this to be true. Look up results from the CMHC Canada Mortgage and Housing Corporation. A. Bleach just kills most of the surface Mold leaving the roots to grown into the places that the Mold and Bleach which has just created more tiny holes for the roots to grow in.
    B. There are very effective Mold killers that are Chemical Based and Some that are Bio Based. I will deal with the Bio Based ones.
    LifeTime Solutions in the USA has a very good Bio Based Mold Blaster, and have used it with excellent results as well!

    2nd the Australians have been experimenting with Tee Tree Oil now for over 40 yrs to kill off Mold and other nasties. I suggest using GSE (Grape Seed Extract) and Tee Tree oil mixed in Distilled Water. 1ltr (pint) add in 40 drops of Tee Tree and from 35-45 of GSE.
    Spray the area, wipe off in about 4 min, repeat and this time let the solution sit for about 15 min or so. Repeat let it sit for about 45-55 min or so.

    3rd. Sprinkle Borax and Baking soda mix (60% Borax-40% Baking Soda) and spritze with the Tee Tree GSE mix until it looks like icing sugar, cover with plastic so it does not dry out fast and remove it in about 4 hrs. or so, wipe clean.
    - This is good for ANY surfaces, I did a wall in a basement that had mold and mildew growing on it 4yrs ago, it has not grown back since.

    Dry with fans on the Wood floor for about 6-8 hrs, use moisture meter to test.

    Get a clear polyurethane, mix in some Ageing or Amberizing Solution,
    use up to 4oz per 1/2 Gallon to make a wash to add some colour back into your sanded areas, or worn in areas. Lightly apply using a brush or my fav a Foam brush.
    Note - you will need to do this twice, 2 layers is much better than 1 heavy layer.
    use some cloth to or no lint paper towel to rub the edges so it is blended in. (No hard lines ! )
    Now, lastly lightly apply a thin coat of clear polyurethane over the spots, or re-coat the entire floor area.
    We have done this and you can not find the original bare spots at all when we are done, and to re-coat the entire floor just makes good sense and will last for years to come.

    Note - this is tricky and you might want to get someone else, a Professional to do this. We can help you on that one as well.
    Basic Coatings, Bona and Schwartz Chemicals all have a no sand/sandfree process and coverings to enable you to do this.

    Varathane and Minwax offer this as well, but it is not as good a product, look at the Taber Tests results to see as well. There is another Canadian based company out of Quebec that is awesome but I can not remember the name right now, sorry.


    12 years ago on Step 1

    I've been reading up on killing mold. Bleach looks like it's ineffective in killing mold. Vinegar is enough to slow down the mold but it doesn't look like it will kill it completely. I recently heard that Clorox Pro Results Outdoor will kill mold to the roots. It's supposed to have a "biocide" in it other than clorine. I'm still testing the truth of that claim.