How to Clean Mold From a Wood Floor





Introduction: How to Clean Mold From a Wood Floor

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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    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!

    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.

    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.

    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.

    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.

    I've had my fair share of battles with mold. These are great DIY tips!

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

    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.

    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! ;)

    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!