Mold on wood. That’s a VERY broad and loaded topic. After all, you could be referring to mold on wood cabinets, mold on wood floors, mold on wood studs, mold on wood furniture, or even mold on wood décor.
Even more complex is what to do about mold on wood. You might be wondering what kills mold on wood. You may be looking for information on how to remove mold from wood. Or maybe you just need to know the signs of mold on wood or whether or not what you are seeing is indeed mold growth.
This article will look at the many aspects of moldy wood. Please feel free to jump to sections that answer your specific question by using the table of contents below. Because of the broad nature of this topic, I will be covering a lot of information.
Table Of Contents
- Why Does Mold Grow On Wood?
- What Types Of Mold Grow On Wood?
- What Are The Signs Of Mold On Wood?
- What Are The Signs Of Mold Under Hardwood Floors?
- Is Wood Mold Dangerous?
- How To Test For Moisture In Wood
- How To Test For Mold On Wood
- What Kills Mold On Wood?
- How Do You Remove Mold On Wood?
- How To Remove Mold On Wood Cabinets
- How To Remove Mold On The Wood Under Your Sink
- How To Remove Mold On Wood Studs
- How To Remove Mold From Wood Floors
- How To Remove Mold On Wood Furniture
- How Do You Prevent Mold On Wood?
Why Does Mold Grow On Wood?
Wood is an organic material that easily retains moisture. Wood also contains a variety of other materials, including sugars, starches, proteins, lipids and fatty acids. These materials are present in the storage tissues of the living tree and are essential for a variety of functions. Even after a tree is harvested, these materials remain in the wood and can provide the initial food source for mold.
Mold is rarely present inside a living tree because the bark provides an excellent barrier against fungal and insect attacks. Once the tree is harvested, these protective effects decline, and the many spores present in the air can settle on the surface and colonize the wood. Also, the food sources for mold, the stored sugars, starches and other compounds, are exposed when logs are processed into lumber.
Surface moisture on unseasoned lumber, appearing as the wood dries, may then create conditions for mold growth. Even though lumber is typically dried and treated with fungicides at the mill to prevent mold growth, moisture and mold spores do frequently get locked in lying dormant until conditions are right for growth. This lumber is then used to frame homes and other buildings as well as to make wood products (like cabinets).
That all makes sense, right? But how does that translate to mold growth on wood cabinets, wood floors, wood furniture, and other wooden household items? Isn’t the wood used to make these things treated with fungicides and sealed to prevent moisture intrusion and mold growth?
Yes. All wood building materials, wood used to make furniture, etc… should be properly dried, treated, and sealed. But as you saw above, this alone does not prevent mold growth. Mold spores are able to get past sealants, stains, varnishes, and paint. Give them some moisture in the form of high indoor humidity or a leak / water intrusion and mold will begin to grow on the wood in no time.
Beyond that, mold spores travel in dust. That spore can then land on your wooden cabinet (as an example) and begin to grow even without a lot of moisture. You touch your cabinets daily and transfer body oils, lotions, etc… Your kitchen cabinets get exposed to cooking oils. Bathroom cabinets get exposed to body care products, toothpaste, etc… You would be surprised what your cabinets are coated in. These debris provide a food source for mold spores and again, given the right conditions, mold can begin to grow on these wood surfaces.
Mold can also grow on wood because of human error. Walking around on a wood floor with wet feet introduces moisture. Not cleaning up spills, leaving wet towels on a wood floor, and putting dishes away in wood cabinets damp or with water droplets are all ways to jump start mold growth!
What Types Of Mold Grow On Wood?
A study at Oregon State University revealed that Douglas fir sapwood was colonized by over 45 types of mold within six weeks after sawing. Most of these species are common to many other materials, while a few were specialized and only grow on wood.
In short, there are many types of mold that grow on wood. Any mold growth on wood should be removed properly.
What Are The Signs Of Mold On Wood?
It can be very difficult to determine whether you have mold growth on wood just by looking it. Aging wood can become discolored and take on a mold-like appearance. However, there are a few telltale signs of possible mold growth on wood that you should be aware of.
- Water stains. If you have water stains this means that moisture was introduced into the wood at some point. Since mold flourishes in the presence of water, a water stain is a sign of mold growth on wood.
- Pigmentation (color spots) on the wood. Some molds produce pigmented compounds that stain the surface on which the mold is growing. Irregular patterned, colored stains may be an indication of mold growth.
- Visible texture difference. As mold grows, it will appear in a cluster which will produce a raised texture (which may or may not have color) on the wood. It may look fuzzy, smooth, shiny, puffy, or anything in between. If it doesn’t look like the wood around it, that is a strong sign you have mold on the wood.
- The wood is soft or crumbling. While other things like termites can also cause wood to crumble, mold growth very often will deteriorate wood.
- Odd odor coming from the wood. Mold can smell like anything or have no odor at all. This is by no means a hard and firm way to determine if you have mold on wood. However, over 50% of the time there will be an off odor coming from the wood.
What Are The Signs Of Mold Under Hardwood Floors?
- Cupping – when there is elevated moisture, individual boards will start to push out around the edges and be higher than the center. This creates an indentation that runs the length of the board that gives it a “wavy” appearance.
- Crowning – if there is more moisture in the center of the hardwood floor than the edge, the center may rise.
- Warping/Buckling – when a concrete subfloor has excess moisture in it, the evaporating water can be absorbed by the wood floor above it. This can cause the wood to pull away from the subfloor and separate.
- Discoloration that appears from the bottom up. This is usually due to moisture in the subfloor.
- Surface discoloration that appears splotchy. Floorboards may suddenly appear to be mismatched.
- Spongy feel when you walk on the floor.
- Water condensation on the floor itself without a water source.
Is Wood Mold Dangerous?
All mold has the potential to be dangerous. In the case of wood mold, not only can it cause health issues for the occupants of the building but it can also reduce the structural integrity of the wood it is growing on. Wood mold can be particularly dangerous since it is so difficult to see and may go undetected for very long periods of time.
How To Test For Moisture In Wood
Moisture doesn’t also mean mold but it is a pretty good indicator that you might have a problem. This is why you always want to check for elevated moisture levels in wood products and building materials.
Depending on what wood you are testing, there are a couple of different types of moisture meters you can use. You can check out my article on the best moisture meters here (which includes information on how to properly use them). Below are my top picks for specific moisture meters for various wood products.
Best moisture meter for hardwood floors
The General Tools MMD950 Moisture Meter is a pin and pinless deep sensing moisture meter which gives you the option of using pins in direct contact with a surface or using a spherical pinless sensor for a more versatile means of measuring. The meter specializes in detecting moisture content in subfloors and underneath wood flooring.
Best moisture meter for wood studs
The Protimeter Surveymaster is a dual-function moisture meter that offers homeowners a quick, easy, and one-handed way to measure moisture in wood studs. The Protimeter Surveymaster has two modes of operation: Search (non-invasive) and Measure (pin-type). These functions allow the homeowner to distinguish sub-surface and surface moisture, which is essential when investigating the extent of a moisture problem.
Best moisture meter for wood cabinetry
The Sam-Pro Tools Dual Moisture Meter measures the moisture content of just about any kind of wood, fiber boards, and particle boards. That makes it one of the most versatile moisture meters on the market, and one that’s great if you’re constantly testing different kinds of building materials. This is my top pick for any kind of cabinetry.
Best moisture meter for wood furniture
I would go with the Sam-Pro Tools Dual Moisture Meter linked above for wood furniture. It has done a great job on any kind of wood I tested.
How To Test For Mold On Wood
There are two different ways to go about testing for mold on wood cabinetry and wood furniture. Let’s take a look at the best tests for various scenarios.
Tape Lift Sampling
Tape lift sampling is very straight forward and the preferred method for testing for mold on cabinetry and wood furniture. You place the tape against the object (ideally in the area you see or suspect mold growth), seal it, then send it off for analysis. Mold Inspection Network DIY Mold Test Kit is my go-to for accurate tape lift sampling results. This kit includes three tests so you can sample from more than one location which is recommended.
Swab sampling works well but there is an extra step of transferring the material you picked up on the swab to the test plates. So there is some room for error that you don’t get with the tape lift test. In short, you use a sterile swab and rub it across the item you would like to test. You then swipe the test plate with the swab, seal it up, and send it in. The tests plates are cultured and analyzed. Immunolytics Diagnostic Mold Test Kit is my go-to for DIY swab sampling.
If you don’t care about the types of mold found, you can use these DIY test plates and culture them at home. This will show IF there is any mold growth but not what types of mold.
Testing hardwood floors for mold is a little tricky. Unlike wood cabinetry and wood furniture, the mold might be growing on the underside of the floorboards. A swab sample on the surface of the wood likely won’t produce a conclusive result.
For hardwood floors, you need to very carefully take a swab sample from the underside of a floorboard or two. You would do this by very gently prying up the floorboard JUST A LITTLE. Stick the swab under the floorboards and swipe it around as much as possible. Continue with the steps above and then immediately HEPA vacuum the area. Ideally you will be running a HEPA air purifier right next to the area you are working in.
Testing for mold on wood studs is not a DIY task. You will need to hire a professional mold inspector who can take core samples and send them to a lab to be analyzed. The other exception to this would be if the wood studs were already exposed and not sealed behind drywall. Then you can you the swab sample method mentioned above.
Be sure to check out my How To Test For Mold page. There is a lot of additional information available there.
What Kills Mold On Wood?
There is a lot of misinformation about what kills mold on wood. First, it is always better to REMOVE the mold from the wood as opposed to try to kill it. This is because you can’t really “kill” mold. You can render it inactive and it can go dormant but leaving this dormant mold in place is asking for problems down the road. So spraying a mold removal product on moldy wood and calling it good is going to backfire.
If you are looking for a product that you can use as part of your mold removal strategy, I suggest:
Click the links to learn more about each products, how it works, and how effective it is.
You can also visit my extensive article on Mold Removal Sprays for more information about additional products.
One VERY important note! Please do not use bleach to kill mold on anything! It only makes the situation worse.
How Do You Remove Mold On Wood?
I very rarely suggest a DIY approach to mold removal. Instead, I recommend you consult with a mold remediation company. One wrong move and you can contaminate your entire home.
If you do have a VERY small area of mold and wish to try the DIY approach, please be sure you have the following personal protective equipment:
- Protective clothing like a Tyvek suit
- Shoe booties (if not built into protective clothing)
Before doing ANY mold removal or cleaning, you will need to properly contain the area. Please see my post on how to properly contain an area you are remediating before proceeding.
How To Remove Mold On Wood Cabinets
If the mold is truly surface mold, then you might be successful at removing most of it with the proper products and a little elbow grease. The sneaky thing about mold is that it roots quickly and deeply and may have already penetrated all the layers of your cabinet. You won’t know if that is the case until you remove the surface mold and see if you get any regrowth.
- Once you have your containment area in place, begin by HEPA vacuuming the cabinets inside and out.
- Spray the cabinets with Superstratum Mold and Mildew Stain Remover. Allow to penetrate the cabinet for 10-15 minutes.
- Scrub the cabinet surface with a brush like this. Don’t be afraid to use some pressure. You want to make sure you get all of the spores.
- Wipe with cabinet surfaces with a damp cloth. Allow to dry.
- Spray the cabinets with CitriSafe or EC3 Mold Solution. This will render any rogue spores inactive. Allow to dry.
- Spray the cabinets with Superstratum Mold and Mildew Protectant to prevent any future mold growth.
If you believe that the mold on your cabinets has penetrated more deeply, the best thing you can do is to follow the steps above but instead of scrubbing the cabinet with a brush, sand the surface layer away. This of course means that as your final step, you would need to refinish or repaint the cabinets.
How To Remove Mold On The Wood Under Your Sink (aka the sink base or cabinet floor)
You don’t. You rip that board out and replace it. I replaced all of my wood under the sink areas with metal. It only makes sense right? If you decide to replace the wood with wood, be sure to get one of these awesome leak mats! They can save you a lot of time and trouble.
How To Remove Mold On Wood Studs
If you have mold on wood studs, it is best to replace these. There is no surefire way to remove all the mold since it likely has penetrated the wood stud all the way through.
How To Remove Mold From Wood Floors
- Pry away baseboard wall trim in the affected area.
- Pull up any transitional floor trim that is in the room.
- Carefully begin the process of ripping up the floorboards in the room. Begin at a corner of the room. If you think the mold growth is only in a small part of the floor and you want to patch only that area of the floor, remove only the trim needed to have access to the area of the floor involved plus two feet extra. You might observe further evidence of the presence of mold, so, be prepared to remove more.
- While I recommend replacing affected floorboards, I also understand that many people want to save their flooring. Since you will need to treat the flooring you removed, bag it up and place it outside.
- Treat the subfloor. Spray Superstratum Mold and Mildew Stain Remover all over the subfloor. Let it sit for 30 minutes. Scrub the subfloor with a brush before applying fresh solution again and waiting for another 15 minutes. Scrub the floor again. Allow to dry for 4 hours.
- After 4 hours, vacuum over the subfloor with a HEPA vacuum cleaner. This will remove most of the inactive mold spores.
- Treat the hardwood floorboards removed in the same way described above.
- After the subfloor and hardwood floorboards have dried, spray them with Superstratum Mold and Mildew Protectant. This is an amazing product (read my full review here) that will prevent mold growth for up to 25 years!
- Allow the subfloor and floorboards to try for a minimum of 24 hours before reinstalling the floor.
If the moisture and mold have rotted the subfloor or penetrated deeply enough to the extent of resisting removal, you will need to replace the subfloor.
- Saturate the material to weigh down the mold spores and then cut through the flooring using a reciprocating saw.
- Bag and remove the affected part of the flooring.
- Fix new subflooring, cut to fit, with screws every 8 to 10 inches length along the floor joists.
How To Remove Mold On Wood Furniture
Take the furniture outside as opposed to erecting a containment area.
- Begin by HEPA vacuuming the furniture inside and out.
- Spray the piece furniture with Superstratum Mold and Mildew Stain Remover. Allow to penetrate the for 10-15 minutes.
- Using a sander, sand the top layer of the furniture.
- Spray with CitriSafe or EC3 Mold Solution. This will render any rogue spores inactive. Allow to dry.
- Spray the piece of furniture with Superstratum Mold and Mildew Protectant to prevent any future mold growth.
- Re-stain, paint or seal with piece of furniture with a mold resistant product.
After ANY Wood Mold Removal Project, You Must Do This!
To ensure that you do not have mold spores in other areas of your home, you must fog with either Haven Mist or EC3 Mold Solution after your DIY mold removal project is completed and your containment area has been removed. Please see my article on Mold Foggers for more information on how to properly fog your house.
How Do You Prevent Mold On Wood?
- Keep humidity levels low. Make sure you monitor humidity with a humidity meter.
- Wipe up spills immediately.
- If you have a leak, flood, or larger scale water intrusion, dry out the area immediately. You do not want to wait more than 24 hours.
- To prevent mold on wood flooring, make sure your subfloor/foundation does not have cracks. Take the proper steps to prevent mold in your basement or crawlspace so it does not spread into your wood floor.
- Don’t leave wet items (like towels) on wood floors or wood furniture.
- Do not store unused wood furniture or décor in damp environments or areas prone to moisture like an outdoor shed or basement.
- Make sure that all wood is properly sealed or painted with mold resistant products (no unfinished wood). If the seal begins to wear off, reseal it as soon as possible.
- You can pretreat wood materials with Superstratum. This product can also be safely sprayed on wood furniture. You can read more about Superstratum here.
Sources for this article include:
- Kang SM, and Morrell JJ. 2000. Fungal colonization of Douglas-fir sapwood lumber. Mycologia92(4):609-615
- Zabel RA, and Morrell JJ. 1992. Wood microbiology: decay and its prevention. Academic Press, San Diego, CA. 474 pages.
- Western Wood Products Association