Mold On Baseboard

Finding mold on baseboards is a frustrating experience. It can make them look unkempt, it can cause unpleasant smells, can indicate serious external wall issues, and can be hazardous to the health of humans and animals.

So why has mold grown in the first place, what kinds grow, how can you get rid of it, and most importantly, how do you stop it from coming back for good? In this article, we will answer all these questions and more. So, for all you need to know about mold and mildew growth on baseboards, keep reading.

mold on baseboard

What causes mold on baseboards?

Mold will grow on any surface where its needs are met, and despite fungi being a complex organism, their needs are relatively basic and not too dissimilar to our own.

All mold and mildew require, is a source of moisture (humidity levels greater than 55% for example), nutrients, and a small amount of oxygen. As long as these elements are available, fungi will not only live but thrive.

Now that we know what the requirements for mold growth are, let’s take a deeper look into some of the common causes of it appearing on baseboards specifically.


Moisture is, without doubt, the number one cause of mold growth on surfaces, and there are plenty of ways that it can find all the moisture it needs on baseboards.

High humidity

Rooms with a humidity level greater than 55% are prone to fungal growth, as the moisture within the air is able to condense and pool on surfaces, which the fungi can then use as a source of hydration.

Properties in high-humidity states are particularly at risk, as it is not uncommon to see moisture levels greater than 55% for many months of the year.

Rising damp

Lack of a damp proof course (DPC) in older buildings or a failed one in newer builds can lead to something called rising damp. This is when moisture from either outside or below the building is absorbed by the brickwork and sucked up and travels up through the wall. Usually, the damp proof course will create a barrier that this moisture cannot penetrate, but if it fails, rising damp can occur.

Signs and symptoms of rising damp include:

  • Tide marks on walls
  • Salt deposits cause bubbling of paint
  • Mold and mildew formation on walls or baseboards
  • Discoloration of paint or wallpaper

It is important to note that some experts have discredited rising damp as being a genuine issue in some buildings, so it is best to have a qualified expert assess your property to ascertain whether this is occurring or if there are other moisture issues (such as cracks in external walls) that may be the cause of water ingress rather than rising damp.


Condensation is a major factor when it comes to excess humidity levels within a property and is especially prevalent in new-build properties.

As building regulations change, more and more homes are being built to become more energy efficient by improving insulation and reducing gaps within the building that allow cool air to enter. Whilst this certainly cuts down on energy costs, it no longer allows fresh air to enter the building which drives out stale moisture-laden air.

The result is that this high moisture air has nowhere to go and will begin to pool (condensate), on cooler surfaces within the property. As these are often walls, water can pool and drip down the surfaces, collecting at the baseboard below, leading to either rot or mold and mildew growth.


Fungi don’t require vast amounts of food in order to live and breed successfully. They get ample nutrition from the dust and grime that naturally collects within a property over time.

Dust is made primarily of shed skin cells from humans and animals. These cells provide the protein and minerals the fungi need, as well as additional nutrients coming from other organic matter within the dust, such as dead plant material.

What does mold on a baseboard look like?

During its initial development, spotting mold growth on a baseboard can be difficult, this is because many strains start their lives with a white coloration that can easily blend into light-colored boards.

Fortunately, over time, many strains develop and change their color, making them easier to spot. The most common symptoms of mold growth on the front side of a baseboard include black or green patches of growth that can either appear as clusters of smaller spots, or large groupings.

There is also a high likelihood that you will smell the growth before spotting it, as a strong musty scent (often described as being similar to old socks), can be smelt whenever growth begins.

What does mold behind a baseboard look like?

As you would expect, mold growing behind a baseboard is far harder to spot initially. In this instance, it may be the smell as described above that you notice first, with little to no visible signs on the exterior of the baseboard.

Some of the telltale signs and symptoms of mold growth behind a baseboard are the board itself pulling away from the wall as the high moisture content within them expands the material, staining, and tide marks on the front surface, and paint coming away from the wooden board.

It is often only once the baseboard is removed from the wall for inspection that the true extent of growth is finally noticed, and as it can often take weeks or months to see any obvious symptoms, the growth can be extensive.

What does mildew look like on baseboards?

Mildew is very similar to mold, in that it is another type of fungal growth, and its needs are almost identical to that of mold (which is why it is often seen growing under similar conditions). However, it does have a few distinctive traits that separate it from mold.

Mildew is often seen in lighter colors than mold and can be found in white, gray, or light brown hues. It is also more powdery in its texture and has its own, distinctively unpleasant odor when compared to mold’s more velvet-like textures and musty scents.

Its growth tends to appear in similar shapes to mold, this being small clusters of dot-like growths that link together to form larger colonies.

What kinds grow?

There are thousands of varieties (or strains) of mold, however, some of them are found more commonly within properties than others. The four most commonly seen strains include:

  • Aspergillus
  • Cladosporium
  • Penicillium
  • Stachybotrys Chartarum

This list is certainly not exhaustive, and there could be hundreds of variants that would happily set up home on your baseboard if the environment was correct for it. Without proper testing, it can be incredibly difficult to know which strain you are dealing with, and in all honesty, it doesn’t really matter which you have growing, as it needs removing either way, as it can be dangerous as we’ll explain later on in the article.

Some of these strains do have signature colors and textures that may help with identification, if you’d like to try to determine which is growing in your property, you can use the guide below to see if any match up to what you can see. Just be careful not to get too close, and if possible, wear goggles and a breathing mask whilst you inspect.

Cladosporium – Has dark brown coloration, sometimes containing flecks of dark green, with a powdery or velvet-like texture. It is often found growing in colonies or clusters.

Penicillium – Blue/gray in color, with sometimes green-blue, gray-green, or even yellow, pink, or brilliant turquoise, with a wooly or cotton-like texture. Grows in small clusters that join together to create larger patches of growth.

Aspergillus – Often mistaken for black mold, Aspergillus strains have dark coloration in either dark brown or even black in some variants. Presents with a suede-like texture and grows in large groups of irregular circle shapes.

Stachybotrys Chartarum – True black mold, Stachybotrys Chartarum is unsurprisingly dark in color, often appearing in very dark black or black-green coloration. Its texture can change depending on the moisture level from either shiny or slimy. This strain initially grows in small patches of closely positioned dot-like patterns, creating large patches of irregularly shaped colonies over time.

White mold

Many strains of fungi start out with white coloration that often changes over time. There are however several strains that are more likely to retain a white colour over a longer period of time. These strains include:

  • Aspergillus
  • Penicillium
  • Cladosporium

As we have discussed earlier in this article, these strains may appear in varying hues, and the changing of their color is often attributed to humidity levels, the nutrients they consume, and the amount of light it is exposed to.

Black mold

If you are looking at black mold growth on your baseboards, you are most likely looking at Stachybotrys Chartarum. This is true toxic black mold, however, there are additional strains that have very dark colorations that can appear almost black. Aspergillus niger for example is frequently mistaken for true black mold.

One way to determine whether the black mold you are seeing is Stachybotrys or Aspergillus niger is to look at its texture, as true black mold will be wet and slimy, Aspergillus niger is more powdery or velvet-like.

Brown mold

There are a good few varieties of mold that can grow within a property and therefore, also on a baseboard with brown coloration, some of them more toxic than others, including Pithomyces chartarum, Stemonitis, Cladosporium, and Mucor.

Out of these strains, Mucor is the most toxic and poses the greatest health threat, however, bear in mind that it can be extremely difficult to tell which strain you are looking at by texture and color alone. In order to be certain, testing should be carried out to get an expert diagnosis.

Are they dangerous?

In many cases, yes, mold of any type has the potential to be hazardous to humans and animals. This is because even the non-toxic strains can still be an allergen to people sensitive to them, so even if the strains do not create life-endangering symptoms, they can still negatively impact a person’s health.

Some strains of fungi have the ability to create mycotoxins as a defense mechanism, When inhaled, they can produce respiratory symptoms, and if ingested, the symptoms can become very dangerous, potentially even life-threatening.

Inhalation of toxic spores has never been confirmed to cause what has been referred to as “toxic mold syndrome”, with symptoms such as brain fog, cognitive difficulties, abdominal pain, weight gain or loss, or a metallic taste in the mouth.

Some of the more common (and likely) symptoms you could suffer from after mold exposure are:

  • Breathing difficulties
  • Coughing
  • Wheezing
  • Sneezing
  • Watery eyes
  • Skin irritation

These effects can be felt especially in people who have allergies related to mold, but if exposed to large quantities of spores, or over a long period of time, even otherwise healthy individuals can begin experiencing symptoms.

How to get rid of mold on a baseboard

If the worst has happened, and you’ve noticed mold growing on your baseboard, you need to remove it as quickly as possible. As you will be getting close to the fungi in order to remove it, you should wear protective equipment to keep yourself safe, even if you have no allergies.

If the amount of growth is superficial (only a few specs here and there), then you should have no major issues removing it yourself, but if the growth is considerable, you may need to hire a professional to not only remove the growth but to help you identify the source of the infestation.

It is recommended that you wear eye protection (goggles), a breathing mask, and rubber gloves. This will minimize the potential for contact with spores.

Once you have your protective gear on and have opened windows and doors to increase ventilation, you can begin killing and removing the mold by using the following steps.

Step 1. Vacuum the area to remove loose spores. Remove the boards to allow you to clean them thoroughly and to inspect if there is any further growth behind them.

Step 2. Create a solution of one cup of distilled white vinegar or rubbing alcohol to three cups of water.

Step 3. Dip a cloth into the vinegar/alcohol solution and dab it over the patch of growth, ensuring it is fully covered in the liquid.

Step 4. Leave the solution for between 20 minutes to an hour to kill the fungal growth.

Step 5. Using a clean cloth, wipe away the dead mold and any residue it leaves behind. For painted baseboards, the mold should come away easily, untreated wooden boards may need a mild detergent to help remove any stains the growth may have caused.

Step 6. Leave the boards to fully air-dry and then put them back into place.

What about mold behind baseboards?

One of the reasons we suggested removing the baseboard before cleaning it, is because it allows you to complete a quick inspection of the area behind it.

If no mold is found growing behind your baseboard, it is only a superficial issue that can most likely be rectified by cleaning and increasing ventilation through the property, however, finding it growing behind your baseboard can indicate a much larger problem, such as rising damp or leaks, as we have previously discussed.

In order to successfully remove mold behind baseboards, use the following steps.

Step 1. Find the source of moisture by using a moisture meter. Locate where the moisture is coming from and address the underlying issue. If it is coming from rising damp, an expert will be required to place damp proofing, if leaks are discovered, a plumber may also be required to rectify it.

Step 2. Remove the baseboards to give yourself plenty of access to the affected areas. Remove several strips to allow you to complete a full inspection and not miss any potentially affected parts of the wall.

Step 3. Create a solution of one part Vinegar to two parts water or rubbing alcohol. Dip a cloth into the solution and ensure the patches of growth are covered in the liquid. If possible, try not to saturate the area with the liquid or you could worsen the situation. If a large area is affected, you can put the solution in a spray bottle and apply it to the wall.

Step 4. Leave the solution to work for between 20-30 minutes, then use a mild detergent and a clean cloth to remove the dead mold and any debris behind the baseboard.

Step 5. Once all the mold is removed, allow the boards and wall to fully air dry. If the cause of growth was a leak for example, after cleaning the mold and fixing the leak, you should consider drying the room by using dehumidifiers, and fans and increasing your central heating temperatures for a few days before replacing the boards.

When to call a professional

Superficial mold growth on baseboards or any other part of a property can nearly always be dealt with at home without the need for professional assistance. If fungal growth returns again quickly after being treated or grows in several places within the property at the same time, it may well be worth hiring a professional to assess the situation.

Mold remediation professionals will have had plenty of experience in dealing with fungi and will know the most likely causes of their growth in properties like yours. They will be able to quickly identify and correct the issue, which can ultimately save a lot of time and hassle for you.

What is the best cleaner for mold on baseboards?

Home remedies such as vinegar and rubbing alcohol should kill most superficial fungal growth, but if these methods have failed, you can opt for a specific product designed to kill mold.

To make life a little easier, I have suggested a few products below that are particularly effective and come highly rated.

How to prevent it from growing again

Being able to kill and remove the growth is one thing, but being able to prevent its return or stop it from occurring in the first place is certainly preferable.

So, to prevent mold growth on baseboards, use the following tips.

Keep the moisture below 55%

Fungi only need a small amount of moisture in order to breed and survive, humidity levels within a room or property greater than 55% create an environment where moisture can condense on cooler walls and surfaces, creating droplets or pools.

These pools are ideal for mold to use as a source of hydration but can be remedied by keeping humidity levels low. Using a hygrometer to keep a check on the overall moisture within the air is an excellent first step in preventing mold growth.

Place a hygrometer in several rooms of your property to get an overall idea of moisture levels, and to help identify problem locations.

If high moisture levels are discovered, consider opening windows, and doors and increasing ventilation generally to allow fresh and dry air to replace stale moisture-laden air.

In particularly high humidity states, levels can reach greater than 55% many months of the year, so taking additional steps such as using dehumidifiers may be required.

Ensure your exterior walls are waterproofed

Checking for cracks and defects in brickwork will help to reduce the ingress of water, but even if none can be found, waterproofing exterior walls is an excellent additional layer of protection.

Using a silicate-based sealer will add a layer of waterproofing to exterior walls and reduce the likelihood of water seeping in and causing rot or mold growth to the interior of the brickwork that could seep through and affect your baseboards.

Sealants can be purchased and applied without the need for professional help.

Check drainage systems

Faulty drainage systems from toilets, showers, or guttering can cause large amounts of water to be deposited on the exterior of a property. If this water pools, it can be absorbed into the brickwork, causing damp issues.

Regularly check guttering for any damage and fix any leaking wastewater pipes to ensure they are functioning correctly and draining water away from the property.

Inspect your boards regularly

Due to their location, the state of a baseboard is something that can very easily go without inspection for many months or years.

If possible, check your baseboards every month to see if there are any signs of rot or mold growth. Spotting growth early on is certainly preferable to leaving it to develop over several months, as this will lead to more damage and a far bigger and more costly repair job.

Use your air conditioning to prevent fungal growth

Mold grows at its fastest rate between 60-80 degrees Fahrenheit, so using your air conditioning to keep temperatures below this level will help to prevent or at least slow its growth.

This point is especially true for properties in high-humidity climates as previously mentioned.

Dry the house after any water damage occurs

Water damage can come from flooding, broken pipes, and many other causes, it is very important that once the underlying issue has been resolved, the house is fully dried to prevent rotting or mold and mildew growth not just on baseboards, but through the whole property.

This may require turning the central heating on to a higher temperature (70 Fahrenheit and above) for several days, using dehumidifiers, fans for increased ventilation, and additional heaters if required.

Increase ventilation

Most new-build properties face the issue of a lack of ventilation. This is because they are designed and built to be air-tight to prevent loss of heat.

Whilst this is good for the environment and can save on energy costs, it creates an environment where stale, moisture-laden air cannot leave a property.

This moist air can condense on cooler surfaces, including baseboards. Pools of water collect on the surfaces which can be used by mold as a source of hydration, and so this needs to be prevented.

Opening windows and doors, and if required, making use of positive input ventilation (PIV) units is an efficient and highly effective way to increase ventilation in your property that drives out high moisture air and draws in dry, fresh air.

Passive ventilation vents can also be placed in several spots throughout a building to increase airflow to a similar effect.

Use anti-mold primer on your baseboards

Addressing the underlying cause of mold growth in your property should be a priority, but adding a coating of mold-proof primer will help to prevent growth in the areas it is applied to.

These primers create a slick surface that fungi find difficult to attach themselves to, preventing a colony from being able to form. It should be stated that these primers should be used in conjunction with solving humidity issues that are likely causing the growth.

Regularly clean the area around the boards

As air passes through a room, it picks up specs of dust and dirt. This is exactly what mold feeds off, and it often collects at the base of a room, especially in corners. A fine covering of dust on a baseboard will provide adequate nutrition for mold, so keeping the room as dust-free as possible will remove one of the elements it needs to survive.

Regularly vacuum rooms to keep dust levels down, paying special attention to the corners and sides near the baseboards where they can collect in larger amounts.

Fix any leaks quickly

Large leaks are often corrected very quickly to prevent damage to a property, but smaller leaks in pipes or brickwork can either go undetected or can sometimes be put off to a later date.

This is not recommended, as even small leaks can create large amounts of water ingress over time, and can be just as damaging to the internal structure of a property.

If you suspect any leaks or see any signs or symptoms of unexplained water damage, seek professional advice to locate its source and have it corrected.

Doing this will lower the overall humidity levels within a property, lessening the possibility of mold and mildew growth.


Mold on baseboards is not uncommon, as under the right circumstances, they can provide the perfect environment for its growth. Removing the mold is simple if only superficial, and can be achieved with white vinegar or rubbing alcohol, but be certain to check there is no mold behind your baseboards. You can prevent its growth by keeping humidity levels below 55%, and regularly cleaning and inspecting the boards.

Chris Walker

Chris Walker has struggled for several years with mold after buying his own property. After finding the solutions to several issues around his home, he decided to create this site in order to answer as many questions about mold and mildew as possible to help others dealing with the same problems.

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