Prevent Mold On Vinyl Fence: How To Stop Mildew Growth

Vinyl fences are a hardwearing, low-maintenance alternative to traditional wooden fences. They are considerably more durable, are easier to clean, and have a much longer life span. So It’s frustrating to go to your garden and see what looks like mold growing over your once pristine fence, it’s unsightly and also has the potential to be dangerous to humans and animals.

But why has mold grown in the first place, which types grow, and most importantly, how can you remove it and prevent its growth from occurring again? In this article, we will be covering all these questions and more. So, for everything you need to know about mold growth on vinyl fences, keep reading.

mold on vinyl fence

Why does mold grow on vinyl fences?

Mold (a form of fungi) will grow anywhere its needs are met, and despite the organism being incredibly complex in nature, its needs are very basic and to some degree, are similar to our own.

All mold and mildew require are a source of nutrients, oxygen, moisture, and an appropriate environment (such as a lack of direct sunlight).

Let’s take a deeper dive into how your garden may be the perfect environment for fungal growth on your fence.


The amount of moisture fungi need is relatively low, and humidity levels greater than 55% are all that is required to sustain mold growth. In warmer climates, humidity levels greater than 55% can occur for much of the year, providing all the moisture mildew and mold could need.

Of course rain itself, sprinklers in drier months, and any other direct sources of water will heavily contribute to the moisture available, and as vinyl is non-porous, any moisture will remain on its surface until it evaporates. This allows it to stay available as a source of moisture for far longer than it would on a traditional wooden fence which would absorb some (if not most) of the liquid.


You may be wondering just what mold and mildew “eat” in order to sustain themselves, and what possible nutrition could a vinyl fence provide anyway? Well, it certainly is not feeding off the vinyl itself but is rather feeding off organic materials that have collected on its surface.

Much as fungi might not be something you necessarily want growing on your fence, they play an important part in nature, feeding off of dead organic matter and leaving behind nutrients that can be absorbed by plants.

This means any dust, particles of dried, dead leaves or even microscopic particles leftover from mowing your lawn that may have collected on the fence are all excellent sources of nutrition for mold and mildew.

Lack of sunlight

Sunlight can prevent mold growth by lowering moisture levels and killing fungal growth, it is for these reasons that it tends to prefer growing in darker, shadier areas of the garden.

As a result of being shaded from the sun, moisture levels are kept high, and the temperature remains at an acceptable level for it to grow, without drying it out or killed.

Which types of mold grow?

Without accurate testing, it can be very difficult to determine which strain (or strains) you may be dealing with. The good news is that (as we will discuss later), it is not particularly important to know either way, as soon as you spot mold growth, it needs to go.

There are however several strains that are very regularly spotted in just the type of environment that your garden can provide. These strains are:

  • Alternaria
  • Aspergillus
  • Cladosporium
  • Penicillium
  • Stachybotrys Chartarum

This list is certainly not exhaustive, but these are the most commonly seen strains growing in gardens and outdoors in general.

Are they dangerous?

Perhaps frustratingly, the answer to this question has to be yes and no. The reason for this is that it is not as simple as being able to say that one type of fungi is dangerous and another is perfectly fine.

Some strains of fungi have the ability to produce mycotoxins as a defense mechanism. As the name would imply, spores with mycotoxins in them are toxic to humans and animals. Several of the above-mentioned strains have the ability to produce these mycotoxins, including Penicillium, Aspergillus, and Stachybotrys chartarum (also known as black mold).

The problem arises when you try to compare a non-toxic strain to a toxic one, If you were to inhale large quantities of spores from either, there could be negative health consequences even in otherwise healthy individuals. Even the “safe” strains that may have a lesser impact on a healthy individual could present symptoms in those susceptible to them.

This is why it is not particularly important to determine which strain you are dealing with, as all mold growth should be dealt with swiftly when it is first spotted so that symptoms do not have a chance to present themselves.

Some of the most common symptoms of mold exposure are:

  • Runny nose
  • Itchy eyes
  • Skin irritation
  • Coughing
  • Breathlessness
  • Sneezing

What about black mold?

Out of all the strains listed, I’m sure that “black mold”, was the one that got your attention. This is due to it having a great deal more media coverage than other strains.

Whilst black mold (Stachybotrys Chartarum), is indeed capable of releasing toxic spores into the air, exposure to them has never conclusively been proven to be worse for your health than other strains of toxic mold, such as some strains of Penicillium.

Exposure to its spores is likely to cause the same symptoms described above, and reports of “toxic mold syndrome” causing symptoms such as headaches, fatigue, memory loss, or an inability to focus”, have never been proven.

Despite this, whether you have asthma or a suppressed immune system or not, you should still always wear protective gear before attempting to tackle mold removal yourself, as even healthy individuals can be affected by spores.

What does mold in a vinyl fence look like?

Depending on the strain (or strains) growing, fungal growth on a vinyl fence can come in many shapes, patterns, and colors. It’s possible that you could have several growing on the fence at the same time, so different colors and textures would be expected.

Here is a quick breakdown of each type with its color and texture outlined.

Alternaria – Presents in small patches of powdery dot-like growth with dark or even black coloration.

Aspergillus – Another dark strain, coming in black or brown coloration, but with a white or yellow underside, and is again, powdery in texture.

Cladosporium – Displays in olive-brown, brown, black-brown, and gray colors with a powdery or velvet-like texture.

Penicillium – Usually one of the brighter colored molds, penicillium grows in blue, blue-green, gray-green, olive-gray, yellow, pink, or even brilliant turquoise, and again has a velvet-like to powdery texture.

Stachybotrys Chartarum – True “black mold” is unsurprisingly dark in color and can appear in growths of black, black-green, or very dark green. It sometimes grows in circular patterns and irregular shapes on other occasions, with a shiny or slimy texture, as it is a gelatinous mold.

Will mold damage a vinyl fence?

Fungal growth on a vinyl fence will damage it structurally over time, and when strains of mold and mildew consume nutrients on the surface of the fence, they release enzymes to break the materials down before absorbing them. These enzymes can damage the material, eventually causing cracking, chips, and fading.

These marks can sometimes be rectified with a mild detergent, whereas well-established mold may cause permanent staining.

Is it definitely mold?

One of the biggest factors when it comes to dealing with fungal growth on a vinyl fence, is to make sure what you are dealing with is mold in the first place.

What might at first glance look like fungi growth could in fact be a number of other substances, including algae, moss, or lichens. In order to treat the situation in the most effective manner, it’s important to establish which of these you are dealing with.

The following is a brief example of each to help you determine what may be growing.

Algae – Usually bright green when young, turning dark green to brown as it does back, and has a stringy and fibrous texture.

Lichens – Green to brown in their potential colors, lichens are a mix of fungi, algae, and sometimes bacteria, that appear with a crusty or leaf-like texture.

Moss – Grows most frequently in green colors, usually bright green with a soft and spikey texture.

Mold – Appears in many colors, with black, green, and gray being the most common. They often appear with powdery, velvet-like, or slimy textures.

Mildew – Often begins life with white coloration then can turn brown or gray and is also powdery or downy in texture.

How to test

A method to determine whether you are in fact dealing with mold or one of the other possibilities mentioned above is to complete a very simple test you can do yourself. Whilst it won’t confirm the strain you are dealing with, it will at least allow you to know how best to treat the problem.

Before you begin the test, you will need a few things.

  • Breathing mask
  • Rubber gloves
  • Eye protection
  • Cotton swab
  • Household bleach

As you will be getting close to what has the potential to be mold, you need to wear the protective gear listed above to avoid inhalation of its spores or coming into direct contact with it.

After putting on the safety equipment, dip a cotton swab in the bleach and gently rub it on the surface of whatever is growing. If it is fungal growth, after a few minutes its color will begin to lighten. Any other reaction, or no reaction at all means you are most likely dealing with one of the other potential causes listed.

Be careful not to get any of the bleach on the vinyl panel as this could cause staining. To mitigate this risk, find a patch of growth in an area that is less easily seen to conduct the test.

How to kill and remove mold from a vinyl fence

Before you attempt to remove fungal growth on your vinyl fence, it is important that you wear the correct protective equipment to ensure your safety. It is advisable to wear a breathing mask, and eye protection in the form of goggles and rubber gloves to prevent direct contact.

To kill and remove mold from a vinyl fence, use the following steps.

Step 1. Make a solution of one cup of distilled white vinegar to one gallon of water.

Step 2. Dip a sponge into the solution and apply it to the fence, ensuring there is plenty of the solution covering the patches of growth.

Step 3. Leave the solution to work for between 30 minutes to 1 hour. The acidity in the vinegar will break down the mold, killing it.

Step 4. After waiting for the mold to be killed, use a pressure washer, or a standard garden hose with a high-pressure setting to wash away the vinegar solution and any mold and dirt residue.

Step 5. If any mold or mildew remains on the fence, apply the solution once again, leave for 30 minutes, then use a clean microfibre cloth to remove any stubborn fungi. Wash down with the hose again after if necessary.

Can you use bleach to clean a vinyl fence?

No, much as bleach is often cited as being able to effectively kill mold, this is often not the case and may only lighten it, making it less easy to see. It is certainly not advisable to use it on a vinyl fence, as the powerful chemicals can damage the material, causing marks and shortening its lifespan considerably.

How to prevent mold growth on vinyl fences

Knowing how to kill and effectively remove fungal growth on your fence is useful, but prevention is always the best cure. So, in order to prevent mold from growing on a vinyl fence, (and to keep it from coming back), use the following tips.

Keep it clean

As stated, mold and fungi of any kind require nutrients in order to survive. As these can come from any organic source, preventing their accumulation is incredibly difficult if not impossible. However, keeping it clean by regularly hosing it down will remove the majority of organic matter available on the surface of the fence.

Use a high-pressure hose to clean the fence thoroughly at least once per month to make it a less hospitable environment for mold spores to create a colony.

Keep the moisture levels down

Once again, as your fence is located in your garden, keeping moisture away from it entirely will not be possible. There are steps that you can keep the moisture levels to a minimum though.

Ensure the reach of sprinklers is slightly short of the fence to prevent it from becoming saturated, and in high humidity areas, make use of hydrophobic (waterproof) paints to prevent rainwater or condensation from collecting on its surface.

Use mold prevention products

The above methods are highly efficient and environmentally friendly methods to prevent mold growth on vinyl fences, but if after trying them you still struggle with the growth, you can use mold prevention products.

Mold prevention products can be powerful and should be used carefully, so always make sure you carefully read the instructions and wear the correct protective equipment before starting treatment.

What can you spray on vinyl siding to prevent mold?

Products that you can spray over a vinyl fence to kill and prevent fungal growth can be a huge time saver and can be used effectively by most individuals.

It remains that these chemicals can be powerful, so the use of a breathing mask is especially important when using them. Use the products exactly as described on the can or in the manual and wear all protective equipment.


Mold on vinyl fences can ruin their appearance, making them look tired, unkempt, and generally worn out. Over time the fungi can not only leave marks and stains but can also damage the material, wearing it down and decreasing its lifespan. It is important to remove mold as soon as you have spotted it to prevent irreparable damage from being caused, and this can be achieved with a white vinegar solution and the use of a pressure hose.

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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