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Why Do Wooden Fences Turn Green? (And How to Prevent and Fix it)

Why Do Wooden Fences Turn Green? (And How to Prevent and Fix it)

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Having a fenced-in yard is important for many people. Some just want to be able to enjoy a bit of privacy while others need fences so that they can let their dogs outside safely.

If you have an old wooden fence, you might have noticed that it doesn’t look as good as it used to. Sometimes wooden fences will turn green, and many don’t know why this occurs.

Why would a wooden fence turn green after many years have passed? Is the fence moldy or is it green for some other reason?

Read on to find out why this happens, so you can stop it going forward.

It’s Related to Mold Issues

The reason why your wooden fence is green has to do with mold issues. Well, it’s possible that it could be mildew or green algae as well.

Whenever you notice a wooden structure start to turn green, it’s going to be because it was exposed to moisture. All fences are going to be exposed to moisture, but they have to be protected to keep mold, mildew, or green algae from causing problems.

A green fence is one that has retained water. This moisture has made it possible for mold to grow, and it’ll only get worse if you ignore the issue.

If you have an old wooden fence that has been green for quite some time, there’s a good chance that it’s incredibly moldy. It might not be as structurally sound as it should be either.

Fences will weaken when they are in this state. The wood is going to rot and it won’t be able to last forever.

Understanding Green Algae Issues

Green algae will be the least problematic issue that will cause fences to turn green. It’s a bit easier to deal with green algae than it is to handle mold or mildew issues.

It’s actually a harmless type of fungus, but that doesn’t mean that you want it to remain on your fence. Green algae forms on wooden fences due to the surface getting wet.

You’ll also find that it grows in the shade. This means that when it’s wet and overcast, it’s possible that green algae will become a problem for your wooden fences.

Thankfully, it doesn’t actually harm the integrity of the fence. It’s mostly going to be a cosmetic issue that you’ll want to take care of.

Understanding Mold Issues

Mold is not going to be as simple to handle as green algae. It’s another type of fungus, but it isn’t harmless.

If you leave mold on the fence for too long, it’s going to damage it. Mold grows on fences when they retain water and aren’t able to get rid of it.

When fences get exceptionally wet, it’s more likely that they will get moldy. If the sun hasn’t dried up the water, it’s going to sit on the fence, and this will cause the mold to grow.

Sadly, it’s not going to be easy to prevent mold from growing on wooden fences completely. Sometimes the weather will create a perfect situation where it can grow.

Ideally, you want to take steps to remove mold from your fences as fast as you can. If you wait too long, the fence could become irreparably damaged.

Understanding Mildew Issues

For the most part, mildew issues are very similar to mold issues. In some ways, you can consider this the middle option between mold and green algae.

It doesn’t cause as much damage to wooden fences as mold does. However, it’s not as harmless as green algae.

You don’t want to ignore mildew that is growing on a wooden fence. It can harm the fence, but it isn’t quite so hard to get rid of.

Doing your best to be proactive about mildew issues should allow you to take care of things just fine. Since mildew is pretty much the same as mold, it’ll be possible to use similar methods to remove it from the fence.

Power Wash the Fence

Power washing the fence is the most practical way to remove mold, green algae, or mildew. It’s certainly a good idea to own some type of power washer so that you can take care of your fences when necessary.

If you notice any green spots on your wooden fences, you should power wash them right away. It’s also acceptable to just preemptively power wash the fence a few times each year.

Many people choose to power wash their fences on regular schedules. You might choose to power wash yours once in the spring and then again in the fall.

It might make more sense to use the pressure washer on the fence when necessary, though. Thankfully, these handy pressure washers are fairly affordable.

Remember that you won’t be able to use this method if you’ve waited too long. If the fence has been significantly weakened by mold or mildew, the pressure washer could harm it.

Check to see if the wood is cracked or eroded in any way. If the fence isn’t in good shape, power washing probably won’t help as much as you’d like it to.

This is a great way to take care of your fence so long as you’re taking care of things before they get too bad. You can’t necessarily revitalize an old and worn-down fence using this tool.

Scrub the Fence Manually

So, what if you don’t own a power washer? Is there still a good way to clean the fence so that it won’t be green any longer?

If you’re willing to put in some effort, you could scrub the fence the old-fashioned way. Simply grab a scrub brush and start working on the fence.

It’ll be a good idea to get yourself a bucket of warm and soapy water. Using dish soap isn’t a good idea since it won’t be able to kill the mold.

Instead, you should mix up a bucket with some type of bleach solution. Since you’re going to be dipping the scrub brush in the bucket, it’s going to be best to wear gloves for this process.

It can take some time to clean mold, mildew, or green algae using this method. Some might not have the patience for this, but it is a reliable way to clean the fence that will work just fine.

You should also take precautions to try to protect your lawn and any plants. Bleach can potentially harm or kill plants and foliage.

Cover your plants and your grass to keep the bleach from ruining things. You should be able to get the job done in time.

Those who don’t like working with bleach will have other options, though. You could buy cleaners that are specifically meant for killing mold, mildew, and green algae.

Some of these cleaners might be safer to use than bleach. It’s up to you to decide which method is the most practical.

Sand the Fence and Apply Primer

Sanding the fence and applying primer is a great way to protect it. You won’t have to worry so much about mold issues if you take the time to do this.

It’ll take some time to get this job done, but it’s worthwhile if you’re tired of having to worry about mold. Simply get a sander and start sanding the fence down.

To make things go faster, it’ll be a good idea to buy an electric sander. Manual sanders will work fine, too, but they will take a lot longer to finish this job.

Be sure to take your time to thoroughly sand each board on the fence. You don’t want to move forward until everything is truly done so that you can get this job done properly.

When the fence is sanded, it’ll be time to apply some type of primer or sealing agent. This will protect your fence by making it so that bacteria cannot penetrate it.

Doing this should make it so that you won’t have to worry about mold, mildew, or green algae for a long time. This is highly recommended so that you can protect your wooden fences from harm.

The only problem is that you must be certain that you cleaned off all of the mold first. If you left any behind, then it could cause you more problems.

Applying a sealant or primer when mold is still present will be problematic. It can grow under the sealing agent or primer and keep causing damage to the fence.

So just make sure that you remove all mold, green algae, and mildew from the fence. Being thorough when sanding it should be enough to keep things safe.

Paint the Fence

Of course, it can also be helpful to paint the fence to prevent issues with mold. This will also require sanding it, but it’s going to be worthwhile to do.

You can keep mold from being able to grow on the fence by protecting it with primer, and then you can paint it. To get the proper results, you’ll need to use outdoor paint.

Outdoor paint is formulated to last as long as possible in an outdoor environment. Indoor paint simply won’t work as well to do the job.

You should know that this paint job won’t last forever. It’s going to be necessary to paint the fence again two or three years down the line.

This is something that you’ll keep having to do if you wish to protect the fence from mold issues. It isn’t difficult, but it will require you to continue maintaining the fence.

Build Fences Using Different Materials

Of course, you could simply build fences using other materials so that you won’t have to worry so much about mold. There are many different ways to make fences for your property, after all.

You might wish to consider making a fence using brick or vinyl. Some also like to use metal to make very sturdy fences.

Mold can still be an issue when using materials such as brick and vinyl. It just isn’t quite as bad because mold won’t be able to damage the internal structure of these materials.

You can clean brick and vinyl fences fairly easily. They’ll just need to be wiped down and sprayed from time to time to keep them looking nice.

Metal fences are very practical, but they do have their own issues. For example, metal fences can rust over time due to moisture exposure.

If you’d still like to use wood for your fence, you might want to think about using pressure-treated boards. You can purchase pressure-treated boards from the hardware store.

These boards have undergone pressure treatments that help them to resist water retention. They won’t be damaged by water retention in the same way as standard wood.

It’s also nice to use pressure-treated boards because they can’t be eaten by termites. You might save yourself a few headaches if you choose to use them to build your fence.

Final Thoughts

Wooden fences turn green because they’ve become moldy. Mold, mildew, and green algae can form on fences when they’ve retained too much moisture.

There are many ways that you can go about trying to solve issues with mold. It’s going to be important to try to take care of things fast, though.

Allowing mold or mildew to remain on a wooden fence will weaken it. You don’t want it to become unstable or it will start to fall apart.

Thankfully, you can try to clean the mold off of the fence using a pressure washer. This is a very fast way to take care of the issue, and it’s a good reason to invest in one in the near future if you don’t already have one.

You could also clean the fence by scrubbing it manually with a brush. Using bleach and water in a bucket is a solid idea.

It’ll be necessary to protect the grass and any nearby plants, but you can get the mold off of the fence using bleach. Conversely, you could purchase cleaning products that are meant to kill mold and mildew.

Sanding the fence and then applying primer or a sealant could work, too. You could also try building a fence out of different materials so that you won’t have to worry as much about mold issues.

Decide which route makes the most sense for your situation. You can easily solve your green fence problem so long as you put in the effort.


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