Why Your Fence Turns Green (Causes and Fixes)


Wood fences are beautiful and should stay that way! So, what happens if it doesn’t? 

If a wood fence is turning green, it’s because there is green algae, mold, or mildew growing on it. This is caused simply by the wood pickets retaining water. A few quick fixes are to power wash it, scrub it down, or sand and prime it. 

A green fence is no ones favorite, but cleaning a fence is possible. Keep reading to figure out to get your fence back to normal.

Why is My Fence Green?

There are a few different reasons why your once beautiful fence is now turning green. The three main culprits are:

  • Green algae
  • Green mold
  • Mildew damage

Green Algae

Green algae is a harmless fungus that grows on wet, shady surfaces. It’s a bit hard to avoid this issue just because we can’t control the weather!

Luckily, the presence of green algae won’t damage that integrity of a wood fence, at all. Sadly, it’s not very attractive to look at especially compared to the beautiful natural wood fence you started with.

Mold

Mold is a bit trickier to deal with than the green algae. Mold is also a fungus, but the bacteria can cause some damage to the wood if it’s left for too long.

Mold grows when the wood pickets on the fence retain water and have no way to expel it. Just like the algae, it’s a bit difficult to prevent because weather is unpredictable.

If mold is present, it should be removed quickly so no damage occurs.

Mildew

Mildew is basically the same thing as mold. The good news is, it’s not as harmful to the fence pickets.

Now, it’s not as innocent as green algae, and it won’t cause as much damage as mold. It should still be removed as quickly as possible.

How Do I Fix My Green Fence?

There are a some pretty easy ways to get your fence green-free, all of which should be done sooner rather than later.

Power Wash

No matter the reason a wood fence is turning green, a good power wash should alleviate the issue, temporarily. This process may need to be repeated a couple of times a year.

This method is only effective if the mold and mildew haven’t caused any internal damage to the fence pickets. If the wood is cracked, eroded, and falling apart, power washing won’t do much.

Also, if you decide to use a power washer, make sure you use a bleach solution. That’s the only way to kill the bacteria growing on your fence.

Before you wash your fence, all plants and grass need to be covered with tarps or plastic coverings to avoid damage from the bleach solution.

Scrub Brush

If there’s no access to a power washer and you’re feeling ambitious, a good scrub job should do the trick!

Any scrub brush will do, really.

Regular kitchen sponges are not recommended if you choose this method. They are not nearly as effective; the fibers will get caught in the wood grain, and the sponge will rip apart after just a short time.

Just like with a power washer, you’ll want to use a bleach solution with this cleaning method. Dish soap is not recommended since it won’t kill the bacteria growing on the fence.

Again, make sure to use preventative measures before using the bleach solution in the yard.

To protect yourself, wear long sleeves, long pants, close-toed shoes, and rubber gloves. This helps avoid any skin irritation from the bleach.

It’s not as imperative to cover the plants and grass around the fence when using a scrub brush since it’s easier to manage the bleach solution cleaning by hand. If anything, cover the grass that you’re working on, just in case any of the solutions drips or spills.

If you don’t like the thought of using bleach on your fence, there are cleaners and chemicals marketed for this issue, specifically. Here are a few of them in action:

Sand and Prime Fence

This method is a bit more time intensive, but can be very effective!

It doesn’t matter what grade of sandpaper you use, but it is a bit easier if you have an electric sander rather than just sanding the fence boards manually.

Once each board is sanded thoroughly, you’ll want to go over each one with some sort of primer or sealing agent. This will ensure no bacteria can penetrate the wood boards in the future, which means no more green stuff!

If you do choose to sand and prime the fence, make sure you sand ALL the algae, mold, or mildew off. If there’s any left behind, it will continue to grow under the sealing agent and cause further damage. Your effort will be all for naught.

Take Down and Re-Install

There are a few ways to help avoid this issue altogether, especially during the rainy and cold times of the year.

One of them is to simply tear down the fence every fall, store the materials in a covered, dry spot, and re-install it every spring.

This method isn’t recommended very often, especially since wood isn’t very forgiving, nor is it easily manipulated. It is also very time-consuming to this every year.

Re-installing the fence doesn’t absolutely prevent the wood from collecting algae or mold since weather can be unpredictable. You may still have to use other methods during the time your fence is up.

Install a new fence every year

If you choose to install a new fence every year, you’ll need to purchase all new materials, re-plan the perimeter, re-dig the holes, etc.

If you have plenty of time and money, this method is not recommended and you should just choose one of the many other options provided.

Use Different Fence Materials

Rather than a wood fence, you could install vinyl, brick, metal, or steel.

Installing a vinyl or brick fence won’t eliminate mold and algae. However, these won’t cause any internal damage as it does on wood fences. And, vinyl and brick are a lot easier to clean and restore than brick.

Just give them a nice spray down and you’re done.

If you don’t want to deal with mold or algae at all, then metal and steel are the best options for this. You can avoid the green problem, but water does cause rust to form on these types of fences. So you’re trading one issue for another.

But: there will be no green stuff in sight.

How to Avoid the “Green” Issue

All wood fences should come with a disclaimer about the maintenance.

If you choose to install a wood fence, just expect to have to clean it up, maintain it, and remove algae, mold, and mildew; that issue just comes with the material.

That being said, there are a few ways to avoid the issue altogether, at least for a time.

Heat-Treated Wood Fence Boards

Another way to avoid the “green” problem is to heat-treat the fence boards. This is a pretty simple procedure and helps in a lot of ways.

Since the green stuff is caused mainly by water retention, heat-treating the fence could help alleviate the issue.

If you apply high heat to the fence boards, this almost seals the fibers and makes it very difficult for water to penetrate the boards. No penetration means no retention.

This can be done with a heat gun but is difficult to do without any prior or proper training. Heat-treated wood can be purchased prior to installing your fence.

Pressure-Treated Wood Fence Boards

Pressure-treated wood is made specifically for outdoor use; usually decks and fences.

You can’t pressure treat wood yourself, it has to be purchased. This wood undergoes a series of pressure treatments where water and preservative agents are embedded deep into the wood. Once the water evaporates (usually after a few weeks) the preservatives stay in the wood.

This helps keep the integrity of the wood, keeps termites and bugs at bay, and helps the wood resist any water retention and damage.

Prime and Paint

Another simple solution is to prime and paint the fence boards. This is an easy way to help avoid your fence turning green. Make sure you use outdoor paint so it lasts a bit longer.

This method does require a bit more attention and will need to be repeated every 2-3 years. Paint tends to chip and flake off, which can lead to water retention and damage.

Stain and Seal

If you don’t like the look of paint and want to keep the natural wood look, just simply sand the fence boards and place a stain, sealant, or lacquer on them.

This method, just like heat-treating, seals the wood fibers and makes it extremely difficult for water to penetrate the boards. Stain tends to last longer on wood since it’s absorbed into the wood rather than just a layer on top of it.

There are special water-resistant stains, as well, to help avoid the issue altogether.

In short, don’t worry too much about your fence turning green. There are ways to remove it, to restore your fence, and ways to help avoid it altogether!

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