Skip to Content

Why is My Fence Turning Black?

If you are interested in finding out what is on your fence, this is the right article for you. We will also discuss the ways to remove what is growing on your fence to improve the overall look of your fence.

Close up of fence with black mold on it

A fence is an excellent addition to your outdoor space. It can add value and privacy and give your yard a finished look. Fences do, however, require some care. For example, have you noticed black areas on your fence?

As a general rule, when you see black marks on your fence, it is mold and mildew. However, there is a chance the black marks are green algae, water stains, or dirt. Understanding what it is determines how to clean it.

If you are interested in finding out what is on your fence, this is the right article for you. We will also discuss the ways to remove what is growing on your fence to improve the overall look of your fence. 

Why is My Redwood Fence Turning Black?

Close up of  redwood fence

Several things could cause black stains on a redwood fence. It could be mildew or tannic acid. Redwoods contain tannic acid, which makes them resistant to bugs. However, when this acid comes into contact with metal, it causes a black stain. 

Mildew can also be the cause of black or fan like spots on the surface of redwood. When the mildew is severe, it causes areas to appear completely gray or black. When the black mold on fence is mild, you may be able to scrub the surface with water mixed with a mild detergent. 

If that does not work, you may need to combine bleach with water and scrub the area. After scouring the fence with the bleach mix, it should be rinsed off with water. 

Oxalic acid crystals mixed with warm water may work if that does not work. When you combine these items, do so in a non-metal container. You should use a soft brush to apply this mix and once the wood is dry, rinse it off with water. 

Why is My Bamboo Fence Turning Black?

Close up of a bamboo fence

While a bamboo fence is an attractive option for your yard, bamboo does face some common problems. These problems include peeling, splintering, and mold. When you have black spots on your bamboo fence, the mold’s fungal spores have spread and caused damage to the fence. However, there are steps you can take to prevent mold from taking over your fence. 

Ensure that your fence gets a good amount of sun because mold cannot live and grow in sunlight. You can use a fungicidal sealant on your fence. You paint it on the fence, especially when you live in humid or damp areas.

Once mold has begun to grow, combine bleach, water, and dishwashing detergent without ammonia in a spray bottle and spray your entire fence with it. After letting that sit for about 15 minutes, rinse the whole fence with your hose.

Pressure Treated Wood Turning Black

Close up of a natural wood fence thats been pressure treated

When pressure treated wood turns black, it means it has a fungal issue and is rotting. This fungus consists of small organisms that feed on the wood. This causes the pressure treated wood to soften and decay. After this happens, the wood begins to rot. This tends to happen once the woof gets wet and stays wet for an extended period of time while it is stored. 

It is essential that pressure treated wood is cleaned and dried before it is stained. A quality wood cleaner should be used with a pressure washer or scrub brush. This helps to remove mold, mildew, black and gray spots, as well as dirt. 

The wood should be completely dry before any staining occurs. However, the chemicals in the stain that is used to treat wood do allow some moisture to stay on the wood. 

When there is black mold on fence that is made of pressure treated wood, there are some steps you can take to remove the mold. First, you can scrub the mold stains with a combination of water and bleach. This kills the mold. Using a soft brush, scrub until all signs of mold go away. After you scrub the surface, allow it to dry, so the bleach mixture soaks into the surface and dries. 

How to Clean A Black Fence

Close up of fence boards with black mold

If you have mold growing on your fence, you want to clear everything away from the fence. Any vegetation, trees, and brush should be cleaned from the fence. The way you clean your fence depends on the type of fence that you have. 

If you have a wood fence, you can start with water and a scrub brush. If that does not work, you can mix mild detergent and water with a soft scrub brush. If you find that this takes too much effort, you can use a pressure washer. It is important to keep it in a low setting. If the setting is too high, you might damage your fence. 

If these methods do not work, you can try mixing bleach and water to scrub the mold away from your fence. If these tips do not work, it could be the tannins in the wood. It may need to use oxalic acid combined with warm water to scrub away the mold. 

If you have a vinyl fence, you can use a vinyl cleaning solution and a soft cloth to clean the fence. If this does not work, mix white vinegar with water in a spray bottle and soak the fence with the solution. Allow it to sit on the fence for 15 minutes before you scrub the fence and rinse it away. 

If none of these options work, you could use some baking soda on the vinyl fence to remove the mold. No matter which option you choose, pick a day that is sunny and warm. This helps the fence dry faster and prevents mold from growing back. 

How To Stop My Fence From Turning Black

There are several steps you can take to keep your fence from turning black. The first step you want to take is to remove everything from around your fence. You want to get rid of vines, brush, and other things that rub up against your fence. This keeps items away from your fence that can cause moisture on your fence. 

All of this vegetation can prevent the sun from shining on the fence. Sun can prevent the growth of mold. In addition to allowing the sunshine on the fence, you can stain it to help prevent the growth of mildew and mold. You can select a stain that is a UV blocker. You can spray or brush it on the fence as long as the stain soaks into the wood. 

You may need to stain the fence every couple of years. In addition to staining the fence, you can provide regular cleaning and maintenance on your fence. During regular maintenance, you want to ensure that all brush and trees are trimmed back, so they do not come within one foot of the fence. 

Your fence can also benefit from regular cleaning. You can use a solution of one part bleach and three parts water. You want to spray the fence with the bleach mixture and then spray it again with water. When cleaning your fence, you want to make sure that you check it for areas where mold is growing.