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The Home Depot

Causes of Mildew on a Wood Fence

Pro Referral > Home Guides > Fence > Causes of Mildew on a Wood Fence
Causes of Mildew on a Wood Fence

Wood fences are very picturesque and can lend an elegant look to your home and property. However, they also need a considerable deal of maintenance to keep them looking as good as new. One common problem that afflicts wooden fences at one time or another is mildew. Inspecting your fence regularly will help you spot early signs of mildew and take the necessary steps to do away with it before it spreads all across the fence (and possibly your home). The first signs of mildew are black, gray, or brown spots on the fence and paint.


Permits are needed when installing any kind of fence on your property. There are certain specifications about the height of the fence, the width and length as well as the materials that can be used. This will vary depending on the location where you reside.

  1. The presence of moisture or humidity, lack of sunlight, plant growth, dirt, and inadequate sealing are the common causes of mildew.

    1.Common Causes

    Once you know the different causes of mildew, you will be able to adopt precautionary measures to ensure that it does not affect your wooden fence. The presence of moisture or humidity, lack of sunlight, plant growth, dirt, and inadequate sealing are the common causes of mildew.

  2. 2.Moisture and Humidity

    Mildew flourishes in places where there is sufficient moisture and enough nutrients for the spores to grow. Surface dirt is more than enough to fulfill the food requirements of mold. Increased humidity leads to excess water vapor which can penetrate the wood on the fence and cause mold spores to germinate. The spores breed and cause mildew to form on the surface. Since the humidity outside the home cannot be controlled in any way, you can only paint the fence with a fungicidal paint or sealant to minimize chances of mold and mildew.

  3. 3.Insufficient Sunlight

    If the wooden fence on your property is in a shady spot where it does not receive sufficient sunlight each day, then it can soon turn into a breeding ground for mildew. This is because the absence of sunlight can increase the presence of condensation and moisture left behind by rain and fog. This moisture gets into the wood and can stay there for a long time since sunlight will not evaporate it. This easily enables the mildew’s roots to grow and slowly take over that portion of your fence.

  4. 4.Foliage

    If there are many plants or vines growing over your wood fence, it can prove to be a conducive environment for mold and mildew. The thick growth of plants can prevent air from circulating which in turn prevents the accumulated moisture from evaporating. Also, plants often have fungi on them which include a variety of mildew. This plant mildew can be transferred or leapfrog over to your fence.

  6. 5.Inadequate Sealing

    Sealing of wood fences is important to keep them free from moisture and mildew. Using a hardy and quality sealant will prevent moisture from getting into the wood. Wax sealants can be quite ineffective in preventing this from happening, so it is better to avoid using it. If you have sealed your fence when it was installed, be sure to keep repeating the process at least once a year. You can use a paint sprayer to help with the resealing.

  7. 6.Dirt

    Dirt nourishes mildew. So, keeping the wood fence clean at all times will act as a deterrent to mildew growth. Using a solid and tremendous cleaner and power washing the fence is an effective method of dirt removal. Acid-based cleaners are recommended for fence cleaning rather than alkaline cleaners because they pose fewer hazards to the user. But they are also not as effective as the alkaline cleaners. Never let the cleaner dry on the wood because then you will not be able to use a sealant. Light pressure must be applied when cleaning, the right cleaner should be used, and then washed with large amounts of water.

  8. 7.Different Environments

    Ensuring that your wooden fence is in sharp and striking condition is one way of increasing the value of your home and property. Greater care needs to be taken if you happen to live in places with environmental conditions that are more favorable to the growth of mold and mildew.

  9. Related: Top Causes of Fence Rot, Fence Repair Services

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