One of your biggest worries is how to prevent wood from rotting in the ground. You don’t want your fence or deck to deteriorate quickly and turn ugly, or worse, cause an accident.

Fortunately, there are ways to ensure your woodwork can withstand the elements longer. Rain, hail, storms, and extreme heat may come, but your decisions and action can make your wood project resilient. 

Here are tips and techniques to prevent rot on wood. With these, you’ll be sure that your fence or wood will remain sturdy and looking great.

How To Prevent Wood From Rotting In The Ground

Protecting your wood from rotting isn’t rocket science. It’s as easy as soaking the bottom of your untreated fence post or deck planks in a wood preservative, painting your wood, installing the fence posts properly, and using wood treatments such as copper naphthenate.

What Causes Wood to Rot?

Wood rotting is caused by a combination of fungus, moisture, oxygen, temperature, and wood, which serves as the fungus’ food. Amongst all those causes, it is moisture that we can control and moisture that fungi needs. 

Simply put, fungus needs moist wood for it to develop. That’s why fungus won’t grow on dry wood.

The fungus can come from the soil that can infect the wood upon contact or through the air, as there’s no such thing as airborne fungus.

When fungus does grow on a piece of wood, it can infect another, otherwise, healthy wood.

But now that we know how fungus grows, we are not helpless in preventing the wood from rotting.

Choosing the Right Kind of Wood for Ground Contact

The first step is to choose the right type of wood. 

Go for heartwood

Trees that have a lot of natural oils and extractives and heartwood naturally make rot resistant wood.  They don’t allow fungi to grow. Heartwood refers to the tree’s inner core. It’s here that we find compounds  (called extractives) that fight fungi and make naturally rot resistant wood.

Extractives give the tree its color, scent, and other characteristics.

Other factors are the density and how hard the tree is, as these can keep insects and moisture out.

There’s no type of wood available in the market safe from rot, except for the heartwood of some varieties. This is because almost all trees come from a second generation that contains a lot of sapwood. Sapwood is susceptible to decay and fungi growth.  

Despite this, we can choose to build with types of wood known to be dependable, prevents fungi growth, and will not rot for a long time.

Rot Resistant Wood


This has a natural wood preservative that repels termites, moths, and other insects. Its natural oils kill fungi, so much that people use cedar oil to get rid of acne and other skin blemishes.

The natural oils in cedar also make it waterproof. These are the favorite cedar varieties among builders:

  • Western Red Cedar
  • Yellow Cedar
  • Spanish Cedar
  • Northern White Cedar

Cedar is ideal for wooden rails, wooden fences, bench, among others.


Redwood’s trunk is mainly made of heartwood, making it naturally resistant to rot. Heartwood refers to the tree’s inner core. It is here that we find compounds (called extractives) that fight fungi and protect the tree from insects.


Because of its strength, density and toughness, it can stand up to water and insects. It’s a popular choice for making doors and outdoor furniture.

These are among the top types of wood that have a natural preservative against rotting. The problem is, their durability and anti-rot properties translate to higher prices.

Alternatively, you can choose to purchase pressure treated wood.

Pressure treated lumber

It’s still possible for pressure-treated lumber to rot, but it lasts longer and is less expensive than lumber from heartwood and the above-mentioned tree species.

Again, there’s no type of pressure-treated lumber that will not rot. Yes, they contain a liquid wood preservative that makes them rot-resistant, but they aren’t water-resistant. They can still get soaked and lose moisture. Eventually, they will get cracks, twists, and get bent which is why you need to know how How To Protect Pressure Treated Wood Underground.

Just a reminder: when working with this type of wood, it’s best to wear protective equipment (dust mask, goggles, and gloves) to avoid prolonged exposure to the chemicals used to treat the wood. Work outdoors or in a well-ventilated area.

Goodbye CCA

Previously, chromated copper arsenate (CCA) was used to treat wood. CCA is an inorganic arsenic pesticide that protects wood from rot and pests. This was phased out in 2003, as its chemicals (chromium and arsenic) were harmful to people and could contaminate groundwater and soil.

Fortunately, there are wood preservatives that are non-toxic and equally capable of protecting wood from decay and insects.

Pressure treated wood that are decay resistant

Alkaline Copper Quat (ACQ) treated wood 

ACQ is a water-based wood preservative that prevents rot and repels insects. Still, this type of treated lumber may crack, shrink or warp.

ACQ wood has very low to moderate toxicity when inhaled, gets in contact with skin, and inhaled. It can also cause minimal eye irritation. ACQ treated wood is available as brown or green wood.

This can be used as fence posts, decks, utility posts. It can also be used indoors for studs, beams, and frames. Just make sure the wood does not contact food or around the fish and other living creatures in your aquarium.

Read: How long does pressure-treated wood last?

Copper naphthenate treated wood

It’s emerging as a popular choice for outdoor projects. Copper naphthenate preservative has been classified as a General Use pesticide by the Environmental Protection Agency. Thus, it does not only prevents rot but kills termites. It’s less destructive to the environment.

The copper naphthenate preservative appears as bright green wood that turns into light brown over time. It also has a distinct smell that eventually fades. It is best to use protection such as gloves and goggles when handling this treated lumber with its chemicals and odor.

Copper naphthenate preserved lumber is commonly used for utility posts, docks, seeding trays, and greenhouses.

Borate treated

This type uses boric acid, a combination of naturally occurring minerals that protect against rot and biological attack (termites, ants, roaches, and beetles).

This is used indoors. Borate is commonly applied to studs, sill plates, joists, plywood, and sheathing.

It’s not recommended for outdoor use, especially in areas that can be reached by water or rain. When soaked, chemicals in the wood may be washed out onto the surface area and then to the soil. It must not be used as material for a dining table, as it should not contact food.

How to Prevent Wood from Rotting in the Ground

If you didn’t purchase any of the above-mentioned types of wood, bought untreated wood, or have already installed your project, don’t worry. There are still ways on how to prevent wood from decaying when below ground.

Soak the bottom of your untreated fence post or deck planks in a wood preservative.

Here’s what you’ll need:

  • Wood preservative with copper naphthenate. Make sure this meets the American Wood Protection Association standards.
  • Large bucket
  • Paint brush
  • Googles
  • Gloves
  • Face mask

Steps in applying a wood preservative

Before starting the process, make sure the untreated, fresh wood is dry. Then:

Step 1: Wear your protective equipment.

Step 2: Pour half a liter of the preservative into a large bucket.

Step 3: Soak around 1 ft of the entire post or plank for 20 minutes.

Step 4: Brush the preservative on the entire wood surface.

Step 5: Allow it to dry for about one hour.

Step 6: Continue brushing additional coats (and let dry accordingly) until the wood stops absorbing the preservative.  Never mind the thick layer. You need to ensure that the preservative has reached the heartwood.

Step 7: Allow it to air dry.

Paint the wood

 Applying paint and sealing the wood will keep it dry. Ideal to use latex paint to make the wood more durable.

But can pressure-treated wood be painted? Make sure to confirm if it’s possible in case you’re working with treated lumber.

Install fence posts properly.

Fence builders will tell you that there is a surefire way to prevent the fence posts from rotting.

Steps in installing wooden fence posts properly

Step 1: Dig a hole about twice the fence post’s diameter of each fence post and as deep as a quarter of the total post length. These measurements ensure that the fence will be secured and the post upright and prevent fence posts from rotting. Ideal to use a post hole digger so that you’ll have the ideal size of your fence posts.

Step 2: Fill the hole with three inches of gravel and gravel dust. Make the gravel tight to prevent your wooden posts from touching the soil.  Plus, gravel allows water from the fence posts so that they drain quickly.

Step 3: Place the wooden post in the center of the hole.

Step 4: Fill the entire hole up with cement to the top. Concrete will hold the wooden posts firmly in place. Make sure the cement fills up the hole until the ground level. If you don’t pack the cement, unwanted moisture may come in, and the process may not prevent fence posts from rotting.

Apply other wood treatments

Besides copper naphthenate, you can apply other antifungal chemicals and insecticides. These include creosote and linseed oil. The difference is, you need to apply these every few years to ensure wooden fence posts or deck is protected.

Things you’ll need and techniques to avoid wood rot

Make sure water flows away from your fence post or deck plank.

Granted that a deck and a fence post usually get wet, but is there a way for water to flow somewhere else and not get stuck underneath.

For decks, you can put bricks or pour cement under the deck. The ground should have a slight slope that would let water flow away from your home.

Keep every fence post/deck plank clean.

You don’t want grass, dirt, dust, and mulch to accumulate on your deck or wooden fence posts. Best to regularly clean these. You can use a power washer to make cleaning easier and ensure you get rid of all the unwanted dirt.

Use baking soda.

Its cleaning properties will give your fence post a deeper clean.

Seal pressure treated wood periodically.

Again, this is to protect the wood from the effects of water – mildew growth, warping, and splitting.

Use baking soda.

Its cleaning properties will give your fence post a deeper clean.


With these tips and techniques, you can be an expert on preventing the wood from rotting in the ground. What’s important is an understanding of the elements that cause wood to rot. And how to keep the said elements from accumulating and getting stuck in the wood.

It’s equally important to keep your deck or fence clean to prevent fungi from growing or moisture from dwelling on the wood. Take care of your project so it will not get rot quickly.

Further read: Will Bleach Stop Wood Rot?

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