How to Prevent Wood from Rotting in the Ground

Wood is used for various purposes, but wood rots can be discouraging, and as a result, you might have your fence posts, and wooden railings weakened and falling off. Having your wooden posts rot away is not desirable as you’ll always have to change your fence posts every few years. This article contains everything you need to know about how to prevent wood from rotting in the ground.

Moisture and warmth affect the wood so that it weakens it, makes it more porous, and eventually increases its surface area, which makes it a site for biological infestation, which ultimately causes wood rot. Using pressure-treated wood is an excellent way to prevent wood rotting as it contains chemicals that make the wood resistant to biological attack.

Although some might not like the choice of a pressure-treated wood as it contains arsenic and chromium, instead, there are other wood preservatives such as linseed oil, creosote, and water-borne naphthenate, which are also efficient against wood decay.

Factors that affect wood rotting in the ground

  1. Exposure to moisture
  2. Repeated exposure to moisture causes the wood to start rotting as the structure breaks up, causing it to weaken and increase its porosity, making it more vulnerable to biological attack.
  3. Type of wood
  4. The type of wood affects the rate of decomposition. For example, a greenwood is more susceptible to rot than a pressure treated wood, which is decay-resistant. Woods also decays at different rates, and their decay resistance varies. Using non-treated lumber for fence posts won’t last long as it won’t resist biological attack.

How to treat wood for ground contact

The best preservatives to use are chemical preservatives that prevent or slow down the rate of decay and biological infestation on the wood. The most common preservatives are pressure treating the wood with creosote, pentachlorophenol, and inorganic arsenic compounds such as Chromated copper arsenate (CCA). These chemicals preserve and protect the sapwood.

It is advisable to seal pressure treated wood after it has been sawn. The ideal preservative to use, which we highly recommend, is water-borne copper naphthenate, a wood preservative-free of arsenic and chromium. Even if you’re using pressure-treated lumber, it’s still advisable to brush this copper naphthenate on it before use. This will protect the wood from rotting.

Steps on how to treat your wood to prevent them from rotting

These simple outlined steps will guide you on how to treat your wood, significantly fence posts, from rotting in the ground, and most especially if you want to install new posts. These steps will guide you on how to treat the wood to make it rot resistant.

Step one: Dry the wood

Place the wooden fence posts in a cool, dry place with a lot of ventilation to make the wood dry. If your wooden posts are already dry, then you don’t have to dry them again. But when using green wood, you have to dry them thoroughly due to the moisture content present in the wood that encourages decay, and the moisture content present in the wood won’t allow it to take up much liquid wood preservative. The drying might take months if you’re using greenwood.

Step two: Choose the type of preservative you want to use

It’s necessary to choose the type of preservative you want to use, either pressure treated lumber, creosote, pentachlorophenol, or water-borne copper naphthenate. We recommend using water-borne copper naphthenate, which is free from chromium and arsenic and safer to use.

Step three: Brush the bottom half of the wood with the preservative.

Brush the bottom third or half of the lumber or fence post with the water-borne naphthenate. Brush the preservative on the entire wood or post if you desire, but the bottom must be well treated because of the buried part of the wood rot much faster than the amount above the ground. You can apply the preservative in another way by placing the wood upright in a bucket filled with the wood preservative. Still, this application method is not that effective when you have to treat various woods and fence posts.

Read Also: Is Pressure Treated Wood Safe for Vegetable Gardens?

Step four: Allow effective absorption

After brushing the wood, wait for about one hour to allow the copper naphthenate to absorb into the wood, then apply a second coat and wait for an hour for it to soak in the wood. Continue brushing additional coats of copper preservative on the wood until the wood stops absorbing, which implies that the preservative has worked its way through the sapwood, including the heartwood.

Step five: Allow drying

After applying the preservative, allow the wood posts to dry.

Step six: install your wooden posts.

Dig a hole two to three times the fence post’s diameter and 24 to 48 inches deep. Make sure the wood posts stand upright, then bury one-third of the total post length. You don’t necessarily have to dig deep. Twenty-four inches deep is okay. While placing your wooden posts in the hole, make sure a part of the copper naphthenate treated wood is exposed above the ground.

Fill the hole with about 6 inches of 1/4-minus gravel. I’m sure you’re wondering why I’m suggesting 1/4-minus gravel? Well, the stone is better because it contains small gravel pieces and gravel dust for better compaction, and it allows water to drain from the fence post into the soil. You can use concrete, too, but the concrete’s moisture might cause the wood to rot quickly.

Pack the gravel tight to form a level base with the blunt end of a digging bar or a hand tamper. Set the post in the hole while holding a level on the side to check for plumb. Fill the gap and the wooden base with more gravel packed tight against the side of the post. Then tamp down the stone and push the soil around the fence post to conceal it.

The soil containing moisture around the fence post can cause the wood to rot. That is why it is necessary to brush the wooden post above the ground with preservatives. Ensure to build-up the soil so that it is at a slight slope around the wooden post to improve drainage and prevent water-storing around the post. Then cut the fence tops to desired heights using a reciprocating saw, ensure to cut at a slight angle so that it’s easier for water to run off at the edges.

Step seven: Brush the top part of the wood.

Brush the top parts of the fence posts with the wood preservative, especially the fresh cuts. Once the first coat absorbs into the wood, apply an additional coat.

Step eight: Take care of the cracks

take note of any damages on the fence post and brush copper naphthenate preservative on it and make sure it penetrates deep into it.

Step nine: Air-dry

Allow all the wooden posts, fence posts, and rails to air-dry for a few months before applying paint, sealant, or stain on it. If your wood was dry before using a preservative, you could apply your paint right away but make sure the wooden rails are completely dry.

Step ten: Paint

After you’re sure the wood is dry, then you can paint using latex paint, which is an oil based stain that prevents the wood from weathering and increases its durability at the same time.

Other methods of wood treatment

The other forms of treating wood, apart from using tagged wood, inorganic chemicals, various preservatives contain antifungal chemicals and insecticides. Examples of these preservatives are linseed oil, creosote, and different other commercial preservatives that prevent the wood from rotting. They protect the wood’s outer surface, and they’re applied to the surface of the wood by painting or spraying.

The only difference they have is that they are not as durable as pressure-treated wood and naphthenate, and they have to be reapplied after a few years.

Using linseed oil

You can also treat your wood using linseed oil. For this method, we will be using tung oil and linseed oil gotten from the tung tree and seeds of the flax plant, respectively. These two oils are mostly used to create a warm, hand-rubbed finish and have been used over the centuries for their great functions as they protect the dark-grained woods such as walnut and mahogany.

We can mix the two oils with a few other vital ingredients to make the perfect solution to treat your outdoor wood and the untreated wood pieces. You can either buy pre-blended linseed and tung oil or buy them separately and mix themselves. A standard hand-rubbed oil mixture consists of either of the two oils, one part polyurethane, and one part mineral spirits. Here is the method on how to go about the mixture:

  1. Mix and stir all the ingredients thoroughly.
  2. Use a natural bristle paintbrush to apply it to the wood pieces.
  3. Allow the oil to get absorbed into the surface. After that, you need to reapply another coat to the spots that look dry.
  4. Wipe off the residual oil using a dry towel or rags. This will remove all the excess oil from the surface.
  5. To Let the wood dry completely, this can take up to a few hours or preferably overnight, depending on the mixture’s amount of oil.

Tools and materials required

  1. Wide paintbrush
  2. Water-borne copper naphthenate
  3. Wood preservative
  4. Measuring tape
  5. Reciprocating saw
  6. Exterior latex paint
  7. Small paintbrush
  8. Natural bristle paintbrush
  9. Posthole diggers
  10. Linseed oil
  11. Hand tamper
  12. Digging bar
  13. 1/4- minus gravel
  14. Exterior oil-based wood stain.


  1. Make sure the wood you want to use is dried thoroughly
  2. In case you’re using pressure-treated wood, apply a preservative cost at the bottom end of the post. This will increase its resistance to rot.
  3. When working with a copper naphthenate, always wear goggles, breathing masks, and gloves and ensure you work in a well-ventilated area. Working outside is most preferable.
  4. In case you’re using green wood that has been dried, make sure you add several coats of wood preservatives until it doesn’t absorb again.

Conclusion – How to Prevent Wood from Rotting in the Ground

Untreated wood is not resistant to rot, and generally, they’re much more prone to biological attack and infestation. It is necessary to prevent the wood from rotting in the ground and employing various methods and guidelines to avoid decaying. You can use pressure-treated wood for your outdoor purposes. Perhaps you don’t want to use pressure wood to use water-borne copper naphthenate wood preservative to coat your wood to make it resistant to decay and biological attack.

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