How to stop wood rotting outside?

Wood is an environmentally friendly and durable material widely used for the construction and decoration of residential buildings and outbuildings. One of the few disadvantages of wood is its susceptibility to decay in the ground.

To increase the life of building materials, it is important to treat wood promptly with compounds that reduce the negative impact of moisture. You can use both traditional and trusted folk methods. We will figure out how to treat pressure treated lumber from rotting and moisture on the street and protect it from negative environmental conditions.

how to stop wood rotting outside

What kinds of wood are more rot-resistant?

If you don’t want your wooden fence posts to rot, then you must use naturally resistant wood for your outdoor projects.

Here we have a wide choice of wood types that would not rot quickly:


An example of such a material is oak. It resists adverse environmental influences. It is not spoiled by a fungus, wind, sun, or water. In contact with water, on the contrary, it only becomes stronger and acquires a darker shade.

Oak is difficult to process, it is difficult to give it a certain shape. It practically does not crack and does not warp.

The older the oak tree itself, the better it’s wood.

A nice type of decay resistant lumber for installing fence posts or any other outdoor structure overall!

The only downside is its cost – oak is significantly more expensive than other types of lumber.


Slightly less affordable, durable, and resistant to rotting wood is larch. This is a coniferous tree with a straight trunk.

It practically does not rot and is not exposed to blue fungus or moisture or rotting in the ground.

This lumber type is less affected by insects and fungi, due to the characteristics of its resin, which performs an antiseptic role.

Larch has an interesting texture, and after processing the material looks beautiful.

The natural shade of this decay resistant wood is dark brown.


It belongs to soft rocks, it is easy to say, plan, and process for your wood posts (such as fence posts) or any other wood project.

This wood has a straight and even trunk.

Pine does not crack much when it dries.

It has a yellowish-white tint, a distinct texture, and a high resin content, making it resistant to rotting in the ground. A great choice for a fence or deck.

There is also ship pine, it is not afraid of moisture, and it is actively used in shipbuilding. It differs from ordinary pine in a higher and even trunk. And its resinousness depends on the time of year and the age of the tree.


The tree has a smooth, straight, round trunk. It is more difficult to process due to the hardness of the knots present, even though the lumber itself is soft.

Still this lumber is highly resistant to rotting in the ground contact, with even untreated wood being resistant to fungi.

This rot resistant wood has a looser texture and is warmer than pine and may crack when dry. The color of spruce is white, with a golden hue.


Sometimes this lumber is called cedar pine. It is a soft rock with a beautiful texture and is easy to work with.

The heartwood of the cedar has a pinkish tinge and its sapwood is white-yellow. In its density, it is similar to pine and spruce.

Cedar is decay resistant, so it will be easy to prevent wood from rotting in the ground. Moreover, it is easy to prevent rot, cracking, and fungi growth during ground contact.

Just like with the previous rot resistant woods, it is very advisable to use it for your fence post, deck, or doors.

How to stop wood rotting outside

Use pressure treated woods

Alkaline copper quat (ACQ) treated woods

ACQ is a water-based wood preservative that repels rot and repels insects.

However, this type of pressure treated lumber can crack, shrink, or warp.

ACQ pressure treated wood has very low to moderate toxicity by inhalation, and skin contact. It can also cause eye irritation. ACQ pressure treated wood is available in brown or green.

It can be in the status of a fence post, flooring, or auxiliary posts. This pressure treated lumber can also be used in childhood for hairpins, beams, and rams.

Just be sure the pressure treated wood doesn’t come into contact with food or animals. For instance, making an aquarium with it is a horrible idea.

Copper naphthenate treated woods

It is a great choice for outdoor work. Copper naphthenate has been classified by the EPA as a general-purpose pesticide. Thus, this pressure treated wood not only prevents decay but also kills termites.

Сopper naphthenate pressure treated lumber is less dangerous for the environment.

The copper naphthenate preservative looks like bright green wood that turns light brown over time. It also has a distinct odor that fades over time.

It is best to use protective equipment such as gloves and goggles when working with copper naphthenate treated wood with its chemical contaminants and odors.

Copper naphthenate treated wood is water resistant and is commonly used for engineering poles, docks, seedling trays, and greenhouses.

How to stop wood rotting outside

How do you keep wood from rotting on the ground?

It is widely considered that the most efficient way to keep wooden fence posts from rotting in the ground is to install them in concrete, rather than applying various oils and chemicals, as they constantly need renewal and won’t give you a 100% protection from rot.

In this guide, we will show you how to install a wooden pole into concrete step-by-step.

Step 1

Before installing a wooden column in a concrete structure, additional protective treatment of the material of natural origin should be performed, as it eventually collapses from aggressive environmental influences.

Step 2

The above-ground part of the concrete column must be treated with a varnish solution, which will weaken the effects of sunlight, precipitation, and weathering.

Step 3

The underground base also needs to be protected from the destructive effects of moisture, microorganisms, and other factors. As a protective solution, bituminous impregnations are most suitable. Processing is carried out in two traces with an interval between works – 24 hours.

Step 4

The main work is preceded by a preparatory stage for preparing the site for installation and digging holes for supports.

Step 5

When the ground is dry, to facilitate digging, water places for wells are moistened. The depth of the pit depends on the height of the fence element – for a pole of 150 cm you should dig the ground by 50 cm, and for a longer fence post – 80 cm in the ground. The underground part of the log should correspond to 30% of its total length.

Step 6

If on the site under construction the level of ground water is high, then to prevent the rot of the tree, the pit is dug to a depth exceeding the ground freezing limit.

Step 7

At the bottom of the well, a gravel dust layer with a thickness of 150-200 mm is laid, it will serve as a drainage system for the concrete base of your fence post and remove excess moisture.

Step 8

The lower part of the wooden post is wrapped with a rolled hydrophobic agent, treated with an open fire, or treated with a bituminous mixture to further protect the concrete ground base of your fence post.

Step 9

Next, wooden support is installed in the hole, it is covered with mixed soil, gravel, and brick breakage. This laying is carefully rammed into the well. A distance of 150–200 mm is left to the ground level; prepared concrete will be poured into this “nest”.

Step 10

After the monolithic solution has matured, the joint between it and the wooden pole is additionally treated with a hydrophobic substance.

This concrete installation will provide the structure of wooden fence posts with strength and comparative durability and prevent wood from rotting in the ground.

How to stop wood rotting outside

How do you seal the wood from rotting?

The ideal option is to turn to professionals. They know in what proportion to dilute treatments, what to give preference to, at what temperature to work, whether it will stay on untreated wood at higher temperatures, as well as other nuances.

But if desired, all procedures can be carried out independently. Just follow the instructions below to prevent wood from rotting in the ground:

  1. All surfaces must be treated are carefully cleaned. They should not leave traces of paint, dust, or fat deposits. Remember, we need dry wood here! They can be scraped off or removed under a strong stream of water.
  2. The next step is sanding or processing with a hard metal brush.
  3. Treatment with a detergent composition for wood, followed by drying.
  4. Careful inspection. If damaged areas are identified, the mold must be scraped off. If the rot has penetrated deep, it is should be cut down with an ax. It is also desirable to eliminate knots.
  5. Then you can apply the selected treatment (more on that below), taking into account the recommendations of the manufacturer.
  6. If necessary, the procedure is repeated after thorough drying of each layer. There should be no unfinished parts left. This is especially true of the ends and seams.

What wood preservative should I buy?

A treatment that we recommend you using is an antiseptic protection from the American company Perma-Chink Systems.

Shell Guard RTU is a wood preservative product against fungal infections and wood parasites, so that you can treat your fence post or deck wood from rotting in the ground.

The effectiveness of the wood preservative is due, firstly, to the presence of boric salts, and secondly, to unprecedentedly deep penetration into the structure of the treated wood. Shell Guard RTU is currently the only wood preservative on the market that can penetrate the thickness of the material to a depth of 15-16 cm.

This is facilitated by the special component contained in the composition of this wood preservative – glycol.

Shell Guard RTU is a colorless and odorless solution that quickly absorbs into the wood (however, exterior finishes can only be applied after at least 12-14 days have passed from the moment of treatment).

But it is especially important that, unlike chlorine-containing wood treatments, the composition does not damage the treated wood fibers, and retains the natural strength and hardness of the treated wood.

To prevent wood from the damage by pests and rot in the ground for the entire service life, it is enough to treat wood with this product once, strictly following the instructions.

Due to its deep penetration, Shell Guard RTU almost completely impregnates each log of wood and does not wash out afterward (of course, with proper care).

How to stop wood rotting outside

What can you put on wood to keep it from rotting outside?

Copper sulfate

It is one of the wood treatments available in the arsenal of any summer resident who monitors his garden.

With the proper use of copper sulfate for many years, you will not have to worry about the appearance of black spots on the pressure treated wood fence posts and raised beds. It penetrates deep into the wood pores, closing them for water and making sure to prevent a fence post, deck, or anything else made of wood from rotting in ground.

But the application is significantly limited by the presence of negative properties. If the wood is constantly or periodically heated, the vitriol will evaporate. Volatile components will be released into the air and may cause poisoning during the drying process. So it is recommended to process outbuildings and external walls.

Work should be done with gloves and goggles, taking reasonable precautions.


Wood tarnishing has long lost its popularity, although it is an environmentally friendly way to prevent wood from rotting in ground. It is enough to wet the logs with water vapor and burn with a blowtorch or gas burner until the wood acquires a uniform brown tint.

It works like this: excess moisture evaporates from the upper layers of wood fence posts and raised beds. The wood structure becomes denser and impervious to moisture. The appearance of mold or fungus on the surface after firing is possible, but wood decay processes are practically excluded.

Aesthetics aside, it will serve its purpose: it will prevent wood from rotting in ground.

Silicate glue

It is possible to give additional strength to wood in basements, and rooms with constant high humidity by applying silicate glue. But the wood must first be well dried.

The composition does not contain components harmful to humans. A significant limitation is an inability to further paint the wood or varnish it. The surface is shiny and smooth.

You can see the drying time of the glue here.

Drying oil with the addition of manganese

Allows you to simultaneously carry out antiseptic treatment and create a moisture barrier on wood. A strong film is formed on the wood surface, which prevents the formation of cracks.

Oak bark concentrate

This drug will prevent the appearance or development of decay on wood for a long time. The only drawback is that light wood will become darker after processing. A 150×150 wood
the house will look different than planned.

A mixture of linseed oil, hemp, and tung oils

Natural oils, such as linseed oil were originally used to protect wooden musical instruments from moisture. After drying, natural oils make a film similar to varnish on the wood surface, since when the components come into contact with oxygen, the polymerization process starts.


This option requires significant costs but is fully justified. Due to the absence of chemical impurities, wax is recommended for use in bedrooms, including children’s, when it comes to protection against wood decay.

How to stop wood rotting outside

How do you fix rotten wood without replacing it?

Rotting wood repair is ideal for areas of wood that are of little structural importance, such as door or window frames. Structural components, such as wood beams and wood pillars, should be replaced if there are signs of dry rot of wood.

There are two ways to repair rotten wood, depending on the size of the damaged area and the state of the rest: use a wood filler, or cut the rotten part and patch it.

Wood filler

  1. Strip away any rot on the rotten wood on your furniture (such as deck or doors) with a wood chisel.
  2. Drill a honeycomb pattern with shallow holes in the wood, using the 3/16-inch (4.57 mm) drill bit. You don’t go all the way through the wood.
  3. Brush the hardener on the wood and leave it for about two hours, or as long as the label says.
  4. Build a shape around the damaged area with hardwood or scrap wood. Create a structure that matches the sides of the damaged area, leaving one side open, and tape it in place with silver tape.
  5. Spray lubricant on the figure before installing it around the damaged area. This way, you ensure that it will come out of the filler when it is time.
  6. Fill the space between the damaged wood and the shapes with filler. Allow to dry for about 10 minutes, or until the filling is solid and rubbery.
  7. Separate the figures and scrape off the excess filling with a cutter. Sand the wood with fine-grit sandpaper to shape and smooth it.
  8. Apply a coat of paint to the wood to seal the patch.

Wooden patch

  1. Cut a block of wood the same thickness, but slightly larger than the rotten stain.
  2. Place the piece on the rotting wood area and mark the outline with a pencil.
  3. Cut out the rotted area along the lines you marked. Use a corner chisel so that the edges fit comfortably into the damaged area.
  4. Apply polyurethane glue to the patch and reinsert it into the damaged area. Hold the wood with the clamp until the glue dries.
  5. Clamps of this type apply pressure to the top and sides of the wood, to ensure that the head is pushed firmly into the clearance.
  6. Sand the entire area that you cleaned for wood rot with fine-grit sandpaper and apply a coat of paint or stain, to seal.

What causes wood rot?

High humidity

The main cause of untreated wood rotting is the high humidity of the air or the material itself. Wet untreated wood is a natural habitat for fungus, mold, and rot. Under their influence, the external qualities of the material, its strength characteristics and other factors will deteriorate.

Wood can become infected with biological agents while still in the forest, they may not show themselves for a long time, but as soon as high humidity, heat, and lack of fresh air kick in, they will begin to act.


Another cause of rotting wood can be insects. They do not worsen the surface layers of the material but make their way into the depths of fence posts and decks.

Many beetles feed on wood fibers, worseming their structure, but the most part is that they can carry a fungal infection that will begin to develop inside the wood.

In this case, the contamination of the material is detected too late, and it is impossible to restore the previous properties of the wood.


Before starting the process of carrying out work whose task is to prevent wood rot, it is important to choose the most suitable composition.

For example, for application to the external surfaces of residential premises, as well as materials stored on the street or the ground, it is better to use specialized highly effective rot-resistant formulations.

But for processing inside the house, it is better to opt for folk remedies that exclude the release of toxins in trees. In general, before processing, it is better to consult with a specialist who will help you choose the most effective and safe means to protect the lumber.

Also, it wouldn’t be a bad idea to use naturally rot resistant wood from the start of your next project to stop the rotting in the ground as well as prevent fungi growth.

Thus, we have given you a wide variety of methods of wood preservation for your next woodworking project!

If you enjoyed this article, feel free to share it with friends if they are as enthusiastic about woodworking as we are!

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