What Is Wood Preservation? [Explained Easily]

What is wood preservation?

For wood and wood products to last, they must be well preserved. But how? What is wood preservation? And why does it concern you?

Wood preservation involves the use of chemicals to prevent or slow down decay or damage in wood. In other words, when you buy chemicals to treat or prevent decay or damage to your furniture at home, you are preserving it. The chemicals stop the decay that is often caused by fungi or insects.

Preserving your wood products, such as furniture and wardrobes, has huge benefits. For example, it prevents decay and increases the lifespan of the wood.
In this article, we talked about why you need to take good care of your wooden products and ways you can do it! So make sure to read till the end of the article to discover it all.

Importance Of Wood Preservation

When we preserve wood, we protect it against fungi and insects that may destroy it completely. Preserving wood has lots of benefits and economic importance. We have listed them below.

  • Wood decomposes very fast in hot and humid tropical weather. But this process can be slowed down or prevented using wood preservatives
  • Wood preservation plays a vital role in conserving trees in forest areas. Wood preservation reduces the demand for replacing wood in these areas thus conserving the forests.
  • For countries such as India that are big importers of wood, a longer wood life through preservation helps conserve foreign exchange. This way countries depend less on foreign goods, which helps to boost their domestic currency or exchange rate.
  • The demand for new wood (domestic and imported), including the replacement of wood, has grown considerably. Yet, this negatively affects forest conservation. Both can be prevented if the wood is properly treated and adequately protected with the use of preservative chemicals.
  • Preserving wood helps prevent dry rot. Dry rot is a wood-destroying fungus that digests the parts of the wood which give the wood strength and stiffness. Dry rot can destroy any wooden structure inside or outside your home. As a result, the affected wood must be removed and treated immediately.
  • Wood preservation prevents wet rot. Wet rot is a more common form of timber decay caused by fungal growth induced by damp conditions. Wet rot is common in woods that have high moisture content. Not only does it cause decay in timbers but also carpets and wallpaper.

Methods Of Applying Wood Preservatives

There are various methods of applying preservatives to wood. But there are two main methods: pressure and non-pressure methods.

We have explained both methods below:

Pressure Treatment

When applying preservatives to wood using pressure, the wood is placed in an air-tight steel cylinder and dipped into a preservative. Increasing the pressure of the cylinder drives the preservative into the wood.

There are two ways to do this:

1. Full Process

This process ensures that the wood retains as much preservative as possible. First, a preliminary vacuum is used to remove as much air from the wood as possible. This is done so that the wood can absorb more liquid preservatives.

The heated preservative enters the cylinder without adding air. Next, pressure is applied to the cylinder until the desired amount of preservative is retained by the wood.

2. Empty Cell Process

Unlike the full process, the empty cell process ensures that the preservative penetrates deeper into the treated wood. But retention is relatively low. To begin with, the wood in the cylinder is subjected to air under pressure. Next, the preservative is forced into the cylinder, and as this happens, air escapes into an equalizer tank at a rate that keeps the tank’s pressure constant. After filling the cylinder with preservative, more pressure is applied to it until the desired amount of preservative has entered the wood.

Sometimes wood can rot or damage even after applying preservatives. Usually, this could be because the wood could not retain enough preservative or the preservative didn’t penetrate deeply enough. The effectiveness of wood preservatives depends largely on penetration and retention. How deep down the preservative will go depends on the type of tree, the proportion of the sapwood to the heartwood, and the kind of treatment process used.

Non-Pressure Treatments

Non-pressure treatments may include brushing, spraying, pouring and dipping, cold-soaking, hot and cold bath, diffusion and vacuum process. Unlike pressure treatments, these do not provide maximum protection against wood decay. But it’s okay to use them where less protection is required or where pressure treatment is unnecessary.
We have explained how non-pressure treatments are done below.

Brushing, Pouring & Spraying

This is often done on cut or machined surfaces of woods that have been treated before. Here, the preservative doesn’t penetrate deep into the wood. A popular material used for this procedure is creosote. It is a thick black tar that is generally heated before it is applied to the wood.

Before applying creosote or other oil-made materials to wood, these chemicals should be warmed enough so that they can penetrate deeper and easier. In addition, make sure to allow the liquid to cover the entire wood surface, including depressions in the wood before allowing it dry. You can repeat this process if you want. But wood treated with this procedure can only be between 1 to 5 years.

Other Methods Of Applying Wood Preservatives


This is when you immerse wood in a preservative. This process can last from a few seconds to several minutes. Although dipping allows better of wood preservatives, it is not full proof against wood decay. It offers little protection against termites and is not recommended for wood used in contact with the floor.

Cold Soaking

This process gives more protection than dipping. Wood is immersed in a vat containing a low viscosity oil preservative for 2 to 7 days. Cold soaking is simple to do and relatively inexpensive. In addition, you can steep freshly cut or seasoned wood for several days in a tank full of water-made preservatives.

Double Diffusion Process

In this process, freshly cut timber or seasoned wood is dipped first in a water-made preservative before it is immersed into another (different) one. This process allows the two preservatives to form a reaction in the wood when they combine. The double diffusion process is known to be highly resistant to leaching.

Thermal Process Treatment

This treatment involves immersing the wood alternately in separate tanks containing heated and cold preservatives, which could be oil or water-made.
A single tank can be used if there are not enough tanks available. At this point, the tank is first heated then allowed to cool.

When the wood is dipped in the heated tank, air inside the wood expands and some are forced out. As heating continues, the preservative penetrates more.
When immersed in a cold tank, the air in the wood contracts, creating a little vacuum as the tank’s pressure forces more preservatives into the wood.

Preservative Pads

These pads are used to add an extra layer of protection to wood that is nearing the end of its protection time. An example is light poles. In this method, the soil around the wood is scraped off and the preservative is applied to the surface of the surrounding soil. Another approach is injecting the wood with the preservative or placing it in drilled holes in the wood. After this, the treated areas are wrapped with heavy-duty and water-resistant pads or bandages, to keep the application together.



Joe Taylor

Over 2 decades of remodeling experience, Joe is an expert in home improvement. He is now the Managing Editor of PlumbJoe where he writes guides for homeowners. His hobbies include climbing, running and playing the piano.

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