What is pressure treated timber?

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What is pressure treated timber?

The term pressure-treated timber is all over our website and is heavily featured in the world of fencing. However, it is not often addressed what this actually means. This blog post will go through the definition of timber itself and go into more detail about what it means to be treated.

Firstly, timber is classified as wood which is used for building houses, furniture, fences, etc. The other part of the definition is that you can use timber to speak about trees which are specifically grown to be used in building or construction. Whilst timber is a word which is all over the internet, the definition is often not present and therefore can lead to confusion.

Secondly, pressure-treated timber is often briefly mentioned but often not expanded on. Saying that timber is treated sounds great but what does it mean? Pressure-treated timber is wood which has been subjected to chemicals to try and increase its lifespan. It should also be noted that tanalised timber is the same as pressure-treated timber, tanalised just refers to the most commonly used chemical which is Tanalith.

The two main types of pressure-treated timber are UC3 and UC4.

UC3 – The wood is placed in a large tank or container which is then sealed to create a vacuum. Once there is a vacuum the chemicals are then pumped into the tank. The vacuum forces the chemicals into the wood, to a depth of a few millimetres.

UC4 – The process of UC4 is identical to UC3 treatment apart from the preparation of the wood. The timber is first kiln-dried so that the moisture content is only 28%. This allows the chemicals to penetrate the wood deeper and therefore increase the lifespan of the wood.

There is one more piece of help related to pressure treated timber, you may see the term pressure treated green given as the colour for some products. The green aspect comes from the fact that the chemicals contain copper which reacts with the oxygen in the air and can cause a slight green tinge in areas. However, if a product is described as pressure treated green it will still have a natural wood colour and won’t actually be green. The degree of green will vary from product to product but it will never be the primary colour so you can buy your treated timber boards or pressure treated green fence panels with peace of mind.

As a final point, having timber which has been properly treated is essential. The reason behind it is that you must remember that your fence is exposed to the elements 365 days a year and it needs all the protection it can get. If wood is left without protection, then the wind and rain will break it down at a much faster rate than if it was treated. The addition of more timber treatments or paints once the fence has been constructed will help increase the natural lifespan of the wood further, but they are not essential.

We hope this blog post was helpful and that you have all the information you might need to construct your fence. If you have further questions or need any more advice, don’t hesitate to get in touch at info@fencingessentials.co.uk or call us on 01980 669900.