Preasure Treated Timber

Pressure Impregnated Wood

1. What does pressure-treated timber in a pressure kiln mean?

Pressure-treated kiln-dried timber is wood that, through the application of preservatives, is protected for many years against fungi and insects. To achieve this result, the wood is placed inside a sealed horizontal cylinder, after which the air is extracted both from the cylinder and from the cells of the wood. The preservative is then introduced, and the contents of the treatment cylinder are subjected to pressure. In this way, the preservative penetrates deeply into the wood cells. Afterwards, a vacuum is applied again to ensure that any excess preservative is completely removed. The process is completed with a fixation treatment to ensure that the preservative remains permanently within the wood.

2. Why should wood be pressure-treated?

Wood is a renewable and natural material that is continuously available thanks to the sustainable management of forests. However, it is vulnerable to attacks from fungi, microorganisms, and insects. In particular, when in contact with soil and water, wood is quickly affected and, over time, usually decays. Fungal attacks can also develop rapidly in other environments where wood is exposed. There are only a few types of wood that are naturally highly resistant to decay and insect infestation. These are mostly tropical hardwoods and are very expensive. Other types of wood must therefore be protected before being used in permanent constructions for long periods of time. By pressure-treating wood, its lifespan becomes many times longer than that of untreated wood, while the additional cost of treatment is relatively low, especially when compared with the high maintenance and replacement costs associated with untreated timber.

3. How durable is wood naturally?

The natural durability of wood depends largely on the type of wood, its density, the age of the tree from which it is cut, and the conditions under which the wood is used. These factors are always variable, but wood impregnation provides the assurance of long-term use across a wide range of applications. Untreated wood is never stable.

4. How is timber impregnated with preservatives?

The impregnation industry uses advanced techniques in which the timber to be treated is impregnated through vacuum-pressure cycles in order to achieve the required absorption and depth of penetration.

5. What happens after the impregnation process is completed?

After the impregnation process is completed, the wood remains in the cylinder until the preservatives have been fixed.

6. Can all types of wood be preserved through impregnation?

No. Due to the biological differences between wood species, there are differences in the degree to which preservatives can penetrate the wood. For example, preservatives penetrate only a few millimeters into spruce, whereas the sapwood of pine is permeable all the way to the core. In this case, untreated sapwood becomes vulnerable to fungal attack.

7. Effectiveness of a wood preservative

To be effective, a wood preservative must provide the following properties:

• toxicity against organisms that destroy wood

• the ability to penetrate deeply into the wood

• permanence in the treated wood

• it must not have destructive effects on the wood itself

• it should be non-corrosive to metals

• it must not be harmful to human health

All European countries have regulations and reliable procedures for evaluating the above-mentioned properties. Approval is not granted for impregnation preservatives used in certified wood treatment plants until all relevant examinations by the competent authorities have been satisfactorily completed. The European Biocidal Products Directive provides a unified approval system throughout the European Union.

8. Is treated timber safe for the environment?

Yes. Timber that has been treated in accordance with regulations and with officially approved preservatives does not pose a risk to humans, animals, or plants. Researchers, as well as government authorities, continuously investigate methods and practices related to treated wood products. Research covers every aspect, including the waste-disposal stage. All these studies repeatedly confirm that treated wood is safe for both people and the environment.

9. Where can treated wood be used?

Treated wood is used for:

• electricity and telephone poles

• railway sleepers, crossings, and bridge timber

• industrial cooling towers

• marine docks and piers

• embankments

• vineyard stakes and fencing

• playground equipment, gazebos, and pergolas

• decorative applications (wooden planters)

• sidewalks and walkways

• structural timber

In addition to the above, treated wood is also used for any application where it is exposed to outdoor weather conditions.

10. Can children safely play in playgrounds where the equipment is made from treated wood?

Several studies have concluded that there is no danger to children playing on playground equipment made from treated wood. There is no risk from the leaching of the preservative treatment, even if the wood is licked.

11. Is treated wood safe for use in vegetable gardens, potagers and ornamental gardens?

Yes. Treated wood is ideal for low garden border fences, fencing, pergolas and gazebos, planters, trellises and panels, decking and enclosures, compost bin constructions, as well as vineyard or garden stakes for plants such as beans, etc. There is no risk of damage to plants from the wood treatment components.

12. Is pressure-treated timber safe for people?

Provided that the timber is properly treated (in accordance with European regulations), pressure-treated wood does not pose risks to human health. For every purchase of treated timber, the consumer has the right to request a timber treatment certificate.

13. Should pressure-treated timber be painted after construction?

No, this is not necessary, since the wood has already been treated through to its core. However, there is also the aesthetic aspect to consider. After some time, untreated pressure-treated timber changes color (developing a grayish shade) due to exposure to outdoor weather conditions. The speed at which this happens depends on the location where the wood is used. Our company recommends tinted or clear wood stains that penetrate the wood, are odorless, and environmentally friendly. The only requirement is that the wood must be dry before painting or staining.

INDUSTRIAL CYLINDER IMPREGNATION PROCESS

14. Impregnation using the vacuum–pressure–vacuum process

1. The timber is placed inside the impregnation cylinder and subjected to an initial air vacuum. Air is removed from the wood pores, and the vacuum is maintained.2. While under vacuum, the cylinder is filled with wood preservative.

3. Hydraulic pressure is applied, forcing the preservative to penetrate deeply into the pores of the wood.

4. The final vacuum stage removes the preservative that was not absorbed by the wood, and this preservative is returned to storage.

5. The wood remains inside the cylinder under air pressure so that the preservative is absorbed into the core of the wood.

6. The treated timber is left to dry under atmospheric conditions.