Trykimpraegneret Brun Varbergparken 02

Pressure-impregnated wood

Frøslev is Denmark's largest producer of pressure-impregnated wood produced according to the Nordic Wood Preservation Council’s standards. Impregnation prolongs the natural durability of the wood, makes it very hardy and protects it from dry-rot, fungal and insect attack, making impregnated wood suitable for most outdoor construction projects.

Why you should choose pressure-impregnated wood

  • Impregnated all the way to the core of the wood
  • Protected from dry-rot, fungus and insect attacks
  • Green- or brown-impregnated
  • Suitable for most outdoor projects
  • Produced according to Nordic Wood Preservation Council’s (NTR) standards
  • 20-year durability warranty on selected products


All pressure-impregnated wood from Frøslev is either FSC- or PEFC-certified. Read more about the certifications here.


Most associate pressure-impregnated wood with a greenish colour. The colour comes from the copper in the impregnating liquid and will eventually disappear.

Today, copper and fungicides are used for impregnation in Denmark where the copper content is between 0.1-0.2% of the weight of the wood. Copper compounds only trigger a classification as hazardous waste in terms of health hazards when the concentration is higher than either 20% or 25%. Danish impregnated wood is thus not classified as hazardous waste according to the Danish Environmental Protection Agency.


It is also possible to pressure-impregnate wood to make it brown rather than green. The wood undergoes the same protective process. The only difference is that brown pigment is added to the impregnation liquid which is deposited in the wood surface and masks the green colour.

Brown-impregnated wood has the same durability as traditional pressure-impregnated wood but has a warm, golden colour. Please note that the brown colour may vary.

Patination and maintenance

The colour patinates over time

Neither green- nor brown-impregnated wood can be considered surface-treated or painted, and the colour will therefore eventually patinate and become greyer.

Especially the brown colour will gradually fade due to UV exposure from the sun. If the treated wood is fully exposed to the sun, for example on a terrace without cover, the wood may fade quite quickly.


Use maintenance to extend the life of the wood

Wood is a living material that is affected by the elements. However, continuous surface treatment will extend the life of the wood and make it last for many years.

If the brown shade in brown-impregnated wood is requested preserved, continuous care is necessary with wood preservatives for coloured wood.

Adjusted boards (sawn, processed or otherwise) must also receive a finishing treatment with a suitable primer on cut surfaces, e.g. GORI Transparent Primer 11.

How we produce pressure-impregnated wood

Frøslev impregnates according to the Nordic Wood Preservation Council's standards, and you will therefore find the NTR symbol on our wood. That is your guarantee that the wood is impregnated with a product approved in the Nordic countries.

During pressure impregnation, wood preservatives are pressed into the wood under pressure. The wood preservatives contain active substances against dry-rot, fungi and insects. This makes the wood much more resistant to biodegradation and therefore prolongs its life.

Pressure impregnation results in deep and full penetration of the protective agents into the sapwood, the most porous part of the wood. The sapwood is saturated with impregnation liquid and is therefore protected against biological organisms. Heartwood is not normally penetrated through impregnation as the structure and density of the heartwood and the content of resin and heartwood substances do not allow penetration of the impregnating agents.

Impregnated wood may not be used in wood-burning stoves or bonfires but must be disposed of under proper conditions. Follow your municipality’s instructions regarding waste management.



The wood is placed in specially developed steel tank


All air is sucked out of the tank


The tank is filled with the impregnation liquid


Under high pressure, the impregnating liquid is pressed into the wood


Excess liquid is pumped out and stored for later use


After drying, the wood is fixed for 48 hours so that it dries properly. It is a requirement from the Danish Environmental Protection Agency and only applies to Danish pressure-impregnated wood


We only use water-proofing agents for which a risk assessment has been carried out and which have been approved by the Danish Environmental Protection Agency. This provides a guarantee for durability as well as environment. Danish Impregnation Control and our internal control guarantee the quality of our process and products.