Osmo WR Base Coat 4001 750ml



Osmo WR Base Coat 4001 is ideal way to provide extra protection to European woods in exterior applications. It penetrates deeply to prevent swelling and shrinkage and gives a water repellent finish to protect againstblue stain, rot and insect attack.

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£18.91 Inc VAT

£15.76 Excl VAT

This works out at: £25.21 per litre
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Not sure how much you need? Try out our Coverage Calculator

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1 coat(s):

1 coat(s):

This figure is only a guide for smooth or planed timber. The coverage can vary significantly depending on the condition of the timber and rough sawn timber will require substially more.






Osmo 4001 WR Base Coat is a clear wood impregnation for exterior use. It is a preventive preservative with active ingredients to protect against plant and animal pests such as blue stain, rot, mildew and insect attack. Nb. 4001 is the replacement for 4005 with the key differences that it is now oil based and contains protection against insect attack as well as biocides. The base coat penetrates easily and deeply into the wood - proving extra moisture protection for the wood. Key features include:

  • Clear (4001), exterior base coat only
  • Especially recommended for windows, cladding, garden furniture
  • Reduces swelling and shrinkage and protects against fungal, algae, blue stain, mould growth & insect attack.
  • Extremely water-repellent, extra moisture protection
  • Ideal primer for Natural Oil WoodstainNatural Oil Woodstain EffectsUV Protection Oil TintsOsmo 410 Clear UV Protection Oil and Osmo 420 Clear UV Protection Oil Extra.
  • Will improve the coverage of the above when used on rough sawn timber
  • Available in 0.125, 0.75 and 2.5 litres
  • 1 litre covers approx 5 - 6 m² with 1 coat. Product coverage will depend significantly on the wood's characteristics. These figures are for smooth planed or cut timber. Other surfaces such as rough sawn, aged timber etc may lead to significantly reduced coverage.

Number of coats:
1 coat, a top coat from the Osmo product range must follow.


Apply by brush, dipping or flooding, spray only in an enclosed unit with appropriate protective equipment.


Approximately 12 hours in normal climatic conditions (23°C & 50% relative humidity). Lower temperatures and/or higher humidity can increase the drying time. Allow good ventialtion when drying.


Up to 5 years or more if the can is kept dry and sealed tightly. Store away from direct sunlight and extremes of temperature.

Please Note:

Osmo WR Base Coat is not a wood finish on its own and requires an Osmo finishing product such as Natural Oil Woodstain, Country Colour or Osmo Decking Oil to be applied within three months. Osmo 4001 WR Base Coat is the replacement for 4005 WR Base Coat Aqua.
It is not recommended for use inside. For internal use or where no biocide and insecticide is required we recommend using Osmo wood Protector 4006, for more details click here.

Area of Use - Exterior only.

Suitable for Doors, Windows & Joinery - Yes

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