Osmo WR Base Coat Aqua 4008 Clear Exterior Wood Preservative

Osmo WR Base Coat Aqua 4008

Osmo WR Base Coat Aqua 4008 is a clear, water-based preservative base coat for the preventive protection of exterior timber. It penetrates the wood and helps protect it against wood-discolouring and wood-destroying fungi.

It is suitable for dimensionally stable, limited dimensionally stable and non-dimensionally stable exterior timber, provided the wood is not in direct contact with soil or water. Typical applications include windows, exterior doors, shutters, cladding, pergolas, fencing, garden buildings, carports and other above-ground timber structures.

Important: WR Base Coat Aqua 4008 is an impregnating base treatment only. It is not a complete final finish and does not provide full protection against sunlight and weathering. A suitable exterior top coat must therefore be applied after drying.

Benefits of Osmo WR Base Coat Aqua 4008

• Clear water-based preservative base coat

• Preventive protection for exterior timber

• Effective against wood-discolouring fungi

• Effective against wood-destroying fungi

• Suitable for a wide range of exterior timber structures

• For wood without direct soil or water contact

• Ready to use and must not be diluted

• Suitable for brush or roller application

• Low odour during application

• Odourless after drying

• Tools can be cleaned immediately with soap and water

• Suitable for private and professional use

Suitable applications

Osmo WR Base Coat Aqua 4008 can be used on:

• Window frames and exterior doors

• Shutters

• Timber cladding

• Pergolas and covered structures

• Fences and privacy screens

• Garden buildings and carports

• Wooden garden furniture

• Posts, beams and other above-ground timber structures

Do not use on wood that will remain in direct contact with soil, surface water or other water.

Surface preparation

The timber must be clean, dry, absorbent and frost-free. Its moisture content should not exceed approximately 20%.

Completely remove old paints, varnishes and other closed-film coatings. Thoroughly clean existing microporous surfaces and remove dust, dirt, loose fibres, grease and other contamination.

Protect plants, ponds and adjoining surfaces before application. Stir the product thoroughly. WR Base Coat Aqua 4008 is supplied ready to use and must not be thinned.

Always perform a trial application when there is any uncertainty about the substrate.

Applying WR Base Coat Aqua 4008

Apply the preservative generously and evenly with a suitable brush or application roller. Where possible, treat all sides of the timber and pay particular attention to cut ends, joints, edges and other vulnerable areas.

For consistent absorption, use our recommended brushes and rollers shown among the related products below. An unsuitable or poor-quality roller may distribute the product unevenly.

Work carefully in the direction of the wood grain and avoid puddles or local accumulations. Clean all application tools immediately after use with soap and water.

Apply at an air and surface temperature between 10 and 30°C and at a relative humidity below 80%.

Application rate

The required application rate depends on the intended preventive protection:

• Approximately 100 ml per m² against wood-discolouring fungi

• Approximately 150–160 ml per m² against wood-destroying fungi

This equals approximately 6–10 m² per litre, depending on the intended use, timber species, absorbency and surface structure. Rough, weathered or highly absorbent timber may require more product.

Drying time

Allow approximately 24 hours to dry under normal conditions at 20–23°C, 50–65% relative humidity and with good ventilation.

Lower temperatures, higher humidity and insufficient ventilation can significantly extend the drying time. Do not apply the final coating until the base treatment is completely dry.

A final coating is always required

Osmo WR Base Coat Aqua 4008 is not a complete standalone finish. Once dry, the treated timber must be finished with a suitable Osmo exterior coating.

Uncovered timber must receive its final coating within three months. Select a suitable exterior wood stain, opaque exterior coating, decking oil or UV-protective finish according to the timber species and intended application.

Without a top coat, weather exposure may wash the preservative from the timber. The chosen final finish provides the required colour, weather resistance and UV protection.

Safe use

Use wood preservatives safely. Always read the label, safety information and official product instructions before use.

• Keep out of reach of children

• Avoid contact with food and animal feed

• Do not allow the product to enter soil, ponds, drains or surface water

• Protect plants and adjoining surfaces from splashes

• Absorb spillages immediately

• Dispose of contents and packaging according to local regulations

• Store in the tightly closed original container

• Protect from frost and temperatures above 30°C

Download the safety data sheet for Osmo WR Base Coat Aqua 4008