Exterior wood is not one coating job. Decking is horizontal, walked on and slow to shed water; cladding, fences, doors and windows are mainly vertical; garden furniture contains joints, end grain and surfaces that people touch. Choose the treatment from the timber, orientation, old coating, condition, exposure and desired appearance, then build the cleaner, preparation, finish and applicator into one compatible system.
Do not use an interior finish outside
Interior Polyx-Oil, floor lacquer, worktop oil and Door-Oil are not substitutes for a purpose-designed exterior system. Exterior products also have different restrictions for horizontal and vertical surfaces. Follow the current label and product data sheet, test the complete system on the actual timber and obtain specialist advice where the timber, old coating or exposure is uncertain.
Quick exterior wood-treatment selector
| Your project | Main WWFS route | Preparation and applicator | Key limitation |
|---|---|---|---|
| Decking in clear or transparent colour | Osmo Decking Oil | Decking Cleaner for ordinary contamination; Wood Reviver Power-Gel for suitable grey bare timber; apply with the Decking Brush Set. | Clear 007 Teak allows natural greying. Follow timber-specific weathering requirements and do not finish sanding finer than the product guidance. |
| Decking where a neutral Bona penetrating oil is preferred | Bona Decking Oil Neutral 2.5L | Prepare sound bare or previously compatible timber to Bona’s current instructions and use the documented brush or application method. | Do not place it over an unidentified film coating. Confirm colour, absorption and system compatibility first. |
| Clear protection on suitable vertical timber | Osmo UV-Protection Oil 410 or UV-Protection Oil Extra | Apply exceptionally thinly with an Osmo Flat Brush or compatible microfibre roller route. | For vertical timber, not decking. Clear finishes delay greying but do not preserve the original colour indefinitely. |
| Transparent colour on suitable vertical timber | Osmo UV-Protection Oil Tints | Prepare consistently and complete a representative two-coat sample. Apply with a Flat Brush or approved compact roller system. | Transparent, not opaque. Timber colour and grain affect the result. |
| Exterior wooden garden furniture | Osmo Garden Furniture Oil 028 Clear | Apply thinly with an Osmo Flat Brush or lint-free cloth. Revive grey bare timber first where suitable. | Clear and biocide-free with no UV colour protection, so natural greying continues. |
| Suitable bare vertical timber needing preservative treatment | Osmo WR Base Coat 4001, followed by a compatible exterior topcoat | Apply to clean, dry, frost-free suitable bare wood with a Flat Brush or microfibre roller. | It is a preservative base coat, not a decorative or final weathering finish. Read the biocide information before use. |
| Exposed cut ends and end grain | Osmo End Grain Sealing Wax 5735 | Use a small clean brush on prepared ends as part of the complete coating system. | It protects vulnerable end grain but does not replace coating the faces, edges and hidden surfaces. |
| Dirty exterior wood that has not greyed deeply | Osmo Decking Cleaner | Use at the instructed dilution with the Deck Cleaning Scrub Brush; rinse and allow to dry. | A cleaner removes contamination. It does not reverse UV greying or provide final protection. |
| Grey, weathered suitable bare timber | Osmo Wood Reviver Power-Gel | Scrub and rinse as instructed, then let the wood dry before choosing the protective finish. | A reviver is preparation, not a topcoat. An old varnish or paint may need complete removal first. |
Identify the surface before choosing the tin
Horizontal and walked on
Decking faces standing water, dirt, abrasion, algae and repeated wetting. Use a product specifically approved for decking and keep the maintenance cycle realistic.
Vertical or inclined
Cladding, fences, doors, windows, pergolas and summerhouses shed water differently. This is the normal route for Osmo UV-Protection Oils.
Furniture and detailed joinery
Check hardwood extractives, joints, hidden faces, end grain, skin contact and the practicality of brushing or cloth application around profiles.
Unknown old coating
Do not coat through flaking varnish, paint, wax, silicone or an unidentified treatment. Establish whether it must be cleaned, lightly prepared or removed to sound bare timber.
Also identify the timber species if possible. Resin, tannin, oil content, pressure treatment and density affect absorption and may require a weathering or degreasing period. The same oil can look and dry differently on pine, larch, cedar, oak, teak and tropical hardwood.
Cleaner, reviver, preservative and finish are different jobs
| Stage | What it does | WWFS example | What must normally happen next |
|---|---|---|---|
| Routine cleaner | Removes dirt, organic contamination and everyday soiling from suitable untreated or oiled exterior wood | Osmo Decking Cleaner | Rinse or finish as instructed, dry thoroughly, assess whether the protective coat still performs. |
| Wood reviver | Helps remove the weathered grey surface from suitable bare exterior timber | Osmo Wood Reviver Power-Gel | Rinse, let the timber dry fully, lightly de-nib if required, then apply a suitable protective finish. |
| Preservative base coat | Adds preventive protection to suitable bare exterior timber before finishing | Osmo WR Base Coat 4001 | Apply the compatible decorative weather-resistant topcoat after the base has dried. |
| Protective finish | Provides the intended water, dirt, colour or UV performance for the specific orientation | Decking Oil, UV-Protection Oil, Garden Furniture Oil or Bona Decking Oil | Inspect and maintain before exposed timber becomes heavily worn or grey. |
| End-grain treatment | Reduces moisture uptake and splitting risk at vulnerable cut ends | Osmo End Grain Sealing Wax | Complete the finish on all remaining faces and maintain the whole component. |
Decking and other suitable horizontal timber
Osmo Decking Oil
Osmo Decking Oil is the main stocked Osmo route for exterior decking. Osmo specifies two thin coats, or one coloured coat followed by its compatible Anti-Slip Decking Oil where that system is required. Approximate coverage is 24m² per litre for one coat on smooth timber, with around 12 hours drying in suitable ventilation and conditions. Rough, grooved or absorbent wood can use considerably more.
Apply with the Osmo Decking Brush Set. Its 150mm brush follows decking boards efficiently, while the smaller brush deals with edges, grooves and ends. The Osmo Telescopic Handle attaches to compatible brushes and the scrub brush so cleaning and coating can be controlled from a standing position.
New timber may not be ready to oil immediately
Extractive-rich, resinous, pressure-treated and dense tropical timber can need a manufacturer-specified weathering or degreasing period before it will absorb the oil correctly. Osmo currently gives examples ranging from at least four or six weeks to three months according to timber type. Identify the wood and use the current instructions rather than assuming every new board is ready on delivery.
If sanding is required, Osmo’s current Decking Oil guidance recommends a final grade no finer than P120. A surface polished too finely can reduce absorption. Avoid aggressive jet washing, which can raise and damage the fibres and affect subsequent coverage.
Bona Decking Oil
Bona Decking Oil Neutral 2.5L is a professional penetrating oil based on modified vegetable oils for suitable exterior decking and timber. It enhances the grain and helps protect against weather exposure. Choose it when a neutral Bona decking system suits the specification, but do not combine it casually with Osmo cleaners, base coats or maintenance products. Keep each manufacturer’s preparation, application and recoat system intact unless compatibility has been confirmed.
Clear versus coloured decking oil
Osmo 007 Teak is the clear appearance route and lets the timber grey naturally. Transparent pigmented Decking Oils change the colour while leaving the grain visible and generally provide more resistance to visible UV colour change than an unpigmented clear oil. A screen image or colour name cannot predict the result because timber species, weathering, sanding and coat weight all alter it. Test the actual board with the intended number of coats.
Cladding, fencing and vertical exterior timber
For suitable vertical or inclined exterior timber, choose between clear UV-Protection Oil 410, clear UV-Protection Oil Extra, and transparent-coloured UV-Protection Oil Tints. These are not decking oils. Vertical cladding, fencing, shutters, pergolas, balconies, carports and summerhouse timbers have a different exposure pattern and do not carry foot traffic.
Apply two exceptionally thin coats to a correctly prepared surface unless the current product instructions specify another build for the substrate or maintenance condition. Clear and transparent oil systems are microporous and designed for straightforward future maintenance, but they still need inspection and timely recoating.
Osmo UV-Protection Oil 410 versus UV-Protection Oil Extra
| Choice | What it offers | When it makes sense | Important distinction |
|---|---|---|---|
| 410 Clear Satin | Clear, biocide-free exterior UV oil for suitable vertical wood | Where a clear natural appearance is required and a film-protection biocide is not wanted, including appropriate sensitive settings subject to the product instructions | Biocide-free does not mean maintenance-free. It does not include the Extra product’s active film protection. |
| Extra Clear | Clear exterior UV oil with active ingredients that protect the coating against mould, algae and fungal attack | Suitable exposed vertical timber where that additional film protection is appropriate | The active ingredients protect the coating; they do not guarantee that organic growth can never appear. Read and follow all biocide information. |
| UV-Protection Oil Tints | Transparent colour and UV protection while keeping the grain visible | Where a timber-toned, grey, white or darker transparent appearance is wanted | The natural wood colour remains part of the result. Darker transparent pigments generally provide stronger UV resistance. |
Osmo states that its clear UV-Protection Oil system can delay natural greying by a factor of 12 compared with untreated wood under its test basis. Treat that as relative protection, not a promise that exterior wood will never change colour. Exposure, orientation, elevation, overhangs, water traps and maintenance timing all affect real performance.
Clear, transparent colour or opaque?
- Clear: closest to the natural timber appearance, but provides the least pigment screening. Expect colour evolution and plan maintenance.
- Transparent coloured: the grain remains visible while pigment improves colour stability and changes the appearance.
- Opaque: covers more of the timber colour and normally belongs to a different paint or opaque exterior system. The current WWFS stocked selector here is focused on penetrating clear and transparent oils, so ask about the correct specification rather than forcing a UV tint to behave like opaque paint.
Natural, Raw and white-tinted effects require especially thin, even application. Excess white pigment can dry chalky or collect in texture and joints. Always trial the complete number of coats on the prepared timber and view the sample outside in the light where the project will be seen.
Exterior doors and windows
Exterior joinery needs more than a product on the visible face. Coat or protect all accessible faces as required by the system, pay particular attention to bottom edges, glazing details, joints and end grain, and do not leave newly cut or machined timber unprotected. Water entering through an uncoated bottom edge can damage the joinery even when the front face looks sound.
Use the vertical-timber route: 410 Clear, UV-Protection Oil Extra or UV-Protection Oil Tints according to the required appearance and film protection. Osmo Door-Oil is for interior doors, not exterior joinery. Some proprietary door and window manufacturers restrict field-applied coatings or require their own system, so preserve any warranty instructions.
Exterior wooden furniture
Osmo Garden Furniture Oil 028 Clear Satin is designed for suitable hardwood and softwood exterior furniture. Osmo specifies two thin coats, approximately 24m² per litre per coat on smooth timber, and around 12 hours drying in suitable conditions. Apply with an Osmo Flat Brush or lint-free cloth as instructed.
It is biocide-free and water and dirt resistant once dry, but it is a clear finish without UV colour protection. The timber will continue to grey naturally. If maintaining colour matters, ask WWFS to confirm a compatible pigmented exterior route for the species and design rather than adding an unrelated tinted product on top.
Furniture often exposes end grain at legs and joints and may trap water beneath feet or covers. Coating cannot compensate for standing water, poor drainage or storing the item permanently wet. Lift furniture from saturated ground where possible and use breathable protection rather than trapping condensation.
WR Base Coat and End Grain Sealing Wax
Osmo WR Base Coat 4001
Osmo WR Base Coat 4001 is a clear oil-based preservative base for suitable bare vertical exterior timber, especially softwoods. It adds preventive resistance to blue stain, rot and wood-destroying insects and reduces swelling and shrinkage. It is applied by brush or roller and must be followed by a compatible exterior finish after it dries. It is not a decorative topcoat and should not be left as the exposed final surface.
WR Base Coat contains biocidal active ingredients
Use biocides safely. Read the label, product information and safety data before use, observe all restrictions, and do not assume a preservative is appropriate merely because timber is outdoors. Keep it within the specified substrate and finishing system.
Osmo End Grain Sealing Wax 5735
End Grain Sealing Wax protects vulnerable cut ends of decking, cladding, soffits and other suitable exterior timber. End grain can absorb moisture far more quickly than a planed face, increasing swelling, checking and splitting. Apply it to prepared end grain as part of the wider system, particularly after on-site cutting.
It is not a substitute for correctly coating the remainder of the board, dealing with water traps or protecting hidden faces where the construction requires it. Osmo’s external-surface guidance uses WR Base Coat on suitable hidden faces and two thin coats of End Grain Sealing Wax on ends in the relevant system.
Preparation and application
- Identify the wood and coating. Confirm the timber species, whether it is pressure-treated or modified, and whether the old surface is bare, oiled, stained, painted or varnished.
- Repair construction defects. Coating cannot solve rotten timber, loose boards, failed fixings, trapped water, inadequate falls or leaking joinery.
- Check that new wood is ready. Follow the product’s species-specific weathering or degreasing instructions.
- Clean or strip appropriately. Use Decking Cleaner for routine contamination, Wood Reviver for suitable grey bare timber, and completely remove incompatible film coatings where required.
- Let the timber dry. Osmo’s current Decking Oil guidance requires clean, dry, frost-free timber with maximum moisture content of 20%. Do not coat after rain merely because the surface looks dry.
- Sand only as needed. Keep preparation consistent and avoid polishing an absorbent oil surface too finely. Remove dust completely.
- Test the full system. Include preparation, base coat if required, the intended number of finish coats and end-grain treatment.
- Stir thoroughly. Do not thin a ready-to-use finish unless its instructions specifically allow it. Keep pigments evenly distributed.
- Apply thinly along the grain. Use the specified brush, roller or cloth, redistribute heavy areas and clear coating from joints and grooves where it could pool.
- Allow ventilation and full drying. Lower temperature and higher humidity extend drying. Avoid rain, dew, frost and premature use during the stated period.
For applicator selection across all finishes, use Which Wood-Floor Coating Applicator Should I Use?. For exterior decking, the Decking Brush Set remains the most purpose-specific stocked option.
Cleaning, inspection and maintenance
Inspect exterior timber at least seasonally and after severe weather. Look at exposed ends, horizontal ledges, south- and west-facing elevations, door bottoms, furniture feet and areas beneath pots or mats. Clean before dirt and organic growth become embedded, and recoat when signs of wear become visible rather than waiting for widespread greying or cracking.
- Remove loose dirt and leaves before wet cleaning.
- Use Osmo Decking Cleaner for appropriate routine maintenance and the scrub brush for controlled agitation.
- Use Wood Reviver Power-Gel only where the surface is suitable and genuinely weathered grey.
- Allow timber to dry before deciding whether it needs one maintenance coat or fuller preparation.
- Reapply the matching product. Do not alternate brands or chemistries without confirmed compatibility.
- Clean suitable reusable oil tools promptly with Osmo Brush Cleaner & Thinner.
Dispose of oil-soaked materials safely
Oil-soaked cloths and pads can self-heat. Never leave them folded, crumpled or piled together. Follow the product label and safety data for immediate safe handling, storage and disposal, away from heat and combustible materials.
Exterior wood-treatment FAQs
Can I use Osmo UV-Protection Oil on decking?
No. The UV-Protection Oil route is for suitable vertical or inclined exterior timber. Use Osmo Decking Oil or another decking-specific system on horizontal walked-on decking.
What is the difference between 410 and Extra?
410 is the clear biocide-free UV-protection option. Extra includes active film protection against mould, algae and fungal attack. Both are clear vertical-timber finishes, both need correct preparation and maintenance, and neither makes wood permanently colour-stable.
Will clear oil stop wood going grey?
It slows weathering according to the product system, but clear timber still changes outside. Pigmented transparent finishes generally screen UV more effectively. Maintenance timing and exposure remain decisive.
Should I clean or use Wood Reviver?
Use cleaner for dirt and ordinary contamination. Use Wood Reviver Power-Gel on suitable bare timber where the surface itself has weathered grey. If paint or varnish covers the wood, identify and remove the old system as required before expecting a reviver to work.
Can I oil new decking immediately?
Not always. Many species and pressure-treated boards need a defined weathering or degreasing period so extractives reduce and absorption improves. Identify the timber and follow the current coating instructions.
Can I pressure-wash decking before oiling?
Aggressive pressure washing can roughen fibres, damage timber and affect coating coverage. Osmo advises avoiding jet or power washers for Decking Oil preparation. Use the specified cleaner, brush and rinsing method.
Can I use interior Door-Oil on an exterior door?
No. Use a purpose-designed vertical exterior coating and protect faces, edges and end grain as the door manufacturer and coating system require.
What information should I send WWFS?
Send photographs, timber species if known, age, orientation, existing coating, current condition, approximate area, exposure and whether you want clear, transparent colour or an opaque appearance. Contact WWFS before ordering if any part of the existing system is unknown.