Deck oiling: when, how often and how to do it
A wooden deck looks its best when it is well maintained. Left untreated, sun and rain take their toll: the wood turns grey and rough, and may eventually crack. Oiling keeps it nourished, supple and looking good. This practical guide explains why oiling matters, the best time of year to do it, how often your deck needs treatment and how to get it right.
Why should a wooden deck be oiled?
Wood naturally absorbs and releases moisture. Outdoors without protection, three things happen: the sun's UV rays break down the surface and turn it grey; changes in moisture can cause it to warp and crack; and dirt and algae take hold more easily. Oil penetrates the wood and saturates its fibres. It helps preserve the natural colour, reduce cracking and keep water and dirt from settling.
Oiling is preventive maintenance. An annual coat of oil is much easier and cheaper than restoring a deck that has turned grey and rough and started to crumble. If the surface has deteriorated that far, oil alone is no longer enough: it needs sanding first. We explain this below.
When during the year should you oil?
Oil must be applied to dry wood in dry weather, and temperature greatly affects how well the oil penetrates and cures. As a rule of thumb, deck oil is applied at temperatures between approximately 10 and 25 degrees Celsius, and preferably without direct sun on the boards while you work. In practice, this means the season typically runs from May to September.
Spring and early summer are the best times. The wood has dried thoroughly after winter, and you get ahead of the season's wear and algae growth instead of lagging behind. Avoid oiling in scorching sun in the middle of the day, as the oil will then dry too quickly on the surface instead of penetrating. An overcast, dry day is actually ideal.
- Choose a period with dry, mild weather, preferably 10 to 25 degrees Celsius.
- Check the weather forecast: there should be no rain for the first 24 hours after oiling.
- The wood must be completely dry throughout, not just on the surface.
- Preferably oil in the spring to get ahead of the season.
How often should the deck be oiled?
How often your deck needs oil depends mainly on the wood species and its exposure to sun and rain. Softwoods such as pine and spruce absorb and release moisture quickly and need treatment most often. Larch usually needs less frequent treatment than pine or spruce, while dense, naturally oily hardwoods such as ipé and teak can go longer between coats. The more exposed the deck, the shorter the interval.
Recommended oiling interval per wood type
| Wood type | Typical interval | Note |
|---|---|---|
| Pressure-treated pine and spruce | 1 to 2 times a year | Softwood that absorbs and releases moisture quickly; usually treated in spring and, if needed, again in late summer |
| Larch | Approx. once a year | Typically in spring, more frequently on south-facing and very exposed decks |
| Hardwood (ipé, teak, cumaru) | Every 2 to 3 years | Dense and naturally oily; many owners choose to let it develop a grey patina |
The figures are indicative. A south-facing deck without shade wears faster than one that is partly sheltered, and a deck you walk on a lot needs treatment more often. The best guide is the wood itself: drip a little water on a worn spot, and if the water soaks in instead of beading up, it's time for oil again.
Clear or pigmented deck oil?
Deck oil comes in clear and pigmented varieties. The main difference is UV protection. Clear oil preserves the wood's natural appearance but offers little protection from sunlight. Pigmented oil contains colour pigments that protect against UV rays and slow the greying process.
To keep the wood's warm, fresh colour for as long as possible, choose a pigmented oil in a shade close to its natural colour, particularly for exposed, sunny decks. Clear oil is an option if you prefer a natural appearance and are prepared to oil more often. Always use an oil designed for outdoor decking, and avoid mixing product types, as they are not always compatible.
How much oil is needed?
As a guide, allow about 1 litre of oil per 5 to 10 square metres for each treatment. Dry, bare and absorbent wood takes more oil than smooth, previously treated wood, so new or heavily worn decking will use more. Buy a little extra so you can finish without running out halfway across a board, as stopping in the middle of a surface can leave visible overlap marks.
A small leftover amount of oil is not wasted: it can often be used for a quick spot treatment of the most worn areas, for example, near the stairs or in front of the door, where the wood typically wears first.
Step by step: how to oil your deck
- Clean thoroughly. Sweep the deck and wash it clean of dirt, grease, and algae with a deck cleaner and a stiff brush. All grime must be removed, otherwise you'll trap it under the oil.
- Let the wood dry. After washing, the deck must dry completely, at least one day in dry weather, and preferably 2 to 3 days. The wood must be dry throughout; the moisture content should be below approximately 15 to 18 percent before you proceed.
- Sand away roughness (if needed). If washing has left raised wood fibres, splinters or rough patches, lightly sand them with 120 to 150 grit sandpaper. This smooths the surface so the oil spreads evenly and penetrates more effectively.
- Stir the oil. Stir the oil thoroughly to mix the pigment and binder, and stir regularly while applying it. Test a small, inconspicuous area first to see how the colour looks on your wood.
- Apply wet-on-wet. Apply the oil along the grain with a brush, roller or cloth, working on a couple of boards at a time. Keep a wet edge by starting the next board before the previous one dries. This wet-on-wet technique prevents visible overlaps and changes in colour.
- Wipe off excess oil. Let the oil soak in for about 15 to 20 minutes, then wipe away anything that has not been absorbed with a clean, lint-free cloth. Oil left on the surface dries to a sticky, slippery film.
- Allow to cure. Keep the deck dry and free of traffic for the first 24 hours. If the wood is very absorbent, an extra thin coat on the most absorbent boards may be a good idea.
An important safety point at the end: cloths and brushes with oil can spontaneously ignite if crumpled up. Lay them flat to dry outdoors, or place them in water in a closed container before discarding them.
Common mistakes that spoil the result
- Oiling damp or dirty wood. The oil won't penetrate and can trap moisture and dirt. Always clean and dry first.
- Too much oil not wiped off. Excess oil cures to a sticky, slippery film. Always wipe it off.
- Oiling in scorching sun. The oil dries on the surface instead of penetrating. Work in the shade or on an overcast day.
- Visible overlaps. These occur when the edge dries too quickly. Work wet-on-wet on a couple of boards at a time.
- Expecting oil to rescue degraded wood. If the wood is grey, rough and splintered, the weathered surface layer needs sanding before oil can be absorbed properly.
When oil isn't enough: sanding first
Oil works best on sound wood that can absorb it. If the deck is grey, rough and splintered, the weathered surface layer stops the oil penetrating properly. Sanding removes that grey layer to expose fresh, absorbent wood ready for treatment. The deck can then look new again and receive a proper coat of oil.
Thorough sanding is hard and dusty work, and the result heavily depends on the entire surface being sanded evenly so that the oil is absorbed uniformly. If your deck has reached that point, you can read more in our guide to sanding balconies and wooden decks, where we review when sanding is necessary and how to do it correctly. If you want the entire task completed, both sanding and subsequent treatment, you can get a no-obligation quote for balcony and deck sanding. You'll receive a fixed price before we start.
Prefer to leave the work to us?
Oiling is straightforward, but it takes time and needs repeating. It can also be hard on your back and knees, especially on a large deck. Many owners prefer to have it done professionally so the work is carried out properly without having to tackle it themselves each season. This is particularly useful for large decks, wood that has started to turn grey, or when you want the sanding and oiling matched to your wood species.
We advise on the right treatment for your deck and provide a fixed quotation, with a reply within 24 hours. Deck sanding and oiling are not listed as eligible services in the Danish Tax Agency's 2026 deduction guidance, so do not assume that this work qualifies. Read our tax deduction information and find more practical advice in our balcony maintenance guide.
If you want your deck maintained without lifting a brush yourself, we offer an oiling plan, where we come and oil your deck in the right season, year after year. This ensures that the wood is always protected, and you never have to remember it yourself. Feel free to reach out, and we'll have a no-obligation chat about your deck and find the solution that suits you best.
Frequently asked questions
How often should a wooden deck be oiled?
It depends on the wood species. Pressure-treated pine and spruce typically need oiling 1 to 2 times a year, larch about once a year, and hardwoods such as ipé and teak often every 2 to 3 years. The more sun and rain the deck receives, the more often it needs oil.
When is the best time of year to oil the deck?
Oil in dry, mild weather at approximately 10 to 25 degrees Celsius, typically from May to September. Spring and early summer are best because the wood is dry after winter, and you get ahead of the season's wear. Avoid oiling in scorching sun or just before rain.
Clear or pigmented deck oil, which should I choose?
Pigmented oil gives the best protection against UV rays and slows greying. Clear oil preserves the wood's natural appearance but offers less protection and needs applying more often. Pigmented oil is usually the better choice for sunny, exposed decks.
How much oil is needed per square metre?
Allow about 1 litre of oil per 5 to 10 square metres for each treatment. Dry, absorbent wood uses more, so a new or heavily worn deck will need a larger amount. Buy a little extra so you can finish without running out halfway across the surface.
Can you oil a deck that has turned grey?
Not directly if the wood is grey, rough and weathered, as the oil cannot penetrate properly. Sand off the grey surface layer first to expose fresh wood ready for treatment. The deck can then look new again and be ready for oiling.