Should you sand or oil your wooden deck?

We get the question every week when the season starts: can the deck make do with a layer of oil, or does it need to be machine-sanded first? Fair question. Sanding takes longer and costs more, so most people hope for oil. But if you choose oil for a deck that actually needs sanding, you'll pay for a result that won't last the season. This guide is solely about the choice: what the two treatments can do, what signs determine the matter, and what it costs to guess incorrectly.

Two treatments, two completely different tasks

Oiling is maintenance. The oil penetrates the outermost layer of the wood, revitalizes the colour, and creates a protective film against water, UV, and wear. But oil can only add something - it doesn't repair damage already present in the wood. Deeply greyed, scratched, or cracked wood won't look good with new oil. You'll just seal the problems under a fresh film.

Sanding is renewal. The machine removes the outermost, degraded layer - all that grey, dirty, and rough material - exposing the fresh wood underneath. The deck is reset, and the subsequent oiling can actually last.

Hence the rule of thumb: if the deck needs maintenance, oil is sufficient. If it needs renewal, it must be sanded first. If you skip sanding, the oil is just a layer on top of the problem.

Choose oil if the deck looks like this

Look for these four things. If you can check all of them, you're in maintenance territory:

• The surface is smooth and even. No deep scratches, no loose fibres, no areas where the wood is raised.
• The colour is faded, but uniform. The wood looks dry and dull, but the coating isn't blackish-grey or stained in a way that's stuck in the fibres.
• The old oil is adhering well. If it just looks dull without cracking or flaking, new oil can be applied over it.
• Water still beads. Pour a little water on the planks. If it beads, the surface has enough protection that oiling can build upon what's there.

If this is the picture, you can confidently skip the machine this year. We've compiled the work itself in a separate guide on oiling a deck.

Choose sanding if you see even one of these signs

Here, it's the other way around: a single sign is enough to indicate that oil alone won't solve anything.

• Deep greying or patchy discolouration. The silver-grey patina isn't harmful in itself, but it means the top cell layer has been degraded by sun and rain. Oil on grey wood covers unevenly and lasts only briefly because the degraded layer absorbs differently.
• Rough surface with raised fibres and splinters. Typically after moisture has penetrated and frozen, or a treatment that has flaked off. If you oil over it, the surface will be ugly and uneven, and the fibres will rise again.
• Cracked or flaking old treatment. The flakes form a barrier that new oil cannot penetrate. It will just lie on top and come off again.
• Soft, dark areas and black spots deep in the wood. Soft or decaying wood needs assessment before any surface treatment. Sanding cannot restore structural strength; damaged boards may need replacement.
• A previous DIY treatment with the wrong product. Too thick oil, paint, or a product that didn't suit the wood type. This kind of film cannot be over-oiled - it must be sanded off before you can start fresh.

Common to all five: something is blocking the oil or has already broken down, and no surface treatment can salvage it. You can read about how the work itself is done in our guide on when sanding is necessary.

The five-minute check

In doubt? Do three things before you decide:

• Pour water on it. If it beads, there's protection to build upon. If the planks immediately absorb it, the treatment is used up.
• Run your hand over the planks. Smooth and even suggests oil. Fibers, splinters, and rough areas suggest sanding.
• Look at the old oil. If it adheres well and just looks dull, you can build upon it. If it's cracked or flaking, it needs to be sanded off first.

What does it cost to choose incorrectly?

Oiling a deck that should be sanded seems like a saving, but it rarely is. The oil lasts a shorter time than it otherwise would, because it lies on top of degraded wood or an old film. The next time the deck needs treatment, the problems are still there - often a little bigger. In practice, many end up paying for the sanding anyway, just later and on a deck that is more worn than it needed to be.

The error the other way around is manageable: if you sand a deck that could have made do with oil, you've spent more than necessary, but you have a durable result. So, the most expensive mistake is to guess in favor of oil.

Still in doubt? Describe the deck to us

Some decks are in a grey area: uniformly greyed, but with a few rough patches or some suspicious dark spots. Here, assessing the wood type, condition, and old treatment is half the work. This is how we ourselves start every job with professional balcony and deck sanding: inspection first, then sanding in one or two stages, and finally the agreed-upon after-treatment.

Call us at 20 98 88 11 and describe what you see. We'll then honestly tell you if you can get by with oil, or if sanding is necessary first, and you'll get a fixed price before we start. We'll get back to you within 24 hours.

Frequently asked questions

Can you oil over old oil?

Yes, if the old oil adheres well and is neither cracked nor flaked. If the surface is also clean and smooth, new oil can build upon the old. Flakes, cracks, or an excessively thick old layer, however, mean sanding - new oil cannot penetrate and will not last.

Does oiling help with scratches in the wooden deck?

Only partially. Superficial scratches can be concealed by good oiling to some extent, but deep scratches that have penetrated the wood itself are not smoothed out by oil. They will only disappear with sanding, which removes the layer in which the scratches are located.

Can a deck be too degraded to be sanded?

It rarely happens. Even very worn decks can usually be sanded, as long as rot and fungi haven't deeply penetrated the wood's core. If individual planks have rotted through, they are replaced and the rest are sanded.

How often should a deck be sanded if it is oiled continuously?

With proper oiling once or twice a year, most decks last eight to twelve years between sandings. The better you maintain the oiling, the longer you can postpone the next sanding.