Osmo UV-Protection-Oil Extra on sun-bleached garden furniture: a review

Our garden furniture is an Ikea NÄMMARÖ six seater, a table and six chairs, bought a few years ago and left out every summer since. By this spring it had gone silvery grey and fibrous, and oddly light and dry to pick up, as if the timber had lost whatever was holding it together. A few slats had cracked and the glue joints were letting go. The bog standard furniture protector we'd been using never seemed to last a season, so this year I went looking for something better and ended up with a tin of Osmo UV-Protection-Oil Extra. It's brilliant. Here's a chair after the first proper rain we've had in weeks.

Does grey garden furniture need a wood hardener, or just oil?

What I had in my head was a tin of jollop that would soak right in, bond the tired fibres back together and make it waterproof again, and the first thing I learnt is that no such tin exists. A wood preserver is a biocide wash that fights rot and adds no strength. A wood hardener, or a penetrating epoxy like Smith's CPES, is for timber that has actually gone soft. A UV oil is what stops sound wood going grey again.

Which one you need seems to come down to a fingernail. If you can press a nail in and the wood gives, it wants a hardener first. Ours didn't give - grey and dry on the surface, solid underneath - and from what I've read that's the usual case, because UV damage is mostly a surface thing. So it became a clean, sand and oil job. If yours is worse and you do use epoxy, bear in mind that oil won't soak into cured epoxy, so keep it to the soft patches and sand anything shiny back to matt.

How much prep does it need?

Not much, in our case. The broken slats got exterior wood glue and a dowel where the split ran through, then I scrubbed the set down, let it dry, and gave it a quick going over with a sanding block - enough to take the loose grey fibres off and get back to wood with some colour in it.

The weather did more of the work than I did. It has been an extraordinarily dry summer, even up here in Cumbria, and the rain only really arrived in August, so by early July the furniture had been baking for weeks. I wasn't sure whether you could apply the oil to damp wood and I never had to find out.

What is it like to apply?

The tin I bought was the 1420 Clear Matt, the matt version of the 420 clear satin, and the Extra in the name means it has a biocide against mould and algae as well as the UV filters. It goes on thin - Osmo are quite insistent about that on the tin, and anything left sitting on the surface stays tacky for ages, so brush it on sparingly and wipe off what hasn't soaked in. It wants 12 hours between coats, which meant a coat each evening over two days.

I bought it from Amazon for £28.99 - here's the link: Osmo UV-Protection-Oil Extra 1420 Clear Matt, 750ml.

Two coats on the table and all six chairs used most of the tin, with a bit left for touching up. The finish is properly matt, with none of the plasticky sheen of a varnish, and the colour came back from grey to a warm honey brown as soon as the first coat went on, more of a transformation than I expected from a clear product. The wood feels heavier and no longer dry to the touch, though whether that's the oil or the sanding I couldn't tell you. After six weeks of sun and then a week of rain there's no sign of it greying off.

Is Osmo UV-Protection-Oil worth the money?

At £28.99 for 750ml it's roughly twice what the likes of Cuprinol charge for a garden furniture stain, and it stings enough on the shelf that I nearly didn't buy it. The coverage is what won me round: Osmo quote around 18 m² per litre per coat, so a tin is good for about 13 m², and one tin did our set twice with change. A yearly top-up will use a fraction of that, so per application it's no dearer than the cheap stuff that didn't work.

The one thing I'd think harder about with hindsight is the colour. The clear does have UV filters in it, but Osmo say the pigmented shades in the same range protect for longer. Ours sits in full sun, of the Cumbrian variety, and the clear has been fine so far, but if yours gets the proper stuff all day one of the light tints is probably the safer bet.

How long will it last?

Six weeks is not long enough to say, and a finish like this only really proves itself in its second year. Osmo's guidance is a maintenance coat when the surface starts to look dry, roughly annually for furniture left out all year, and the appeal of an oil over a varnish is that the top-up is a wipe-down and a thin coat rather than a strip back. I'll update this next spring with how it has come through a Cumbrian winter.

The Amazon link is an affiliate link. If you buy through it I get a small commission and you pay the same price. I bought the tin myself and nobody asked me to write this.