How to Use Osmo Oils & Anti-Slip Treatments on Decking

Published : 19/08/2021 10:28:46
Categories : Our Blog

With the UK currently in the heart of summer, you’ve most likely already washed off the grill and sent invites to barbecues that will almost inevitably get rained out. But, persevering as we are, we’ll get a brolly out and all will be right with the world. Well, all except your decking, because moss + water = a very slippery surface that’s always one wrong step away from giving you or your guests a nasty fall. If you’ve fallen victim, or just narrowly avoided, the moment your heart skips a beat because your foot gives out or you’ve slipped and slid around, then you’re probably wondering how to make decking anti slip. Let’s start by taking a look at why outdoor timber treatment is important.

Why use anti slip?

Because rain is such a significant part of UK weather all year round, anti-slip treatment for wooden decking is a vital part of exterior wood treatment. It’s not only the best treatment for new decking because it reduces the risk of accidents in cold and wet weather, but decking oil or stain actually also increases the durability of the wood by protecting it against mould, algae and fungal attacks. In addition to being a great exterior wood preservative and a safety measure, it also goes a long way in enhancing the look of your decking. An oil-based deck stain like Osmo Decking Oils or Osmo Natural Oil Woodstain are two great options if you’re after a natural look, as both are transparent and will retain the appearance of the natural grain of the wood used. Please note that it’s very important to use a product with a coloured pigment if you want reasonable UV protection on a horizontal surface like decking.

The Osmo 430 Anti-Slip Decking Oil is another clear option, but this one is designed to act in one of two ways; 1) a top coat over one of the above mentioned products, or 2) a maintenance coat once the initial application has started to weather. What’s especially great about the Osmo 430 is the fine granular content that enhances the anti-slip properties of the decking. Not only that, but it also contains a biocide to discourage the growth of moss, lichen, and algae, all contributing factors to slippery decking in winter. Osmo finishes are also microporous so they do not need to be sanded back before applying a maintenance coat, just clean the area with Osmo decking cleaner, and allow it to dry before applying a thin maintenance coat. The Osmo Anti Slip Decking Oil should typically be applied annually, depending on its position and level of exposure.

It’s also worth noting that anti slip paint and decking varnish exists, but might not always be the best anti slip decking solution for you. Not only are they both prone to cracking, flaking and/or peeling over time but they will also require sanding back to bare wood when it's time to re-apply. Only use it on a surface where you expect a lot of foot traffic, such as a restaurant, as sanding back grooved decking will require specialist equipment. 

Where to use anti slip:

We’ve spoken a lot about anti slip in treating home decking, but it also goes a long way in wooden walkways and steps both in- and outdoors. In reality, it's a fantastic product to use on any timber exposed to the elements as it remains the best way to protect exterior wood in a cost effective way whilst also adding grip. Two birds with one stone, really, and who doesn’t like saving time, effort and money? 

Anti slip is also a great product for commercial properties like pubs, restaurants, cafes and clubs. In most cases, rain isn’t the only thing wetting your deck. Add drink spillages, mopping and upturned water bowls in some cases (hello dog friendly establishments) to the equation and you’ve got a lot of factors contributing to a slippery deck or wooden walkway. Investing minimal time and cost in outdoor wood treatment can go a long way in avoiding injury and securing repeat custom. Besides, it’ll be an easy box to tick for insurance purposes, too. 


As with most DIY wood projects, there are a couple of things to keep in mind in terms of suitability, but anti slip, for the most part, is within anyone's reach. 

Most standard softwood decking bought in the UK comes pressure treated, which is the process of forcing chemical preservatives into the wood to help protect it against rot and decay. Therefore, to allow the staining caused by the pressure treatment to fade, and to allow the wood to try out, pressure treated decking needs to be left to weather for 12 weeks before applying any Osmo decking products. Osmo recommends that with Pine, Spruce, Larch, Accoya and Kebony the wood is treated with Osmo 4001 WR Basecoat prior to the main application. With exotic and extractive rich timbers such as Cedar, Iroko, Teak, Ipe, Balau the wood is left to weather for 12 weeks before application so the high oil content in the wood doesn’t prevent the Osmo from being absorbed and adhering. This process can be sped up by wiping the surface of the decking with a clean cloth dampened with Methylated spirits and turned regularly as the cloth becomes dirty. For more information on what is required for different timbers please see the Osmo UK information page on the product.

Similarly, Osmo products must only ever be applied to bare wood as it won’t sit on top of painted, varnished or non microporous coated decking. So when applying a microporous decking treatment such as Osmo Natural Oil Woodstain or Decking Oil, it’s important to strip or sand it fully before applying any treatment. It’s also worth noting that Osmo Anti-Slip Decking Oil only functions as a top coat and should always be preceded by a single coat of Osmo Wood & Decking Oil or the Osmo Natural Oil Woodstain. If you are unsure, always carry out a test first. For overly weathered or grey surfaces, consider using Osmo Wood Reviver to restore your wood to its former glory before sealing it. 

Choosing What Colour to use for Your Decking:

Osmo offers two different products suitable for treating decking. The first are the Osmo Decking Oils that are hard wearing and, with the exception of the clear 007 teak oil, contain a high level of pigments that’s great for good UV protection (generally the darker the colour the better the UV protection). It is important to note that the images used by Osmo show the decking oils applied to matching timber so it’s most likely not the same colour you will achieve when applying it to standard softwood decking. That’s why we always recommend testing on a small area first with the 5ml Osmo oils test sachets. Below is a guide of how oils will appear when applied to softwood decking as two coats or as a single coat of decking oil covered with a single coat of anti slip decking oil.

004 Douglas Fir

UV Resistance ⭐⭐⭐⭐ (With 2 Coats)

006 Bangkirai

UV Resistance ⭐⭐⭐⭐ (With 2 Coats)

007 Teak Oil

Clear Product with No UV Resistance

009 Larch

UV Resistance ⭐⭐⭐⭐ (With 2 Coats)

010 Thermowood

UV Resistance ⭐⭐⭐⭐⭐ (With 2 Coats)

013 Garapa

UV Resistance ⭐⭐⭐⭐ (With 2 Coats)

014 Massaranduba

UV Resistance ⭐⭐⭐⭐ (With 2 Coats)

016 Bangkirai Dark

UV Resistance ⭐⭐⭐⭐⭐ (With 2 Coats)

019 Grey

UV Resistance ⭐⭐⭐⭐ (With 2 Coats)

020 Black

UV Resistance ⭐⭐⭐⭐⭐ (With 2 Coats)

Image Not available

021 Bog Oak

UV Resistance ⭐⭐⭐⭐⭐ (With 2 Coats)

Please note that images on a screen are only ever an approximate guide, the final colour will depend on the wood, application, age etc so a test application should always be done first.

Osmo Natural Oil Woodstain is a penetrative wood stain with an active ingredient designed to resist algae, mould, mildew and fungal attack, and can be applied as two coats, or, for better wear resistance, it’s recommended you apply a single coat followed by a single coat of Osmo anti slip decking oil. This woodstain doesn’t have the same high levels of pigment as the decking oil does, so this product will generally require more regular maintenance than the decking oil.

How to treat decking with anti slip:

Regardless of which product you settle on, here are a couple of steps in preparing your decking for its anti slip treatment. 

  • Always start out by testing an inconspicuous area to ensure you’re happy with the result and that the wood and product are a good match.

  • When you’re ready, make sure the deck is clean. Sweep all dust and debris away and use Osmo decking cleaner to clean the surface. Although jet washing looks like an easy method it will damage the surface of the wood and significantly reduce the coverage of the oil. Grey and silvered areas should be treated with Osmo Wood Reviver.

  • Following a good wash, the deck must be left to dry properly. 

  • Fill out any cracks with a product like Osmo Woodfiller .

  • When using the Osmo 430 Anti-Slip Decking Oil, always treat your decking with a pigmented coat of Osmo Decking or Natural Oil Woodstain first.

  • Ensure it dries properly - it could take up to 10 - 12 hours.

  • If your decking is already painted or varnished, you’ll have to start out by stripping or sanding it. Make sure everything is properly removed before preparing the wood for treatment by following the steps above (always check the instructions on the tin).


Now that you’ve gone through the trouble of creating a safer, anti slip decking, you probably want to keep it that way. Fortunately, with the Osmo products specifically, it’s a piece of cake. To avoid a lot of work, just make sure to regularly clean the decking with Osmo decking cleaner and apply a maintenance coat, instead of waiting until it is in a bad state of repair.

And that’s our guide on how to use Osmo products to create long lasting and anti slip decking. Achieved with minimal cost and effort, it’s a great way to make problem areas safer whilst also showing your outdoor (or indoor in some cases) products some love. With an anti slip decking you can finally enjoy your outdoor area all year long and greatly improve the safety of walking across your decking throughout the year.