Written by Terry Smith

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UK’s best decking cleaner for wooden deck restoration, algae, and black spot removal

This article was last updated on April 23rd, 2022 at 5:54 am

Offering both functionality and practical value, the garden decking area is one of the best places to be in most homes, I know it is in ours – with a pop up gazebo overhead and a wall mounted heater we keep the party going into the night, during the day it’s the sun loungers, charcoal bbq (this can be a problem so use a mat to stop any wood that spits out damaging your deck) area, and soon to be hot tub area all rolled into one – so after the wooden deck gave in, I did a how to build a deck from scratch. I thought going for a recycled plastic look alike deck mean’t I fixed the daily hassles, and I was right to an extent, it still needs blasting off with my cordless pressure washer every so often. It has improved things from my old wooden deck though for sure – I used to need the best deck cleaner money could buy in an attempt to remove Algae, lichen, and a nasty green film that became slippery – basically purge everything!

Deck cleaner can really make a difference

I think my patio is in one of those spots where the sun misses it for a large chunk of the day, and therefore stays damp longer – hence the quick build up. There were no half measures, the strongest deck cleaner I could find, and blasting it with my petrol pressure washer was the only way to clean it properly, and then of course it looked dry and tired so needed – nourishing with decking oil to bring the colour back – you could also use teak oil or Creocote as I do when I clean my shed exterior the same way. It stood up well for about 15 years – considering how quickly Algae and growth built up, I was happy with that but enough was enough, and I swapped over to plastic. If this sounds similar to your story but you’ve not quite decided to make the change, then read on, I have literally a decade of experience using decking cleaners, and subsequently bringing a dry, unhealthy looking deck back to life once cleaned – I’ll show you the best products in the UK – I’m in the South but I’m absolutely confident my knowledge applies up North too, no problem on that 🙂

The best deck cleaner will break down dirt and grime, should remove Algae, help remove black spot and any green slippery bio layer and take a good chunk of the elbow grease out of cleaning. Ideally you find an all rounder but in case you need something stronger biologically, or for stuck in grease we will cover that too. Needless to say my review factors the price and safe to use around the home with kids and pets – so let’s get stuck in and have a looking at the best decking cleaner picks:

Best decking cleaner: editor picks:

Best best decking cleaner in the UK overall: SmartSeal Deck Cleaner
Alternatives picks to SmartSeal: Ronseal DC decking cleaner or CUPRNOL 5083456 Decking Cleaner
Best value for money deck cleaner: Everbuild EVBFUN5 404 Fast Powerful Fungicidal Wash – superb value for money as usual
Strongest deck cleaner in the UK: CUPRNOL 5083456 Decking Cleaner
Large quantity for commercial use: Jarder Spray & Leave
Best deck cleaner that doesn’t need a pressure washer: SmartSeal Deck Cleaner – used with a pressure washer will enhance results though

What you get in this article:

What is decking cleaner and how to pick the best one for your deck?

FAQs when buying decking cleaner

What is decking cleaner and how to pick the best one for your deck?

Deck cleaner, or decking cleaner is pretty similar to patio cleaner that can remove grime and oily stains and works the same way as an algae remover or moss killer does. Some in fact cover all three like the Smartseal Deck Cleaner which is very effective and doesn’t need a pressure washer (though experience tells me from testing you get much better results with a washer):

After using Smartseal Deck Cleaner – huge improvement but a pressure washer can help you go to the next level.

However, there are specific chemical mixes specifically designed for wooden decking which I will be focussing on in this review. Most decking is made from softwood or hardwood. However with that said, I recently made a composite wood decking (recycled plastic) that looked really similar to the real thing, but it’s a safe enough bet you have wood of some kind so let’s stick to that.

Is deck cleaner harmful?

Most deck cleaner is now water based but it’s generally very harmful in to all ponds and children so picking a dry day so it doesn’t run into ponds or rivers is a must. Given the changing rules on health and safety, the formulas have now had to be brought inline with strict regulation. This is a story of two halves though, from an environmental and health perspective it’s much safer, from an actual cleaning perspective it’s much less effective, a bit like the substitute Creocote for Creosote if you’ve ever used a stain on your wood shed 😀

How does deck cleaner work

The idea behind deck cleaner is to remove and kill Algae, penetrating the timber to that point, removing dirt and grease, as well as lifting off any mould and killing that too. This leaves your deck ready to be treated, nourished, or oiled – some even use teak oil over decking oil.

Now here’s where it gets a little more complicated. Some deck cleaners are designed to remove dirt, Algae, and black spot like the quality Smartseal Deck Cleaner whereas the Everbuild EVBFUN5 404 Fast Powerful Fungicidal Wash is more aimed at the biological problem. So when you’re selecting a decking cleaner be sure to know what you’re trying to remove and then check it’s suitable to do so. Most of the negative reviews I see are a case of misunderstanding the ability of the deck cleaner they’ve purchased.

Picking the right deck cleaner for you will come down to how bad your Algae and moss coverage is, how long since the last cleaned the deck, the timber it’s constructed from (normally Red Wood), and how much exposure to sunlight you have. A deck that doesn’t dry out always is the first to get hit with Algae and mould! So for example, if you had all of the problem listed here, I’m probably going to point you toward the Smartseal Deck Cleaner as that is seriously strong stuff but does have it’s pitfalls being so strong!

Fun fact – clean your deck regularly and you’ll get much longer between the times you need to stain and preserve it! Yep, as with all maintenance it reduces the need for a big service and invariably saves you money whilst looking at your pretty deck.

How to actually use the best deck cleaner to make my decking perfectly clean?

Before you get into the main body of work it’s worth doing a little tester with your chosen compound to ensure you’re happy with the result. First off the bat clear an area of any loose debris, and any growth you can remove with a stiff brush or pressure washer is a bonus. Let that area dry out. Now, apply your deck cleaner in an area tucked out the way to make sure it doesn’t react badly to the chemicals you’ve chosen.

Some of the techniques to clean your decking vary. Let’s pick the strongest chemical so you’ll know the most cautious route to take – The Cuprinol decking cleaner. As above clear your area and apply the deck cleaner. Follow the instructions for maximum application time, in the case of CUPRNOL decking cleaner that’s 30 minutes. Make sure you pressure wash off or scrub off your boards before moving onto the next batch. Remember, don’t let the deck cleaner spill onto boards already cleaned or it’ll fade them further until your new stain or wood oil brings the decking back to life. Here’s a cracking little ten minute video you can skip through to show you what can be done!

Talking of which, once you’ve pressure washed off the area its now time to let your decking dry. At this point you want to seal in with lacquer or stain your decking as soon as possible to stop dirt getting into the grain of the wood directly again.

Since I last reviewed the best deck cleaners, there’s a new sheriff in town – to dethrone Ronseal DC decking cleaner or CUPRNOL takes some doing by the way. SmartSeal Deck Cleaner is one of the best commercial products and arguably better than my favourite CUPRNOL when compared for strength and ability to clear decking without a pressure washer. They make all sorts of brilliant block paving and patio sealers with some of the best reviews in the UK for their products. If you compare costs they are pretty similar in that this will treat 40m2 and the Cuprinol about 15m2. So the costs then workout to be pretty similar, unless you buy the bulk offer of this product then it makes it considerably better value for money. Better still, lesser affected areas can probably be diluted by half extending the amount of coverage further still.

You’ll really like the application process – simply spray it on, give it a good brush into the surface with a nice stiff broom and leave it for an hour but crucially make sure it’s still damp, this will stop bleaching or damage to your decking. I’d use this when I need a seriously solution – you’ll remove black spot with a couple of applications. You’ll have to trouble bringing decking back to as new condition. You’ve seen the picture above of what can be done without a pressure washer, add one into the equation and you’ve got a serious deck cleaner and worthy of the best pick in the UK currently.

There’s another added positive too. I’ve notice where I keep jetting off my decking it’s started to go a little grainy and torn looking in places – assuming you udon’t use one as I mentioned, you’re decking will definitely thank you for it.. This is definitely as a result of the pressure washer nozzle being too close and having too much pressure but all the same, worth pointing out.


  • Sensible price for such a quality product
  • Simply brush in and clean off after an hour
  • 40m2 of coverage
  • Genuinely kills Algae and mould fast


  • Only lifts organic matter not oil and grease stains

Next up, the next most reliable name in wood restoration and preservatives – Ronseal. They literally do everything, from shed preserver, wood stain, right through to two part polyester based wood filler. A trusted name, and a trusted product, if anything despite my opinion, this has a better reputation online than CUPRNOL! The fast acting formula of the Ronseal DC decking cleaner removes dirt, fungi, algae, mildew, stains and grease from the wooden surfaces pretty well. It’s definitely an all rounder for soft and hardwood decking.

When I reviewed this a couple of years ago there hasn’t been any change to the formula of note. The Ronseals formula isn’t far off Cuprinol when compared. The active anti-fungal ingredient Benzisothiazolone is present in this product and acts as the wood preserver. Similarly to Cuprinol you’l get about 5m2 per litre as well. I’d definitely suggest using Ronseal Quick Drying Wood Stain in combination if you decide to go with this deck cleaner.

Again I’d go down the apply neat and pressure washer route myself. Be careful though, bleaching your boards is quite possible though when that happened to mine the wood oil brought them up beautifully again.


  • Great on wooden decking
  • Excellent value
  • Really works to lift grease and Algae
  • Anti fungal wood preserver for long lasting protection


  • Need to be careful when applying as you can fade your boards (only temporary until stain applied though)
  • Like Cuprinol some issues with not working for some.

Let me give you a little background on Cuprinol. I have been using their preservatives for literally decades and are absolutely on point. Cuprinol 5 Star is probably one of the best treatments of my lifetime, let alone best now. My good friend Brian Turner at London Sash Window Repairs Ltd literally swears by Cuprinol 5 Star and he’s one of the leading respected wood restoration specialists in the country

The decking cleaner formula, though not the same as 5 star, does its specific job brilliantly. So brilliantly in fact, that you ought to concentrate on cleaning up a couple of boards at a time. I made the mistake in the past of applying this NEAT with a garden sprayer, with the intention of then blasting it off with my beastly petrol pressure washer. I totally ignored the recommended process and my boards actually faded. I sprayed it twice and left it on for a couple of hours thinking I’d really clean it up. Well I did that alright. It didn’t just strip off the Algae and mould with the dirt, it actually chewed into the timber and bleached the boards as well! Also it’s worth mentioning this formula has a It also has a sterilising effect that prevents the regrowth of these. Hence the way it bites into your boards, treating the timber beneath surface level (I told you Cuprinol was the best). This isn’t some sales tactic that looks great on paper, Cuprinol have been treating timber for 75 years!

On the downside though I noted a few reviews online suggesting this DOES NOT work. Have to say, they must have randomly had bad batches, my problem was total opposite, I can only assume over dilution or something or a bad batch? Neat this stuff really is strong, no question.

So two things to take from that then, one, it’s a highly effective product and worth every penny, two, it’s the best decking cleaner in the UK for strength (oh, and follow the instructions? :D)

Talking of following the recommendations, forget what the pack says :D, realistically you’ll get about 5-7m2 of coverage per litre if your decking is knackered and in need of a damn good clean. That’s a pretty safe bet from the two times I cleaned up my decking with Cuprinol in the last couple of years using this formula. Don’t be cheap, the job this will do for you warrants the investment, buy two bottles if it’s tight, and you can thank me for that boot in the behind later 😀

There’s two ways to do this, if you don’t have a petrol pressure washer to follow the method I mentioned above (or a powerful electric pressure washer for that matter, then it’s back to good old elbow grease. You want a reasonably stiff wire brush that isn’t too course. Apply the treatment and give it ten minutes then scrub away. Get your hosepipe (by the way you might want to take a look at wall mounted automatic garden hose reels, a total game changer!) and give it a rinse off. Wait for it to dry so you can see how it’s come out. You might want to repeat the process, if not you’re ready for decking stain and deck treatment.

Let’s be honest, the only reason you don’t buy this deck cleaner is because the Ronseal, gives far more cleaning coverage per pound.


  • Super strong deck cleaner
  • Best decking cleaner in UK
  • Anti fungal so acts as a wood preserver too
  • 75 years treatment research and development


  • Need to be careful when applying as you can fade your boards (only temporary until stain applied though)
  • Some have had a bad experience
  • Double price of Ronseal nearly.

The Everbuild EVBFUN5 404 Fast Powerful Fungicidal Wash is not strictly a decking cleaner, it’s an all round multi purpose anti fungal cleaner that doesn’t damage wood so makes it totally suitable for this application. It’s also suitable for use as a block paving and patio cleaner. If you’re not familiar with Everbuild yet then it’s worth knowing they produce extremely good quality products, my favourite being their Everbuild patio sealer. They are trusted and respected for their treatments and preservatives UK wide.

So with so many decking cleaners to review why have I picked an all rounder this time? Well, the answer is simple, this is considerably cheaper than Ronseal and far cheaper than Curprinol when we compare like for like coverage. You can reasonably expect to get as much as 50m2 out of one 5 litre bottle. Given it’s cheaper still and far more coverage, it makes it an absolute steal and definitely the best value for money deck cleaner in the UK.

Before I go on though, it’s worth mentioning that your fish won’t thank you if this ends up in the pond nor your kids. So I’d be looking to use this on a dry day.

For the best possible results you’ll want a pressure washer but scrubbing hard works fine too. Simply dilute it down a bit if you like and spray it on with a pressure sprayer. A cautionary word that you may change the colour of your timber temporarily until you stain or oil it again. The result is normally something near new.


  • Great all rounder that works well for wood and composite decking
  • Excellent value – best in the UK
  • Specifically aims at killing Algae and mould then protecting.
  • Huge coverage


  • Not as strong as Cuprinol
  • Needs leaving on longer than manufacturer recommends in my opinion.

Jarder Spray & Leave is designed for patio, fencing, and decking. In short, pretty much any surface that’ll pick up Algae and mould growth – however it’s more of a fungal killer on decking than cleaner so take note. The reason I’ve picked this all rounder is to kill two birds with one stone. First off the bat they sell it 20 litres at a time for very sensible money if you need serious volume. Secondly, if you need a couple of the Everbuild, or even three bottles, this is essentially one free and stores in the shed for ages – no harm at all with the child proof lids…and being multi purpose you’ll certainly find a use for it.

When you compare it to the Everbuild you won’t have any issues at all with the quality. Both are up to the job of killing and loosening Algae and mould, taking a fair bit of the strain out of the process. I’ll say it again though, with volume it’s probably even more important – you could do with a jet washer to lighten the load.

The application varies when compared to conventional deck cleaner. This is a spray and leave product. What’s interesting is the idea to just leave it is fine but doesn’t actually clean the decking. So your best bet is pick a dry day, then spray it on with a garden pressure sprayer. Leave it be and then get your pressure washer and blast it off once the formula has killed the Algae and mould. So if you’re into a less elbow grease method of cleaning up the decking and don’t mind waiting then this is a pretty decent product for you.

Something worth thinking about is the possibility that heavy thick cover may need a second treatment further delaying the process – personally I’d blast off what I can first if it’s really bad when using this product.


  • Excellent value for money on bulk purchase
  • Spray and leave rather than clean
  • 240m2 of coverage


  • Takes a few days to work
  • More of a fungal killer than cleaner

Jeyes 4-in-1 Patio and Decking Power definitely deserved including in the list. With coverage up to 180m2 making it by far the best value deck cleaner on our list. However with those staggering figures it’s easy to realise that there’s no where near the potency on Ronseal for example that can only cover a max of 40m2 with 5 litres when compared directly by volume.

There’s a few important things to consider when using Jeyes. Firstly removing any excess growth first will accentuate the results. Then apply with a garden sprayer and in contrast to other deck cleaners, leave this to dry out. The fact that this is the manufacturer guidelines should tell you just how little active ingredient is in the product compared to the top pick decking cleaners For example when compared to Smartseal or Cuprinol it is vital to remove quickly to avoid any damage to your deck.

Personally I would buy this if I had patios, block paving, and decking to clean at the same time and I wanted to save money. Where it isn’t specifically specialising in decking or anti fungal properties it struggles to keep up with specific specialist decking cleaners.


  • Incredible value
  • Has multiple uses
  • 180m2 of coverage
  • Kills Algae and mould


  • Not as good as specialist deck cleaners
  • Takes a while to dry and do its job

The Buysmart Products 2.5L Green Gone Decking is another one of the organic matter killers and not designed to remove oil. So as long as you know what you’re buying you can either use this as intended or in combination with a grease removal agent after. Something simple like washing up liquid should help you get the grease and oil up after.

In terms of value for money buying three of these seriously reduces costs. To the point this becomes excellent value for money deck cleaner for removing organic material. You can get about 375m2 of deck cleaned for similar money to the cost of one smart seal when you compare them for coverage by the same costs. It’s actually even better value than the Jeyes and so makes it doubly attractive given its much more powerful at removing Algae and Mould.

The way you use this deck cleaner is the same as the Jarder Spray & Leave. Simply spray it one with a garden sprayer and leave it to do its work. However, give consideration again to the fact this is very nasty stuff and you should only be spraying it when the family and pets aren’t around. It’s no longer active when dry so fine after that. Some leave it a few days and then scrub / pressure wash off their decking. The results are normally pretty good if you give it time. You can expect your decking to be a clean faded brown once the process is complete. Now is the time to treat your decking with a stain or similar. I love wood oil myself to give it a shiny gloss look but that choice is up to you.


  • Incredible value
  • 175m2 of coverage
  • Kills Algae and mould very well.


  • Not the strongest
  • Takes a while to kill Algae

FAQs for buying decking cleaner

Who would have thought deck cleaner could be so complicated. Who much to dilute? What does it kill? Will it lift oil? Do I brush it on? How do I clean it off? How long do I apply it for before washing off? Does it work with a pressure washer? There are actually a fair few variables as you can see from the quick questions I just fired off above. So the key is to do a fair bit of research first and make the time to read this review thoroughly so you know what you’re getting yourself into and what is the best deck cleaner for you.

How much deck cleaner should I use?

Picking how much to dilute your chosen deck cleaner by is down to how severe the Algae and mould on your decking. If you have decking in poor condition you may chose not to dilute at all and will possibly need to repeat the process. Much of this though is down to how much growth you can remove with a stiff broom prior to application of your decking solution.

What will my deck cleaner remove?

Interestingly some deck cleaners are specifically an anti-fungal and do not remove dirt or grease like the Buysmart Products 2.5L Green Gone Decking. This is a common misconception. If you’re looking for an all round solution then you ned to go for the Cuprinol decking cleaner or Ronseal deck cleaner options. You can of course use a combination of these but if you’re looking for good value for money the best way to handle this is a Fungicide and then use washing up liquid and a scrubber to pull up any stuck in dirt and grease. Then of course pull out the pressure washer to finish the job if you have one.

Is there any pet friendly deck cleaner?

Most deck cleaners become inactive once dried much like pet friendly weed killers. The best thing you can do is check the manufacturers guidelines to be sure. Remember before most have dried that are extremely harmful and should be handled and use with care.

About Terry Smith

I’m Terry Smith from gardentoolbox.co.uk, a professional landscape designer, hobbyist gardener, and barbecue fanatic with 20 years experience building and restoring. So as you go through my site you'll watch me document some of the professional garden installs I make as well as the major projects I take on at home. While sharing those experiences and guiding you, I'll be recommending some great tools I use to enable this along the way so you can really buy in confidence. Always feel free to pop me a message: info@gardentoolbox.co.uk

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