Home & Garden Cleaner and Moss killer

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As a professional gardener, I have thrown thousands of pounds of moss killer at mossy driveways, tennis courts, paths and even roofs in an attempt to curb moss growth.

These moss killing chemicals have worked to some degree, however, they have been extortionately expensive and embarrassingly damaging to the environment. Additionally, in my experience very few have been any good at stopping the moss regrowing.

After many hours of research, a gardening colleague came across the use of Sodium Percarbonate as a moss killer. I have written this post to make the information we found more accessible and to help our readers kill moss successfully.

The proper name for oxygen bleach is sodium percarbonate.  Despite its technical-sounding name, it is an environmentally safe product.

Sodium percarbonate is NOT a chlorine bleach, Chlorine bleaches are corrosive and toxic, please try not to use chlorine bleaches in your garden!

How to Kill Moss using Sodium Percarbonate

Moss and Algae attach themselves to surfaces like wood and tarmac by tiny hair-like structures called rhizoids. Sodium percarbonate breaks these rhizoids, effectively cutting off the moss and algae’s support system.

Try not to use a pressure washer to remove moss, this just increases the chance of the moss returning.

One of the greatest benefits of using sodium percarbonate as moss killer is that it is brilliant at killing the spores that allow moss to reproduce, this helps prevent the moss from returning.

2019 has had a particularly wet autumn and moss is going to love it. Tackle it now, before it takes hold and the spores multiply in your driveway.

Buying Sodium Percarbonate.

Sodium percarbonate comes in the form of free flowing tiny granules and is classed as technical grade. It is usually shipped in polyurethane bags or a plastic tub. The label is often generic as the granules have so many uses, it can be sold as deck cleaner, bottle sanitiser or stain remover but it is all the same stuff. Sodium percarbonate is sold by independent suppliers through “>Ebay or Amazon.co.uk.

What’s the Best Way to Kill Moss on Tarmac and Roofs?

The sodium percarbonate granules need water to react and create oxygen. The easiest and most effective way is to spray the area to be treated with water and then sprinkle the granules over the whole area. You will see the granules immediately start to bubble as the oxygen is released and that’s all you have to do!

TIP: If you are sure that a good amount of rain is going to fall within the next few hours, then sprinkle the granules straight onto the moss and let the rain do the rest. This is especially effective if you are treating moss on roofs. I have treated many roofs with sodium percarbonate using this method.

Tackling Weeds on Driveways

If you have a particular problem with weeds, read my post: The Best Way to Kill Weeds on driveways.

Other Uses for Sodium Percarbonate.

Organic matter like algae is broken down by the oxygen which makes sodium percarbonate an effective and inexpensive method for cleaning indoors and out. Some of the best ways to use it are:

  • Cleaning wooden garden furniture
  • Algae killer on patios
  • Kills algae in water features Further Reading
  • Cleaning Decks
  • Lifting Bird muck
  • Killing Moss and Green Algae on and between Block Paving
  • Killing Moss on Tarmac, Drives, Patios and Paths
  • Moss Killer for Tiled and wooden Roofs
  • Sanitising pots
  • Stain remover
  • Kills Moss on Tennis Courts
  • Cleans Artificial surfaces
  • Tile Grout Cleaning
  • Worktops (Except solid wood worktops, as they have usually been treated with Danish oil)
  • Put half a teaspoon in a tea or coffee stained cup and fill with warm water, leave then rinse. The cup will be as clean as the day you bought it.
  • Do not use on pure or untreated wool, silk or leather.

What else can Oxygen Bleach be used for?

We always have a bag of Sodium Percarbonate handy, It can be used together with other detergents and improves their performance. We use a scoop in our laundry, a scoop in our bucket when we mop the floors. It is great for deodorising bins, septic tanks, cleaning dishwashers, washing machines, de-staining tea and coffee cups/pots and general sterilising.

Oxygen Bleach in action.

You can buy Pure Sodium Percarbonate for cleaning tile grout direct from Amazon.co.uk or eBay.co.uk

When spraying,  Sodium Percarbonate needs to be mixed with warm water. This creates a bubbly reaction so if you are using it in a sprayer you need to be careful not to mix up too much at one time. Spray all over and leave for 10 to 15 minutes, you will see the oxygen lifting the dirt, use a brush for very soiled areas and then simply rinse with clean water


  • Sodium Percarbonate can be used with other detergents
  • Use a capful in your washing machine to keep your whites whiter and coloureds brighter!
  • Mix 30 grams with 1 litre of warm water
  • Spread by a gloved hand or scoop, use approximately 50 grams per square metre.
  • Sometimes the mix leaves white mineral deposits on the cleaned area.  This will disappear after rain or an extra rinse, it is not permanent!
  • Always try a small test patch first.
  • One of the advantages of this great natural product is that it does not affect plants or grass as a commercial chemical would. If you over spray near these you have no need to worry!
  1. Hi,
    How much would you mix into a 20litre barrel in order to kill miss on a driveway please?

    • Hi thank you for getting in touch. You can mix 600g in 20 litres of warm water. As an alternative consider spreading the granules by a gloved hand, this method is easier and quicker. We have a very long drive and spread the granules when its raining, alternatively you can damp down the driveway with a hose pipe then spread the granules. If you use this method use, 50 grams per square metre. You will use more sodium percarbonate, but it does ensure the product gets right down into the tarmac killing the moss spores too (important in preventing the moss returning). Please let me know if I can help anymore.

  2. Wow, I cannot believe I found this site. Was looking for a way to kill moss/lichen on my driveway, and wooden fence without hurting the trees and rose bush, and to be able to use in the UK right now with the Winter weather.

    Excellent and excellent.

    Thank you

  3. Hi Last year I cleaned the moss from the concrete tiles on my roof then sprayed them with moss cleaner.

    Not intending to climb up on to the roof again, I purchased a long lance which attaches to a sprayer and should reach all of the roof from ground level.

    I would be obliged if you could advise which quantity of water and sodium percarbonate should be used in the sprayer and can it be applied directly on to the roof during wet or dry weather, also does it require to be hosed of some time after it has been applied


    Allan Jardine

    • Hi Allan
      Thank you for getting touch, you can use 30-40 grams of sodium percarbonate in 1 litre of warm water in a sprayer. You can spray when the roof is wet or dry but I prefer to spray when its wet so the tiles dont soak up the spray too quickly. Do not hose down the roof afterwards, just leave the sodium to do its thing. If I can help further please let me know. I have used this method with a long lance many times and its worked perfectly.

  4. Hi your advise is very much appreciated. The fact that this works on a wet surface has to be a major plus point, as after spraying the roof or block paving with chemical moss remover it usually, in spite of the weather forecast decides to rain, which then dilutes the said chemicals.

    Many thanks

    Allan Jardine

  5. Thanks for the interesting article. If I apply it to my terrace how long do I leave it for and how do I make it safe to walk on for a pet?

    Would also be good to understand what level of coverage you would get for 1kg?

    Thanks very much!

    • Hi Nigel thank you for getting in touch.
      Apply a handful per square metre, in my case, this is approx 40g, this should cover a terrace of approx 20 sqm (4.4m x 4.4m). If you damp down the terrace first and then spread the granules, they will start to bubble. Spread around with a broom if you want to get good coverage. After about 40 mins the granules will have stopped reacting you can then hose off the area and it will be safe for the pets to go on. If you are killing moss on the terrace, e.g. between the joints, leave the sodium for at least an hour, the longer the better. When the area has dried in any case it will have done its job and be safe. Your terrace or deck will carry on looking brighter over the week as the organics die off.

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