How To Get Rid Of Moss On Concrete
How To Get Rid Of Moss On Concrete
Moss is a common, low-growing plant that prefers damp, shaded conditions and can spread easily if left untreated. Moss growth on concrete can be a problem for UK homeowners as it can thrive on areas such as driveways, patios and walkways. At first it may seem harmless, but it can create slippery surfaces, damage the concrete surface and harbour bacteria. With the right approach, it can be appropriately treated before further development. In this guide we will talk you through several different methods for removing moss on concrete and how to prevent regrowth.
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Why should you remove moss on concrete?
There are numerous reasons why you should remove moss from concrete surfaces, both practical and for safety precautions.
- Slippery surfaces - moss, especially when wet, can create a slip risk hazard. If left untreated it can easily spread across your patios or driveways, increasing the risk of slips and falls.
- Surface damage - the moss build-up can cause cracks, erosion and deterioration of the area.
- Appearance - as moss can be unsightly, it can make your home look dirty or unkempt if left.
- Hygiene - wet moss can be the perfect environment to harbour algae, fungi and bacteria. It is best to remove it to help keep the concrete dry and avoid harmful microorganisms.
- Maintenance - as it spreads so quickly, unless ‘permanent’ precautions are taken, it can be time-consuming to maintain and clear.
Tools and materials needed
When cleaning moss off concrete, you will need a variety of different tools and materials depending upon your preferred method. Please see the list below for all items needed for all cleaning techniques.
- Stiff brush or broom
- Garden hose
- Bucket
- Pressure washer & pressure washer detergent
- Washing up liquid, white vinegar, bleach or moss remover
- Rubber gloves
- Eye protection - (such as safety glasses or goggles)
- Protective clothing
Methods of removing moss
Before you begin removing the moss, it’s important that the area is ready. Start by clearing any leaves, dirt and debris from the surface area with your broom or stiff brush.
Next, you need to ensure you are wearing suitable clothing for the job. These could include wearing rubber gloves, eye protection, suitable footwear & overalls (if applicable).
Washing up liquid & water
This simple mixture is a popular homemade moss killer for concrete. It is used for light moss growth and is the mildest option for removal. Warm water mixed with washing up liquid helps to loosen the moss and makes the scrubbing more effective. It is also safe for plants, pets and children, and widely available as a convenient solution.
Fill a bucket with warm water and add your washing up liquid to it - only a few squeezes of the bottle are needed. Pour the soapy water directly onto the area, and let it sit for 15 minutes. After this time, use a stiff brush to scrub the concrete, and then rinse thoroughly using your garden hose (or clean water in the bucket). This may need to be repeated a few times for the best results.
Boiling water
You can simply use boiling water as a chemical-free alternative for removing moss from concrete. As high temperature kills moss, you just need to pour slowly over the affected area to loosen and remove from the surface. Once the moss has turned brown or softened, you can scrub with your brush and rinse clean. This method may require repeat application, as heat alone may not reach all root structures. When following this technique, also ensure precautions are taken to prevent any burns and avoid splashing.
White vinegar
This method is typically used for more stubborn areas. The acidity of the white vinegar helps to kill the moss and makes it easier to scrub away. Apply carefully (avoiding contact with skin and nearby plants), directly to the moss and leave for 15-30 minutes. During this time, the vinegar should loosen the moss and make it easier to scrub/sweep away. For very thick moss, leave the vinegar for up to an hour to improve results - reapply if needed. After the moss has been removed use your garden hose to neutralise any remaining vinegar and residue.
Baking soda
Baking soda is a gentle option for moss removal. It works by drying it out and disrupting its growth. All you need to do is sprinkle directly onto the area (or mix with water to create a liquid solution), and leave it to sit for 24 hours. Usually after this time the moss loosens and can be scrubbed away. As this is a mild solution, you may need to repeat the process for best results.
Diluted bleach
Using diluted bleach is an effective way of removing moss from concrete. Mixing one part household bleach with four parts water in a bucket, creates a strong solution for heavy moss removal. Ensure necessary PPE is worn and appropriate precautions are taken whilst using. Never mix with other cleaning solutions as this can create dangerous fumes.
Pour or spray directly onto the area (avoiding any nearby plants) and let it sit for 10-20 minutes. During this time, the moss should loosen and may turn a lighter colour as it dies. After the area has been treated use a stiff brush or broom to remove the dead moss and reapply if necessary. After using, ensure you rinse the concrete thoroughly to remove any residue.
It is to be noted that repeated use of this method can gradually weaken the concrete over time. For this reason, diluted bleach is best suited for occasional use only, alongside other preventative measures.
Commercial moss removers
Using a commercial moss remover (or patio cleaner) is normally recommended for heavy moss removal. Before use, make sure you read the manufacturer's instructions as application method, safety precautions and removal times can vary depending on the product used. Usually the product will come in a spray bottle making application easy, whilst others you may need to dilute before use. Spray directly onto the moss and let this sit for the amount of time stated on the label. After the waiting period, you can use a stiff brush or broom to scrub the remaining moss away. Again, ensure all residue is removed appropriately by rinsing with a garden hose afterwards (and avoid all nearby plants).
Pressure washer
Using a pressure washer is an effective way of removing moss from concrete. You do need to take precaution that you are using a pressure washer that can be used for this kind of removal and that the appropriate nozzle is used (usually a wide-angle spray nozzle is recommended). There are a variety of different detergents available, so ensure you purchase the correct one that is suitable for your moss removal (and that won’t damage the area).
Lightly wet the area with clean water before starting, but avoid soaking the area completely. Hold the pressure washer nozzle about 20-30cm away from the surface before spraying, and use sweeping motions to wash the moss away. Start in smaller sections and repeat if necessary. It’s important to avoid very high pressure as it can damage the concrete, so make sure the nozzle is appropriately directed and avoid spraying in one area for too long.
This method only eradicates visible moss growth as it does not kill all spores, so you will need to combine this method with other treatments or persistent use. Check out our pressure washer guide for more in depth detail.
Common mistakes to avoid
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Using the wrong solution - if you only need to treat light moss, using harmful chemicals can be damaging. Ensure you are taking the appropriate steps for the severity of the growth. Milder solutions can be just as effective as commercial removers.
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Safety precautions - PPE is an essential part of removing moss from your garden or driveway. Ensure you are kitted out with the appropriate clothing before starting the job. Also make sure you read the label on any hazardous chemicals you are using before application.
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Using too much pressure - when using a pressure washer, make sure you are using the correcting settings to avoid damaging your concrete surface, or nearby plants/wildlife.
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Surrounding areas - when using harsh chemicals, ensure you protect the nearby area and check for any wildlife that might be present.
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Weather - ensure you choose a dry day before treating the moss. Rain can dilute the solution you’re using which may mean it’s not as effective.
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Incomplete removal - once your solution has been applied to the area, ensure you scrub away once the moss has weakened to guarantee complete removal. Equally, wash away (with clean water) any residue afterwards for best results.
How to prevent moss from returning
Preventing moss regrowth is mostly about making the environment less favourable for it to grow. As it thrives in damp, moist conditions ensuring adequate sunlight can help long-term prevention. Also keeping the area clean, by regularly sweeping and removing any leaves, dirt and debris from the area will help. If longer-term protection is required, you can apply a concrete sealer which makes it harder for moss to grow by reducing water absorption.
Key considerations
When removing moss from concrete, there are some key things to consider before taking on this project. Firstly, you need to ensure that the area you are treating is suitable for the solution you have chosen - if the concrete is porous; using hazardous chemicals or high-pressure (pressure washer) can weaken and damage the structure of the concrete.
You also need to ensure that long-term preventative measures are being taken to avoid having to repeatedly do this. This can include things like keeping making sure your concrete is dry by improving drainage in the area.
Getting rid of moss on concrete is not just a cosmetic choice, and should be adequately dealt with to prevent regrowth. Check out our how to clean patio slabs guide for further tips on outdoor cleaning.