How to remove black spots from patio in five simple steps

Rid your patio of mould and mildew with our essential guide

Patio with painted wooden benches and fire pit
(Image credit: Future PLC)

Black spots on the patio are unfortunately a common issue that many of us will have to deal with at some point or another. And if you've recently spotted the unmistakable signs of mould and mildew settling into your paving stones, you're probably wondering how to remove black spots from the patio, and fast. 

Black spots appear when mould and algae have settled into the pores of the paving stones, but before you reach for one of the best patio cleaners on the market and get stuck into how to clean a patio, it's worth considering how to avoid the issue occurring in the first place, and it can help to have a good drainage system in place.

'Whether your patio is made up of natural stones or patio slabs, they will inevitably show some form of biological growth over the winter and spring months, such as algae and mould,' says Jonathan Kirby, Garden Expert, Roxil. 'But you can follow a few simple steps to tackle black spots.'

So if black spots have started to appear on your patio, they don't have to be a permanent fixture. We've asked the experts how to remove black spots from patio, so you can get back to enjoying your patio ideas without distraction.

Two tone grey patio area with table and chairs

(Image credit: Brett Landscaping)

How to remove black spots from patio

Our guide will tell you how to remove black spots from the patio in five simple steps. First, there are a few supplies you'll need to get before you can crack on with cleaning the patio.

What you'll need

Headshot of Jonathan Kirby
Dr. Jonathan Kirby

Dr. Jonathan Kirby is a developmental chemist at Roxil, Safeguard Europe. From pest control to masonry protection, he has dedicated himself to helping protect UK housing stock through the development of new and innovative materials. Jonathan is the go-to garden expert at Roxil for tips on how to protect garden patios, paving and outdoor wooden structures from the elements.


1. Get prepped for cleaning

Sand coloured concrete paving stones with plants and garden chairs

(Image credit: MKM)

The first step to learning how to remove black spots from patio is to grab your brush and sweep away any debris. Dirt, gravel, leaves, and anything else that likes to find a home on your patio needs to be removed before moving on to the next step. Make sure to clear the space of any plant pots or garden furniture too.

2. Choose your cleaner

Grey patio with square paving stones, black table and chairs

(Image credit: Topps Tiles)

Black spots show up on patio slabs when mould and algae have taken root in the pores of the flags, so while it is possible to remove them, you're going to need the help of one of the best patio cleaners

'I recommend using a specially-formulated black spot remover, such as Rob Parker's Best Patio Cleaner,' says Ivo Iv, Founder, Decor Home Ideas.  'This product can be used on all types of stone surfaces and will not only kill the black spot permanently but also bleach the blackness out of the visible black spot.'

There are plenty of mould-removing patio cleaners on the market, just double-check that they're safe to use on your patio's material. 'Watch out for acid or bleach-based cleaners as these can damage the patio surface, and instead opt for a soft, non-destructive patio cleaner,' Jonathan says. 

Wet & Forget Mould, Lichen & Algae Remover - 5 Litre, was £34.99 now £26.38 at Amazon

Wet & Forget Mould, Lichen & Algae Remover - 5 Litre, was £34.99 now £26.38 at Amazon

The Wet and Forget Mould, Lichen and Algae remover has a non-bleach formula that is ideal for cleaning any type of patio surface. Mix one part product to five parts litre for effective removal of black spots, and you'll be able to use it 30 times over if they come back.

3. Or make a natural cleaning solution

You can also try cleaning with vinegar or baking soda. These are powerful cleaning agents that help to decompose bacteria, and they work wonders for removing mould and mildew from outdoor cushions. Experts say they can do the trick for the patio as well. 

'You can remove black spots easily from patios in an eco-friendly, low-cost way, with white vinegar,' says Laura Harnett, Founder, Seep. 'It has antifungal and antibacterial properties and will also stop the mould or lichen growing back. Mix a paste in a bowl using one part baking soda, one part white vinegar and one part hot water.'

3. Apply your cleaner

Grey concrete slabs with stove burner

(Image credit: Topps Tiles)

Next, apply your chosen cleaning agent to your patio. Be generous; the more solution you apply, the more likely those black spots are to lift. Wait at least 15 minutes before moving on to the next step, to allow the solution to work its magic. Special patio cleaners may need longer to activate, with some products recommending waiting 24 hours before scrubbing, so check the manufacturer label after you apply.

'Wear gloves to protect the skin and then apply the cleaner with a spray or wire brush, either neat or diluted depending on the space / size of your patio,' says gardening expert Jonathan.

4. Scrub away

'Grab a stiff-bristled brush and scrub the black spots,' says Sarah Clemence, Cleaning Blogger, Busy Blooming Joy. 'Put some elbow grease into it; you'll see them start to disappear.'

How much scrubbing you need to do will depend on how many black spots are on your patio, and the type of cleaner you're using. White vinegar and baking soda solutions will need to be worked into the slabs in order to activate. Some patio cleaners will do most of the work for you, and you may find after leaving it to sit on your patio for 24 hours that most of the black spots have lifted. 

5. Rinse away

Grey concrete patio with planters and sliding french doors

(Image credit: Topps Tiles)

'Finally, rinse the area with water, either with a hose or a low-pressure setting on a one of the best pressure washers - high pressure might damage the pointing between slabs,' says Sarah.

As your cleaning solution washes away, the black spots on the patio should disappear with it. You may need to repeat the process for stubborn spots that have been settled on your patio for a while. 

And that's it! Five simple steps and you've successfully learnt how to remove black spots from patio.


What causes black spots on patio slabs?

'Due to moisture and shaded areas, black spots on patio slabs are often caused by mold, mildew, or lichen growth,' explains Amber Noyes, Horticulturist and Editor, Gardening Chores. 'It's essential to tackle this issue as soon as you notice it because these organisms can damage the patio over time.'

Though this is a common issue, it's important to learn how to remove black spots from patio as soon as you notice them. 'Black spots require moisture to grow and then take root in the pores of the patio flags,' explains Jonathan from Roxil. 'This is why it’s so important to waterproof the patio when laying it to prevent the black spots from arising in the first place.'

Not waterproofing the patio or installing adequate drainage is one of the most common patio mistakes, and will lead to black spots appearing on your slabs more frequently.

Can I use a pressure washer to remove black spots from patio?

While it is generally safe to use your pressure washer on your patio, this alone is not going to be enough to remove black spots completely, and if you go in with a high pressure, you risk damaging the pointing between the patio slabs. 

'While it's tempting to blast away to remove black spot lichen, pressure washing on a high setting can damage the patio, blow out pointing and disperse jointing sand,' Jonathan explains. 'Take extra care and keep the pressure low.'

'Pressure washing is another method that some people turn to, but it's not always effective, especially if the black spots have been around for a long time,' Ivo from Decor Home Ideas agrees. 'In such cases, you might want to consider high-temperature, low-pressure steam cleaning instead, like the Doff system.'

Does bleach remove black spots on patio?

Bleach can remove black spots from patio, but it's a harsh chemical that will potentially damage some paving materials. It's also not good for the environment, and something you should avoid using if you've got plants near your patio area.

'I prefer using a vinegar solution as it's more environmentally friendly and less harsh on your patio surface,' says Amber Noyes. 'If you decide to use bleach, dilute it with water (1 part bleach to 10 parts water) and wear protective gear, such as gloves and goggles.'

Katie Sims

Katie Sims has been writing for Ideal Homes since spring 2022. She qualified from her Master’s in Media and Journalism in 2021 and has been writing freelance since. She has worked on Ideal Home’s ecommerce team where she researched the best home products on the market, and on the news team, researching the latest trends for feature pieces.