How to Clean Patio Slabs: The Complete UK Guide

Oct 06, 2025

A clean patio not only looks better, but it’s safer to walk on and looking after your slabs means they’ll last longer too. Knowing how to clean patio slabs is vital for looks and longevity.

Whether you’re dealing with slippery algae, stubborn black spot, or everyday grime, the right method can make a big difference.

Here we share our tips and tricks for manual scrubbing, stone-safe chemicals, eco-friendly options, and careful pressure washing, then guide you on how to use each of them.

Follow our guidance and simple maintenance plan to keep your slabs looking their best all year round.

Common patio slab problems you’re likely dealing with

Algae, moss and lichen: Green or dark films that make your patio slick, this stuff thrives in damp and shaded areas.
Black spot: These tiny, tar-like dots are lichen. They especially occur on sandstone and sometimes porcelain, and often resist basic cleaning.
General grime: Dust, soil, and air pollution will all dull the surface of your patio over time.
Rust marks: Orange-brown stains from metal feet of furniture, BBQs or fertiliser spillages are annoying, but thankfully can be removed.
Oil or grease: Splashes from booking or vehicles that will soak into porous stone.
Efflorescence: Powdery white salt deposits, which are caused by moisture drawing them to the surface of your patio.
Weeds in joints: Growth through or between pointing where sand or mortar has thinned or cracked.

Protecting your patio

Not only do you need to protect yourself whilst you’re cleaning, but there are also some key points we’d like to make before you begin:

Always carry out a small test patch in a discreet corner to check how your stone reacts, especially if you’re using chemicals.
Shield your plants and lawns to prevent damage.
Always follow the manufacturer’s advice.

Tools and materials checklist

Having the right kit to hand makes the job safer and easier to do. Here are some things you’ll need:

A stiff outdoor brush, bucket, spray bottle or watering can
A scraper or wire brush for stubborn areas
Mild detergent, white vinegar, or bicarbonate of soda
Oxygen bleach for stone-safe deep cleaning, avoid chlorine bleach
Specialist patio clear or black spot remover (Always check pH and stone compatability)
A pressure washer with adjustable lance and fan nozzle, plus a hose
Jointing sand

Monthly upkeep clean

A monthly wash might seem a little taxing, but it’ll help to keep your patio slabs looking fresh and help stop dirt from building up.

Start by sweeping away loose leaves, soil and debris.
Pre-wet the slabs with clean water to reduce the chance of stains.
Mix a mild detergent solution and apply it across the surface.
Using a stiff outdoor brush, scrub the area to lift dirt and grime.
Rinse thoroughly with clean water and remove all residue.
Once the slabs are dry, check the joints and see if any jointing sand is needed for a top-up.

How to clean patio slabs: Deep clean methods

An eco-friendly clean

For light algae or general dirt, it’s worth starting with an eco-friendly solution. If any staining remains after this clean, you’ll probably want to step up to a specialist patio cleaner afterwards.

Mix one part white vinegar with one part water in a watering can or spray bottle.
Or dissolve oxygen bleach, following the manufacturer's instructions.
Apply generously and allow it to sit for 15-30 minutes.
Give it a little scrub with a stiff brush and rinse well with clean water.

Tackling black spots

Lichen, black spots that look like tiny, tar-like dots won’t shift with standard scrubbing. For this, you’ll want a specialist black spot remover that’s designed for patios and natural stone. You may need to repeat the process a couple of times to make a difference.

Apply the product evenly, following the instructions.
Leave to sit, sometimes it can be for hours.
Scrub with a stiff brush.
Rinse thoroughly.

Oil and grease stains

If oil is spilt, blot the area immediately with a kitchen roll; don’t wipe, or you’ll spread the stain.

For set-in marks, use a mix of bicarbonate of soda, cat litter, or diatomaceous earth mixed with a little detergent or water.
Apply the stain over the area, cover it with cling film or a tray, and leave it for a few hours before brushing away.
Repeat if needed.
For stubborn stains on porcelain, a solvent-based degreaser may be needed. Avoid using them on porous surfaces.

Rust stains

To treat rust stains, you’ll need a stone-safe remover that contains phosphoric or oxalic acid. Once you’ve treated the stains, rinse and neutralise with plenty of clean water.

Acid cleaners on limestone or other calcerous stones can result in permanent etches on the surfaces, so always double-check that products are safe for your surfaces.

White salts

Efflorescence is usually temporary and will go away over time, but if you want to remove it yourself:

Dry-brush the area regularly.
A light wash with clean water will help reduce its look.

Avoid using harsh acid-based cleaners, especially on sensitive surfaces. Patience is often the best treatment, as once the salts have stopped leaching out, the problem resolves itself naturally.

Using a pressure washer (without damaging your slabs)

A pressure washer is great for blasting away dirt, but if you don’t use it correctly, it can do more harm than good.

Always begin with a fan nozzle, rather than a pinpoint jet.
Keep the pressure on the lower side, around 1200-1600 PSI is usually enough.
Hold the lance at a shallow angle, keep it moving, and work in steady passes to avoid striping.
Never blast directly into joints or the edges of softer stones like limestone.
Once the patio is dry, re-sand the joints with kiln-dried sand or a suitable compound.
If slabs are loose or the pointing is fragile, you’re always best calling in the professionals to get it looked at.

Weed, moss and algae prevention

Like with most things, prevention is better than a cure. There are small things that you can do to stop weeds, moss and algae from building on your patio.

Improve drainage and allow more sunlight on your patio
Apply a stone-safe biocidal wash every few months
Re-joint with quality sand or compound
Block gaps where seeds may take root
Make a plan for seasonal sweeping in spring and autumn

Sealing your patio slabs

Sealing your patio slabs after you’ve cleaned them thoroughly can help to protect against stains, weathering and regrowth.

Sealers are designed to make the surface less porous, which means the dirt and algae take longer to return. Great if you want to reduce how much you actually have to spend cleaning them.

There are typically two types of sealers:

Breathable sealers: Allow moisture to escape
Film-forming sealers: Add a glossy or satin finish

The best sealer comes down to the stone you have, so double-check that it’s compatible with your own garden. And while it will need reapplying every few years, you can glory in the fact that it’ll help extend the life of your patio, as well as help it look its best over time.

How to clean patio slabs: A roundup

Cleaning your patio is worth the time and effort. Small regular cleans are best, and sealing it could be the way to go to help reduce your cleaning efforts over time.

The right method is all down to personal choice and what’s needed for your patio.

If you can’t seem to revive your current patio, we’ve got some beautiful patio options here at Ovation Landscaping. With a wide range of different stone types available, we’ve got your patios and driveways covered with our quality ranges.