How to Clean a Patio Before Winter: Methods by Surface

A patio that's green, slippery and stained in October will be worse by March. Autumn is the moment to clean it, because you remove the algae, moss and leaf stains before months of rain and frost settle into the joints. The good news is that you don't always need a pressure washer. Below I've set out the methods by surface, the order to work in, and the mistakes that damage slabs and pointing.

Quick answer: which method suits your patio?

Patio surface	Best cleaning method	Watch out for
Concrete slabs	Stiff brush and patio cleaner, or a pressure washer on a wide fan nozzle	Etching the surface with a narrow jet held too close
Indian sandstone	Soft brush and a stone-safe cleaner, or a low-pressure rinse	Acid or bleach cleaners, which can stain and fade the stone
Porcelain tiles	Warm soapy water and a soft brush; a pressure washer is usually fine	Sealant residue and grout damage from a strong jet
Block paving	Pressure washer with a rotary surface cleaner, then re-sand the joints	Blasting out the jointing sand and loosening blocks
Natural slate or limestone	Gentle, pH-neutral cleaner and a soft brush	Anything acidic, including vinegar
Composite or timber decking	Deck cleaner and a stiff brush along the grain	Raising the grain or splintering timber with high pressure

If you're not sure what your patio is made of, test any cleaner on a small, hidden corner first and wait a day before you do the rest.

What you'll need

• A stiff outdoor brush and a smaller hand brush for corners
• A patio cleaner suited to your surface (check the label for stone types)
• A garden hose or a pressure washer, if your surface can take it
• A weeding knife or old kitchen knife for the joints
• Kiln-dried sand or jointing compound for block paving
• Gloves, eye protection and old shoes with a good grip
• A bucket of warm water with a squeeze of washing-up liquid for light jobs

How to clean a patio step by step

1. Clear everything off. Move furniture, pots and the barbecue so you can reach every slab.
2. Sweep thoroughly. Get leaves, soil and loose moss off first, otherwise you're just pushing mud around.
3. Weed the joints. Run a weeding knife along the gaps to lift weeds and moss before you wet anything.
4. Wet the surface with plain water. A damp patio absorbs less cleaner, so it stays on the surface where it's needed.
5. Apply your cleaner. Follow the dilution on the bottle and work in sections of a few square metres.
6. Scrub. A stiff brush lifts most green algae; go along the joints as well as across the slabs.
7. Rinse or pressure wash. Work from the house outwards so dirty water runs away from your walls and doors.
8. Let it dry, then check. Some stains only show once the surface is dry, so look again the next day.
9. Re-sand or re-point where needed. Brush kiln-dried sand into block paving joints, and repair any crumbling mortar on slab patios.

Pressure washer or brush?

A pressure washer is quick and satisfying, and on concrete or block paving it saves hours. But it's easy to overdo it. A narrow jet can etch concrete, strip the surface from sandstone and blast mortar out of joints, which lets weeds back in faster. If you use one, start on the lowest setting, use a wide fan nozzle or a rotary patio attachment, keep the lance moving and hold it at an angle rather than straight down.

A brush and the right cleaner is slower but kinder to natural stone and older patios. Many people find a mix works best: scrub with a cleaner, then give a gentle rinse. If your patio is mainly concrete or you also have a driveway to tackle, my guide to pressure washing a driveway covers attachments, technique and how to avoid streaks.

How to get rid of green algae and black spots

Green algae is the most common problem and usually comes off with a scrub and a patio cleaner. Black spots on sandstone are usually lichen, which grips harder and needs a dedicated lichen or black spot remover and some patience. Apply it, leave it for the time stated on the label, and expect to repeat the treatment. Don't try to blast lichen off with a narrow jet, as you'll damage the stone before the spots move.

Moss in the joints responds best to being scraped out and then kept dry. If the same corner turns green every year, look at why it stays damp: overhanging shrubs, a blocked drain or a gutter dripping onto the paving are the usual culprits.

Natural cleaners: what works and what to avoid

• Warm water and washing-up liquid is fine for light dirt on porcelain and concrete.
• Oxygen-based cleaners are gentler on plants and pets than bleach, and they work well on algae.
• Bicarbonate of soda paste can help with small grease marks from a barbecue.
• Vinegar is popular online, but it's acidic and can damage limestone, marble and some sandstone, so keep it off natural stone.
• Bleach can discolour stone and harm nearby plants and lawns, so most people are better off with a product made for patios.

When to clean your patio

Early to mid autumn is ideal. Temperatures are usually still above freezing, which matters because water left in joints and cracks can freeze, expand and lift slabs or crack mortar. Pick a dry spell with a couple of days without heavy rain so cleaners can work and the surface can dry. A lighter clean in spring then keeps it looking good through summer.

Protecting your patio through winter

• Clear fallen leaves every week or two, because wet leaves stain slabs and feed algae.
• Keep drains, gullies and the edges of the patio clear so water runs away.
• Lift plant pots onto pot feet so water doesn't sit underneath them and leave rings.
• Cover or store garden furniture so it doesn't rust or mark the slabs.
• Consider a sealer for porous stone once it's clean and fully dry, following the product instructions.
• Use a de-icing product that's safe for your surface rather than rock salt on natural stone.

A clean patio is one job on a longer autumn list. If you're working through the whole house and garden, my autumn home winter-proofing checklist covers gutters, pipes, boilers and draughts in one place.

Common mistakes to avoid

• Holding a pressure washer nozzle too close, which leaves stripes and pitted patches.
• Using acidic cleaners on natural stone.
• Forgetting to re-sand block paving joints after washing.
• Cleaning just before a hard frost, so water freezes in the joints.
• Letting dirty water run against the house or into an airbrick.
• Skipping eye protection when you're working with a pressure washer or strong cleaner.

Is it worth paying someone to do it?

If your patio is large, made of delicate natural stone or badly stained, a specialist cleaning company can be worth it. They'll usually have rotary cleaners and the right products, and they can reseal the surface afterwards. Ask whether they'll re-sand or re-point joints, what cleaner they use on your stone type, and whether they carry insurance. A clean, tidy patio also helps if you're thinking about selling, and my guide to home improvements that add value explains which outdoor jobs buyers notice.

A simple routine that keeps it clean

The easiest patio to clean is one that never gets too bad. Sweep it every week or two, deal with leaves and spills quickly, pull weeds while they're small, and give it a full clean once or twice a year. Little and often beats a weekend of hard scrubbing every spring.

Do you know a clever trick for outdoor cleaning or garden upkeep that other homeowners should hear about? I'm always happy to hear from people who write about home improvement and want to share practical know-how.

Frequently asked questions

What is the best way to clean a patio without a pressure washer?

Sweep and weed the joints, wet the surface, apply a patio cleaner suited to your stone, scrub with a stiff brush and rinse with a hose. Repeat on stubborn areas.

Can you pressure wash Indian sandstone?

You can, but carefully. Use a low setting and a wide fan or rotary attachment, keep the nozzle moving and never use a narrow jet close to the stone.

Does vinegar clean a patio?

It can lift light dirt from concrete, but it's acidic and can damage limestone, marble and some sandstone. A cleaner made for your surface is safer.

How do you stop a patio going green?

Keep it swept and dry, clear leaves, cut back overhanging plants, fix dripping gutters and clean it once or twice a year.

When is the best time to clean a patio?

Early to mid autumn, before frosts, and again in spring. Choose a dry spell so the surface and joints can dry out.