Patio Cleaning: The 2-Product Trick with Soda Crystals and Washing-Up Liquid

Rather than relying on a noisy machine, a straightforward blend of two everyday products can do the job.

As soon as the weather turns warmer, every mark outside becomes obvious: green deposits, black streaks and rusty rings beneath chair and table legs. Many people instinctively reach for a pressure washer, chlorine cleaner or concentrated vinegar. One British DIY enthusiast, however, relies on a surprisingly simple, inexpensive and gentle method using just two household products – with no pressure washer required.

Why patios look so bad after winter

Months of rain, frost and shade take their toll on stone slabs, paving and concrete. Moisture sits in the joints, leaves decay, and sand and dust become embedded. These are ideal conditions for algae, moss and lichen. The result is a streaky green film that makes the entire outdoor area look neglected.

There are also several familiar trouble spots:

• Rust stains caused by the metal feet of chairs, tables or parasol bases
• Brown marks left by plant pots and water run-off
• Grease and barbecue residue around the barbecue
• Black scuffs from rubber feet or shoe soles

Many people try to tackle this with maximum force: a pressure washer on full power, harsh bathroom cleaner, chlorine bleach or highly concentrated vinegar. It can look impressive in the short term, but over time it can damage the surface, the joints and, in some cases, the garden as well.

Why vinegar and similar cleaners need careful use

Vinegar is often viewed as a “natural” and therefore harmless option. It is still an acid, however. On certain natural stones, it may leave fine scratches and dull patches. Repeated treatment can gradually make the surface look increasingly matt and blotchy.

The garden may suffer too. If the acidic solution drains into flowerbeds or lawns, it changes the soil’s pH level. Sensitive plants can respond with yellow leaves or poor growth, especially in small gardens where everything is close together.

Pressure washers create a different issue. Their powerful jet can dislodge jointing material, wash away sand and roughen the stone’s surface. New dirt then sticks more readily later on. On older patio slabs, the force can even break small fragments away from the stone.

“The mix of two simple household remedies cleans thoroughly without eating away at stone and joints – while also staying far quieter than a pressure washer.”

The surprisingly easy 2-product trick

British DIY enthusiast “Fix it with Fowlers” uses a combination of soda crystals and washing-up liquid. Both are available from supermarkets and household shops, often for only a few pounds.

What soda crystals actually do

Soda crystals, also known as washing soda, are a traditional laundry product. This strongly alkaline substance breaks down grease, dirt and much of the organic build-up. On patio slabs, it can help remove:

• baked-on road grime
• grey, weathered deposits
• green algae growth

Importantly, soda crystals are not the same as caustic soda or drain cleaner containing sodium hydroxide. Those products are far more aggressive and unsuitable for outdoor stone paving.

Why washing-up liquid completes the mixture

Washing-up liquid is familiar from the kitchen: it cuts through grease, breaks up oily films and helps water penetrate dirt more effectively. On a patio, it is particularly useful for:

• barbecue grease and food residue
• oil traces from bikes, pushchairs or cars
• a fine layer of grime from exhaust fumes

An ordinary clear washing-up liquid is entirely sufficient. Anyone looking for an especially environmentally considerate approach can choose an ecologically certified product.

How to clean a patio step by step

This method depends not on high-tech equipment, but on preparation and contact time. The basic process can be used on almost any patio, including concrete slabs, concrete block paving and durable natural stone.

• Clear the joints: First remove weeds using a patio-joint scraper or narrow trowel. This allows the cleaning solution to reach every corner afterwards.
• Sweep thoroughly: Use a stiff broom to clear away sand, leaves and loose debris. The cleaner the starting surface, the better the result.
• Wet the area: Evenly soak the slabs with a garden hose or watering can. This helps the soda crystals dissolve more effectively.
• Scatter the soda crystals: A light coating across the whole area is enough. Avoid creating thick piles.
• Apply the washing-up liquid: Drizzle a few lines of washing-up liquid over the surface. Do not use too much, or it will foam excessively.
• Scrub it in: Work in circular motions with a stiff scrubbing brush until a light film forms over the slabs.
• Leave it to work: Let the mixture remain on the surface for up to 48 hours. Ideally, there should not be heavy rain during this period.
• Rinse afterwards: Finally, rinse the patio thoroughly with the hose until no foam or residue remains visible.

“Patience replaces the pressure washer: the mixture of soda crystals and washing-up liquid needs time, but it works gently and quietly.”

Safety and common patio-cleaning mistakes

Although soda crystals are considerably gentler than many specialist cleaners, several precautions still matter:

• Avoid contact: It is best to wear gloves when mixing and scattering the product. The alkaline solution can further irritate dry skin.
• Keep children and animals away: Pets and playing children should stay off the area while it is wet.
• Test sensitive stone: On pale sandstone or highly polished slabs, clean a hidden corner first and check whether the colour or surface changes.
• Do not mix with other chemicals: Do not add bleach, drain cleaner or aggressive bathroom cleaners. Combining them can cause unpredictable reactions.

A major mistake made by many homeowners is returning to the pressure washer after using a gentler treatment, or applying aggressive mould remover in between. Each time, the patio loses a little more material, joints begin to crumble and nearby plants suffer.

How to keep the patio clean for longer

Following a thorough deep clean, the work required for the rest of the season can be reduced significantly. A few simple habits will help the surface stay tidy for longer:

• give it a quick sweep every two weeks, particularly after storms and heavy pollen fall
• move plant pots from time to time so that permanently damp patches do not form beneath them
• place the barbecue and fire pit on a fireproof base
• treat heavy stains, such as red wine, oil and bird droppings, as quickly as possible with water and a little washing-up liquid

In late autumn, it is worth repeating the 2-product trick more lightly. The patio will then enter winter much cleaner, fewer algae will settle, and the spring clean will be more manageable.

What algae, moss and lichen really are

Many people mistake green patio deposits for “mould”. In reality, they are usually algae and mosses, which thrive in damp, shaded corners. Lichen – the white or pale grey crust-like marks – consists of fungi and algae living together, and grows extremely slowly.

None of the three has any regard for attractive garden furniture. The rougher and dirtier the surface, the more easily they take hold. That is precisely why a gentle cleaning method that does not make the stones even rougher delivers better long-term results than any drastic treatment involving acid or high pressure.

When a pressure washer is worthwhile – and when it is not

A pressure washer should not be dismissed completely. It can be useful for thick layers of mud after building work or heavily caked-on clumps of soil. In that case, you should:

• set the pressure as low as possible
• work at a sufficient distance from the surface
• avoid sensitive joints or cover them up

For older patios, loose joints and delicate natural stone, the gentler 2-product mix is a much better choice. It cleans deeply enough for a well-kept appearance without “blasting away” parts of the patio every year.

Ultimately, the method shows that there is no need to buy half the DIY shop to keep an outdoor area in good condition. A pack of soda crystals, a bottle of washing-up liquid and a sturdy scrubbing brush are usually all that is needed to make slabs and paving look as though they have only just been laid.