Patio cleaning: the 2-product trick with soda crystals and washing-up liquid

Rather than relying on a noisy machine, however, a simple combination of two everyday products is enough.

As soon as the weather turns warmer, every mark becomes visible: green growth, 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 instead relies on a surprisingly straightforward, inexpensive and gentler method, using just two household products and no pressure washer at all.

Why the patio looks so bad after winter

For months, rain, frost and shade take their toll on paving slabs, block paving and concrete. Moisture lingers in the joints, leaves rot, and sand and dust build up. These are ideal conditions for algae, moss and lichen. The result is a streaky green film that can make the entire outdoor space appear neglected.

There are also several typical trouble spots:

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

Many attempt to tackle this as aggressively as possible: a pressure washer at full power, strong bathroom cleaner, chlorine bleach or highly concentrated vinegar. The immediate effect can often look impressive. Over time, though, it damages the surface, the joints and, in some cases, the garden too.

Why vinegar and similar cleaners need care

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

The garden can suffer as well. If the acidic solution runs into flower beds or onto the lawn, it changes the soil’s pH level. Sensitive plants may respond with yellow leaves or poor growth, particularly in small gardens where everything is close together.

Pressure washers present a different issue. Their forceful water jet can dislodge jointing material, wash away sand and roughen the stone surface. As a result, fresh dirt can settle more quickly afterwards. On older patio slabs, the jet may even break small fragments from the stone.

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

The surprisingly simple 2-product trick

The British DIY enthusiast “Fix it with Fowlers” uses a blend of soda crystals and washing-up liquid. Both are available from supermarkets or household retailers, often for just a few pounds.

What soda crystals actually do

Soda crystals, also called washing soda, are a long-standing laundry staple. This strongly alkaline substance breaks down grease, dirt and much of the organic build-up. On patio slabs, it helps tackle:

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

Importantly, soda crystals are not the same as caustic soda or drain cleaner containing sodium hydroxide. The latter are considerably harsher and unsuitable for outdoor stone slabs.

Why washing-up liquid completes the mixture

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

• barbecue grease and food residue
• oil marks from bicycles, pushchairs or cars
• a fine film of dirt from exhaust fumes

An ordinary colourless washing-up liquid is perfectly adequate. Anyone seeking an especially environmentally considerate option can choose an ecologically certified product.

Cleaning a patio with soda crystals and washing-up liquid

This method does not depend on high-tech equipment, but on preparation and allowing enough time for it to work. The basic routine can be used on virtually any patio, whether it has concrete slabs, concrete block paving or hard-wearing natural stone.

• Clear the joints: First, remove weeds with a patio weeding tool or narrow trowel. This allows the cleaning solution to reach every corner later on.
• Sweep thoroughly: Use a stiff broom to clear away sand, leaves and coarse 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 covering across the whole area is sufficient. Avoid forming thick piles.
• Apply the washing-up liquid: Drizzle a few lines of washing-up liquid over the surface; do not overdo it, or it will foam excessively.
• Scrub it in: Scrub in circular motions with a stiff deck brush until a light film forms over the slabs.
• Leave it to work: Keep the mixture 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.

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

Safety and common patio-cleaning mistakes

Although soda crystals are considerably gentler than many specialist cleaners, a few precautions are still necessary:

• Avoid contact: It is best to wear gloves when mixing and scattering them. The alkaline solution can further irritate dry skin.
• Keep children and animals away: Pets and children playing should stay off the area while the surface is wet.
• Test sensitive stone: For pale sandstone or highly polished slabs, first clean an inconspicuous corner 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 a gentle clean, or using 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 cleaner for longer

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

• sweep briefly every fortnight, especially after storms and heavy pollen
• move plant pots from time to time so that permanently damp patches do not form underneath
• 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. This means the patio enters winter much cleaner, less algae can establish itself, and the work is more manageable in spring.

What algae, moss and lichen really are

Many people mistake green patio growth for “mould”. In reality, it is usually algae and moss, which thrive in damp, shaded corners. Lichen - the white or pale grey, crust-like patches - 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 exactly why a gentle cleaning approach that does not further roughen the stones 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 entirely. It can be useful for thick layers of mud after building work or hardened clumps of soil. In that case, you should:

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

For older patios, loose joints and sensitive natural stone, however, the gentle 2-product mix offers considerably more. It cleans deeply enough to create a well-kept appearance without “blasting away” parts of the patio year after year.

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