Block paving driveways look brilliant when they're clean. The problem is that most advice for keeping them that way starts and ends with "hire a jet wash." And while a pressure washer can shift surface grime quickly, it's also one of the most effective ways to undermine the very thing that makes block paving look good; the jointing sand that locks the blocks together and keeps the surface stable.

The good news is that a pressure washer isn't actually necessary. With the right chemical cleaner and a methodical approach, you can get a block paving driveway cleaner than a jet wash produces, with results that last longer, and without disturbing a single grain of jointing sand.

Here's exactly how to do it.

Why Pressure Washing Block Paving Causes Problems

Before getting into the method, it's worth understanding what a pressure washer actually does to block paving because the problems aren't always immediately obvious.

It blasts out jointing sand: The sand packed into the joints between blocks is what keeps the surface stable, prevents individual blocks from shifting or rocking, and stops weeds from taking root. High-pressure water directed into the joints removes this sand, sometimes significantly. Over successive pressure washes, joints become loose, blocks begin to move, and the surface can become uneven. Reinstating jointing sand is a fiddly, time-consuming job.

It opens up the surface: Block paving, particularly concrete block paving, has a relatively porous surface structure. The mechanical action of high-pressure water erodes the surface of individual blocks, increasing porosity and making them more susceptible to staining, biological growth, and moisture penetration in subsequent months. You clean aggressively, the surface becomes more vulnerable, growth returns faster and the cycle repeats.

It spreads biological growth: The high-velocity spray from a jet wash physically dislodges algae, mould, and lichen from the surface, but doesn't kill the spores. Those spores get distributed across the surrounding area, often onto lawns, flower beds, adjacent paving, and into the joints between blocks. Growth re-establishes, often across a wider area than before.

It doesn't address the cause: Green algae, black spots, and mould don't just sit on top of block paving, they embed their root structures into the porous surface. A pressure washer removes what's visible above the surface. The roots embedded beneath remain, and drive regrowth from exactly the same spots.

What You'll Need

To clean a block paving driveway without a pressure washer, you need:

• GK Driveway Cleaner 5Ltr - for general algae, mould, and biological staining
• GK Black Spot Remover 5Ltr - if black lichen spots are present (common on block paving)
• GK Oil Out 5Ltr - if there's oil or fuel staining from vehicles
• A garden pump sprayer (standard 5-litre garden sprayer works well)
• A stiff-bristled brush (for spot areas or heavy soiling)
• A bucket and measuring jug for dilution
• Protective gloves and eye protection

For most driveways, GK Driveway Cleaner alone handles the cleaning. Black Spot Remover is an additional treatment for the persistent dark lichen spots that biocide cleaners alone often can't fully shift. Oil Out is only needed if there's oil staining - it's not a substitute for the biological cleaner.

Step-by-Step: Cleaning Block Paving Without a Pressure Washer

Step 1: Clear and Sweep the Surface

Remove everything from the driveway including vehicles, plant pots, bins, or anything sitting on the surface. Then sweep thoroughly to clear loose debris, leaves, and any loose surface dirt. Pay particular attention to the joints between blocks, where leaf debris and organic material tend to accumulate and retain moisture.

If there's any significant moss growth sitting loose on the surface, a stiff brush over the whole area before treatment will help, but don't scrub hard as you want to remove what's loose, not disturb jointing sand or abrade the blocks.

Step 2: Identify What You're Dealing With

Before mixing and applying, take a few minutes to note what kind of contamination is present:

• Green or grey-green film across the surface - general algae and mould. Treat with GK Driveway Cleaner.
• Black or dark brown spots - black lichen (black spot). These require separate treatment with GK Black Spot Remover, as standard biological cleaners often can't penetrate the hard, protective outer crust of lichen. Treat these after the initial Driveway Cleaner application.
• Orange or reddish-brown marks - rust staining, likely from metal gate hinges, fence posts, or vehicles. This requires GK Stinky Pinky Rust Remover, not a biological cleaner.
• Dark staining in a concentrated area near the road edge or parking spot - likely vehicle oil or fuel. Treat with GK Oil Out before or after the biological cleaner.
• White or chalky deposits on block surfaces or rising from joints - efflorescence (salt deposits). These require GK EFF OFF Efflorescence Remover, not a biological cleaner.

Getting the right product onto the right problem saves a lot of repeated effort.

Step 3: Mix and Apply GK Driveway Cleaner

GK Driveway Cleaner is a concentrated formula - never apply neat. Mix in a clean bucket or directly in your garden sprayer:

Heavy soiling (dense green growth, heavily contaminated surface, not cleaned in over a year): dilute 2:1 - 2 parts water to 1 part product.

Light to medium soiling (annual maintenance, moderate growth): dilute 4:1 - 4 parts water to 1 part product.

A 5-litre bottle of concentrate diluted to 4:1 gives you 25 litres of working solution, covering approximately 100m², which is enough for a standard driveway in a single treatment.

Apply the working solution to the dry block paving surface using your garden sprayer. Work systematically, section by section, overlapping slightly to ensure even coverage. GK Driveway Cleaner is a natural surfactant, so it will foam on contact with the surface. This foam is a useful coverage indicator: if an area isn't foaming, it hasn't been adequately treated.

The formula is free from bleach, solvents, and acids, so there's no risk of discolouration or surface damage from overspray onto adjacent materials. If you accidentally overspray onto adjacent plant life, rinse with clean water as the formula may cause minor foliage scorch but won't kill established plants, and grass recovers quickly.

Step 4: Allow Dwell Time - Don't Rush This

This is the step that most people skip or cut short, and it's also the most important.

GK Driveway Cleaner works by penetrating the porous block surface and killing biological growth at root level, the algae spores and mould mycelium embedded into the material, not just the visible surface growth. This biological kill requires contact time.

Leave the product on the surface and allow it to work. For best results, apply on a dry day when no rain is forecast for at least 24 hours. A slightly cool, overcast day with no wind is ideal as warmer, windier conditions cause the working solution to evaporate faster, reducing contact time.

There's no need to rinse at this stage. GK Driveway Cleaner is designed to work with natural weather cycles. Once applied, rain and UV over the following days and weeks continue breaking down the dead biological material and washing it from the surface naturally.

Results timeline:

Mild staining: visible improvement within a few days

Moderate contamination: 2-3 months for full results

Severe or long-established growth: up to 6-12 months for complete clearance

This longer timeline isn't a product limitation, it's how biological cleaning works. The difference is that the results, when they come, are far more complete and last significantly longer than a pressure wash, because the growth has been killed rather than physically removed.

Step 5: Treat Black Spots Separately (If Present)

If your driveway has dark black or brown spots, distinct from the general green film, these are black lichen and they need separate treatment.

Black lichen forms a hard, protective outer crust that standard biological cleaners can't penetrate reliably. The fungal component buries root structures (called hyphae) deep into the pores of the block surface. You need a product specifically formulated to dissolve that bond.

GK Black Spot Remover uses a semi-gel, thixotropic formula that is slightly viscous, so it clings to the block surface rather than running off into the joints, with a unique alkali formula enriched with wetting agents. Unlike thin liquid cleaners, it's designed for extended dwell times of up to 24 hours, which is what's needed to fully penetrate and dissolve the lichen.

Apply directly to the affected areas with a brush or sprayer. Allow to dwell for as long as possible - several hours minimum, overnight for well-established spots. Don't rinse immediately; let the formula do its work. One 5-litre bottle treats up to 40m² of affected surface.

Step 6: Treat Oil Staining (If Present)

Vehicle oil and fuel staining on block paving requires a different type of product as a biological cleaner won't lift petroleum-based staining.

GK Oil Out is applied ready-to-use (no dilution) directly onto the stained area. Leave it to work for up to an hour, then rinse with hot water. For deep-set or long-established staining, repeat the application. Coverage is around 4-6m² per litre depending on surface porosity.

Oil Out can be applied before or after the biological cleaner. If the driveway has both oil staining and algae, it's usually easiest to treat oil spots first, allow them to clear, then apply Driveway Cleaner across the whole surface.

Step 7: The Light Rinse (Optional)

Once you've applied all necessary treatments and allowed adequate dwell time, a light rinse with a garden hose on a gentle setting can help remove surface residue and speed up the visible clearance of dead biological material.

This is optional as the natural weather cycle will do this work for you over the following weeks, but if you want to see faster visible results, a gentle hose-down (not a pressure washer) after at least 24 hours of dwell time will help.

The key word is gentle. You're rinsing, not blasting. Keep the hose on a low, flat flow rather than a jet setting, and work in the direction of natural drainage to avoid pushing water into areas you've already treated.

How to Keep Block Paving Clean for Longer

The single most effective thing you can do after cleaning is to apply a block paving or invisible stone sealer. A penetrating sealer soaks into the surface of the blocks and creates a moisture-repelling barrier from within, dramatically reducing the rate at which biological growth can re-establish and making any future cleaning significantly easier.

For a no-sheen, natural finish that doesn't alter the appearance of the blocks, GK Invisible Stone Sealer is the right product. Apply to a clean, fully dry surface (allow at least 48 hours after cleaning and rinsing) and the sealer will significantly extend the time between required treatments.

Beyond sealing, an annual maintenance application of GK Driveway Cleaner, even when the driveway looks relatively clean, takes far less product and time than a full remedial clean, because you're treating light biological loading before it builds to a heavy contamination. Once you've done the initial deep clean, keeping it clean becomes much easier.

Products Used in This Guide

Available from GK Products UK with free delivery on orders over £60:

Not sure which product is right for your driveway? Send a photo to the GK team at sales@gkproductsuk.com or call 07557 111 297 - we're happy to advise on the right treatment for your specific staining.