The first warm Saturday of late May is when most British driveways get their annual seeing-to. Out comes the pressure washer from the back of the shed, the trigger gets pulled, and within twenty minutes half the kiln-dried sand is in the flowerbed and a pale, etched stripe of raw concrete is glaring back from the block paving. By July the weeds are through again, the blocks are wobbling under the bin wheels, and you are looking at a £350 quote to re-sand and re-seal the lot.
Why driveways look worse after a power-wash, not better
The damage almost always comes from two compounding mistakes. The first is a zero-degree pencil nozzle held too close. A 0° lance on a Karcher K5 puts roughly 145 bar into a coin-sized dot — that will shift moss, but it will also etch the concrete surface, scrub off the factory slurry layer, and blow every grain of kiln-dried sand into next door's lawn. The second is washing in straight back-and-forth passes with that pencil jet, leaving tiger-stripes that no sealer will ever hide.
The kit that actually does the job
You do not need a petrol monster. A mains domestic washer with a surface-cleaner attachment is the correct tool for a typical 40-60 m² drive:
- Karcher K4 Premium Full Control Home — around £230 at Wickes. 130 bar is perfectly adequate.
- Karcher K5 Premium Smart Control — around £330. Extra pressure helps with bad black spot.
- Karcher T-Racer T5 surface cleaner head — £75-£90 at B&Q or Screwfix, and the single most important purchase on the list. It encloses two rotating jets inside a brush skirt and keeps the spray pattern even.
- Kiln-dried jointing sand — about £6 a 25 kg bag at Travis Perkins. A 60 m² drive needs four bags.
- Block paving sealer (optional) — Smartseal Natural Look at £45 for 5 litres, or Resiblock Superior at £80 for 5 litres if you want the deepest "wet look". One 5-litre tin covers 20-25 m².
- A stiff yard brush, a soft pushbroom for sand, knee pad, ear defenders. The K5 is louder than people remember.
The order that stops you ripping the joints out
- Kill the weeds a week earlier. Spray visible weeds with Roundup Optima+ or pet-safe Weedol Pathclear at least seven days before. Power-washing live weeds out of a joint blows the roots deeper.
- Sweep before you spray. A proper sweep removes the loose grit that, driven sideways by 130 bar, chips block edges.
- Pre-treat heavy black spot. Those black freckles are artillery fungus. Pour Wet & Forget patio cleaner (£15 a litre at Toolstation) neat onto the worst patches, leave twenty minutes, then wash.
- Fit the T-Racer. On a K5, set the variable trigger to middle, not flat-out. The rotating jets inside the surface cleaner are already doing the agitation.
- Wash in overlapping straight lines, half-block overlap. Move at the pace of a slow walk. Don't dwell. Don't lift the skirt off the surface.
- Let it dry for at least four hours on a 20°C day. Kiln-dried sand only flows into the joint when both joint and sand are bone dry.
- Brush new sand in dry. Tip a bag out in a heap, sweep diagonally across, then sweep the other diagonal. Joints should fill to about 2 mm below the chamfer.
- Seal only when everything is dry. Dry blocks, dry joints, dry forecast for 24 hours. A roller is faster than a sprayer for the panels.
The bits the YouTube videos skip
Two things genuinely catch people out. First: do not seal new block paving in its first six months. The blocks need to off-gas residual moisture from the factory pallet, and sealing it in produces a milky bloom that nothing short of an acid wash will lift. Second: the surface cleaner will not reach the 30 mm strip along the kerb edge, the garage door, or around drain gullies. You have to do those by hand with a 25° fan nozzle, low pressure, held 30 cm back.
One more thing the trade always mentions and homeowners always forget: cover drain gullies and air bricks with an offcut of plywood before you start. Kiln-dried sand washing into a soakaway is what turns a clean driveway into a £180 drain rod callout three weeks later.
What it costs vs the contractor
A landscaper round my way quotes £8-£12 per square metre to clean, re-sand and seal a domestic drive — so £400-£700 for a typical two-car layout. Doing it yourself with a K5 and a T-Racer you already own costs about £30 in sand and £45 in sealer for a 60 m² drive. Buying the kit from scratch is still under £400, and you have the washer for the car, fence and patio furniture for the next ten summers.
The damage on this job happens fast — too close, too narrow a jet, too much trigger — and almost never from being too gentle. If you finish your drive and it looks slightly less clean than the neighbour's professional one but the joints are still full of sand and the blocks aren't fuzzy at the edges, you have done it better than the contractor and saved yourself £500.