Using a Karcher (Pressure Washer) on a Driveway or Patio

A domestic pressure washer — Karcher, Nilfisk, Bosch — will transform a tired driveway or patio in an afternoon, or ruin it in ten minutes. The difference is almost entirely technique.

The right pressure

Most domestic machines run 100–150 bar. That's plenty. What matters more is the nozzle and the distance:

• Fan / 25° nozzle: the default for driveways and patios.
• Rotary / turbo nozzle: fastest on concrete and block paving, but leaves striping if you're careless.
• Surface cleaner attachment (the round disc with two spinning jets underneath): the professional's choice. Even results, no striping, ~£40–£80 to buy.
• Pencil / 0° jet: never use on any driveway. It cuts holes.

Distance and angle

Keep the tip 25–40 cm from the surface at a shallow angle (30–45°). Move continuously — never linger. On resin and tarmac, keep to at least 40 cm.

Step-by-step

1. Sweep the area dry.
2. Pre-treat weeds and algae with a chemical killer 24 hours ahead.
3. Apply patio/driveway cleaner and let it dwell 10 minutes.
4. Pressure wash in overlapping strips at walking pace.
5. Re-sand block paving joints immediately after — before the sand can wash back out.

Common Karcher mistakes

• Blasting block paving joints out (use a surface cleaner, not a lance).
• Using the rotary tip on natural stone (leaves swirl marks).
• Pressure washing tarmac with hot water (pits the surface).
• Skipping the pre-treatment and just blasting — spreads moss spores.

When to hire a pro instead

Professional kits run 200+ bar with hot water up to 150°C — the only way to lift old oil and lichen properly. If a domestic wash didn't fix the problem, a pro wash almost certainly will.