Most homeowners ask this after noticing green streaks creeping across the block paving or tarmac, and the honest answer is: less often than you'd think. As a rule of thumb, a domestic driveway needs a proper pressure wash every 12 to 24 months, though that window moves depending on the surface, the amount of shade it gets, and how it's used.
The trickier question isn't frequency, it's balance: clean too rarely and algae and moss get a grip that stains permanently, clean too aggressively or too often and you strip away joint sand, wear down the surface, and open the door to weeds and frost damage. Below we break down what actually drives the timing.
The general rule: every 12-24 months for most driveways
A sunny, well-drained block paved or resin driveway in a modern estate might comfortably go two years between cleans. A shaded, north-facing tarmac or flagged drive under overhanging trees can green up again within six to nine months. Rather than fixing a date on the calendar, walk out and look: if you can see a green or black film starting on the surface, or moss establishing in the joints, that's your trigger, not the anniversary of the last clean.
Commercial forecourts and paths used daily tend to need attention more often simply because foot and vehicle traffic keeps organic matter and grime being tracked in constantly, whereas a rarely used side path can sometimes go years untouched with no real harm done.
What speeds up regrowth
Shade is the biggest factor. Driveways under trees, next to fences, or on the north side of a house stay damp longer and grow algae faster than an open, sun-exposed drive. Overhanging trees also drop sap, pollen and leaf litter that feed regrowth. Poor drainage or a driveway laid without enough fall makes standing water linger after rain, which is exactly what moss and algae need.
In the North East, prevailing damp weather and long stretches of low winter sun mean shaded driveways can green up noticeably faster than the same surface would in a drier, sunnier part of the country, so don't be surprised if your neighbour's identical drive on the sunny side of the street needs cleaning half as often as yours.
Why over-cleaning does real damage
Pressure washing more than once or twice a year, especially with a narrow turbo nozzle held too close, blasts sand out of block paving joints. Once that sand goes, the blocks lose their interlock, start rocking, and weeds move into the gaps almost immediately. On tarmac, repeated high-pressure cleaning can erode the binder at the surface, leaving it looking dull, aggregate-exposed and more porous than before.
A competent contractor uses a lower pressure with a wider fan tip, or a rotary surface cleaner set at the right height, and re-sands block paving joints after every wash. If a company is offering to jet wash your drive every three months 'to keep it looking new', that's a sales pitch working against the surface's long-term health, not for it.
Signs it's time, regardless of the calendar
Look for green or black staining across more than a small patch, moss thickening in the joints or cracks, a slippery feel underfoot when damp, or general dullness compared to when it was laid. Any of these mean it's time, whether that's eight months or two years since the last clean.
If the drive still looks essentially clean, hold off. A yearly inspection rather than a yearly clean is the more useful habit, and it costs nothing but five minutes outside with a coffee.
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