Tarmac is tougher than block paving in some ways but more delicate in others, and cleaning it without damage means understanding that distinction. Pressure that's perfectly safe on concrete can chip aggregate loose from an ageing tarmac surface, especially where the binder has already started to weather and soften with age.
This guide covers safe pressure limits for tarmac, how to treat moss properly rather than just blast it, and when a restorer product is the better fix for tarmac that's lost its dark, finished look.
Safe pressure limits for tarmac
Tarmac generally tolerates moderate pressure washing well when the surface is in good condition, but older or already-weathered tarmac, where the black binder has started to grey and the stone aggregate is more exposed, is more vulnerable to having that aggregate loosened by concentrated jets.
Keep the nozzle at a wide fan angle rather than a pinpoint turbo jet, maintain reasonable distance from the surface, and avoid holding the jet in one spot. If loose stone starts coming away as you clean, that's a sign the tarmac is already past the point where pressure washing alone is the right approach, and continuing will only accelerate wear and widen any existing cracking.
Treating moss properly
Moss on tarmac, especially in shaded areas or where drainage is poor, should be treated with a biocide moss killer first, left to dwell and die back, then cleaned rather than pressure washed while still alive. Blasting live moss off without treatment leaves spores in the surface texture and cracks, meaning it typically returns within months.
This treat-then-clean order matters more on tarmac than most surfaces, since tarmac's texture gives moss plenty of grip to hide in even after a visible clean. Persistent moss along the edges of a tarmac drive, where it meets a lawn or border, is often a drainage tell-tale too, worth a look before assuming it's simply a cleaning issue.
When a restorer is the better answer
Tarmac that's gone patchy grey rather than staying uniformly black usually isn't dirty in the way that cleaning fixes, it's weathered, with the surface binder oxidising from UV exposure over years. A tarmac restorer or sealant, applied after a proper clean, replenishes that surface binder and restores the dark, uniform finish, something no amount of pressure washing on its own will achieve.
This is worth knowing before booking a clean expecting a full colour transformation on an older driveway, since a clean alone won't undo years of UV weathering. It's a common source of disappointment when a customer expects a faded, sun-bleached drive to come back jet black from a wash alone, so it's worth asking a contractor directly whether restoration is included or needs to be quoted separately.
Typical costs
Professional tarmac cleaning typically costs around £3-£5 per square metre, with moss treatment sometimes priced separately or bundled in. A tarmac restorer/sealant application on top of a clean is usually an additional cost, but is often the step that makes the biggest visible difference on an older, faded driveway.
Cracks and potholes are worth mentioning separately from cleaning, since a jet wash won't fix structural surface damage, and any significant cracking is better raised with a tarmac contractor for repair before or alongside a clean and restore visit.
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