Concrete Cleaning & Graffiti Removal

Concrete is the surface we clean most often, largely because it's what the region's least-loved spaces are made of. Subways, car park decks, underpasses, service yards, the backs of retail units, the undersides of bridges — the places that attract graffiti, fly-tipping and neglect are overwhelmingly concrete.

The good news is that concrete is tough and takes a proper clean. The catch is that it's far more porous than its solid appearance suggests, so contamination goes in rather than sitting on top, and the rougher the finish the deeper it goes.

Finish matters more than you'd think

Two concrete surfaces can behave completely differently depending on how they were finished. A power-floated deck is dense and comparatively smooth, so aerosol sits close to the surface and generally comes off well. A brush-finished or tamped surface, or anything where the aggregate is exposed, is a mass of tiny reservoirs — pigment lodges in every one, and getting it all back out is much harder.

Shuttered concrete on a subway wall or bridge abutment often carries the grain of the formwork plus a layer of laitance, and behaves differently again. Aged concrete that has carbonated and started to break down at the surface is more absorbent still.

This is why we don't quote graffiti removal on concrete from a description. A photograph showing the surface texture tells us more about how the job will go than the size of the tag does.

Car park decks and hard standing

Decks and yards are a different job from vertical concrete. The contamination is traffic film, tyre rubber, oil drips, silt and general grime, spread evenly over a large area — which is exactly what rotary jetting is designed for.

We use a shrouded rotary surface cleaner rather than a hand lance on anything large. It holds a constant height and speed so the coverage is even, with no lance stripes left behind when it dries, and it keeps water and debris contained instead of spraying it over parked cars. Hand lances then take care of the edges, kerb lines, bollards, drainage channels and the corners the rotary can't reach.

Oil is the one that needs care. Jetting a greasy patch without treating it first spreads the oil over a wider area and leaves a bigger, fainter stain than you started with. Grease needs an alkaline degreaser, dwell time, then a rinse — and where it has soaked into the slab over years, a poultice to draw it back out.

Run-off is part of the job

Water coming off a car park deck or service yard carries oil, rubber and silt with it, and on most sites the gullies are surface water drains that discharge to a watercourse. Letting that run-off go untreated into them is a pollution offence, not just poor practice.

We plan it before we start: where the falls run, which drains are foul and which are surface water, whether the site has an interceptor and whether it's been maintained. Depending on the answer we bund, mat, divert or vacuum-recover. Around Greater Manchester a great many surface water systems discharge to the canal network or the Irwell and Mersey catchments, so it genuinely matters.

Subways and underpasses

Underpasses are their own category. They're sheltered, poorly lit, unobserved and usually concrete on every surface — close to ideal conditions for both graffiti and organic growth, and often carrying an ingrained smell from years of use.

The work is rarely just removal. A subway clean typically means graffiti removal, a full wash-down of walls, soffit and deck, degreasing where needed, drainage channels cleared and sanitising treatment. The atmosphere is enclosed, which affects which products can be used safely, and lighting and ventilation are usually poor. Our subway and underpass cleaning page covers how we approach them.

For structures that get repeatedly hit, an anti-graffiti coating on the wall surfaces changes the maintenance economics completely — cleaning drops from a specialist visit to a hot-water wash-down that a routine crew can do.

What concrete won't come back from

Being straight about limits: cleaning removes what's on and in the surface, but it can't reverse changes to the concrete itself.

Long-standing oil contamination may leave a permanent shadow because it has migrated deep into the slab. Acid damage or previous aggressive jetting that has exposed the aggregate has permanently changed the texture, and cleaning it just gives you clean rough concrete. Carbonated, spalling concrete with corroding reinforcement showing needs a concrete repair specialist, not a cleaner — though we'll photograph and flag it for you if we see it, because it's the sort of thing that's cheaper to catch early.

Patch repairs in different mixes will still read as patches once everything is clean. Where that matters aesthetically, an anti-carbonation or decorative coating over the cleaned surface is the usual answer.