The floors give it away first. Walk into a design studio off Clerkenwell Green and the polished concrete underfoot has usually cost more than the desks standing on it. This is a district built to be looked at, and nearly everything in it is a finish somebody chose on purpose and can tell you the supplier of.

Which makes it, from a cleaning point of view, a minefield. The standard commercial routine — one spray and one mop, then on to the next floor — will do real and sometimes permanent damage in a Clerkenwell studio. The people who work here notice a scuff on the microcement before they notice the bins are full.

What makes Clerkenwell different from the City proper?

Density of design. EC1 holds one of the highest concentrations of architects and design practices anywhere in Europe, and for one week every May, during Clerkenwell Design Week, the showrooms spill out onto St John Street and Clerkenwell Green and the whole area behaves like a trade fair. The rest of the year it is studios, practices and the occasional permanent showroom, packed into former print works and clock factories around the old Booth’s gin distillery site near Turnmill Street.

The buildings themselves shape the work. Warehouse conversions come with exposed brick and services, and single-glazed Crittall windows that leak dust and cold in roughly equal measure. Floor plates run open and deep. There is nowhere discreet to keep a cleaning cupboard, so the trolley ends up parked behind a planter in full view of a client who paid an architect a good fee to think about exactly that corner.

Why the conversions complicate everything

Exposed ductwork collects dust at three metres and nobody reaches it without a tower. Reclaimed timber floors have gaps that swallow grit. Crittall frames rust if water is left sitting in the channel. The fabric of the building is part of the design here, so the parts most cleaners are trained to ignore are the parts a studio sees every day.

What are you actually cleaning in a design studio?

Finishes. Almost all of it is finishes, and most of them were chosen precisely because they look raw and untreated.

Polished or sealed concrete floors. Microcement on walls and reception desks. Oiled oak — never lacquered, always oiled, because the studio wanted the grain left open. Blackened steel on the ironmongery and the shelving, specified for its patina. Terrazzo underfoot in the smarter receptions. Birch ply more or less everywhere, because every studio fit-out since roughly 2014 has involved birch ply somewhere. Glass writing walls doing double duty as partitions. And screens: big colour-calibrated monitors that cost four figures and loathe ammonia.

Then the things that aren’t really surfaces at all. Physical models in foam-and-card and 3D print. Material sample libraries — shelves of stone, timber, metal and textile swatches that the practice guards like a small wine cellar.

The sample library problem

Leave it alone. A material library is the one place in the studio where the correct amount of cleaning is close to none. Dusting means moving samples, moving samples means a birch veneer ends up filed in the stone section, and a spray anywhere near the textile shelf is how you ruin a swatch nobody can reorder. Dust the floor in front of it and walk on.

Which surfaces punish a standard cleaning routine?

This is where studios lose finishes, and they almost always lose them to good intentions. The instinct of a cleaner handed a smart new site is to reach for the strongest bottle on the trolley and make the place gleam. In Clerkenwell that instinct is the single biggest threat in the building.

Start with the floors, because they are the most expensive thing to get wrong. Sealed concrete and microcement both want a pH-neutral cleaner and nothing else near them. An alkaline degreaser, or worse anything acidic, strips the seal, and once the seal has gone patchy you cannot spot-repair it — the whole floor comes up and goes down again. Concrete keeps score. I once saw a reception floor bloom with cloudy white patches a week after a well-meaning operative attacked a water mark with a limescale spray, and there was no route back from that without a specialist contractor and three days of closed office.

Terrazzo is worse, because people assume they understand it. It reads as bombproof, and the marble chips in it genuinely are hard — but the binder and the aggregate are calcium-based, so anything acidic etches them to a dull grey. Limescale remover, the daily shower spray somebody brought in from home: every one of them leaves a permanent matte scar. Terrazzo doesn’t forget an acid. Neutral cleaner, damp microfibre, finished.

Oiled oak is the quiet casualty, the one nobody clocks until months in. A standard all-purpose spray carries solvents and far too much water, and both are wrong for it. The solvents lift the oil out of the grain, the water raises that grain, and after a season of daily over-wetting the timber goes grey and slightly furry along its edges — at which point the studio blames the wood, when the fault was the routine all along. Damp cloth, barely, then dry it off. The oak remembers a soaking.

Glass writing walls carry their own trap, and it comes in two forms. Half of them have an anti-glare or low-iron coating that ammonia will haze over time, which rules out the blue spray sitting in every cleaning cupboard in London. The other half aren’t wipe-clean at all — they’re partitions somebody has covered in marker mid-meeting, and one helpful pass of a cloth erases a diagram the team fully intended to keep. Neutral glass cleaner, and a habit of checking whether anything on the glass is meant to survive the night.

Then blackened steel, which is where I will plant my flag. The patina is the finish. It is supposed to be uneven, supposed to darken and lighten with years of handling, and a cleaner who “brings it back” to bright metal has destroyed the precise thing that was specified and paid for.

There is a practice on Britton Street — architects, mid-sized, the sort that enters a great many competitions — that lost the ironmongery on its meeting-room doors this way. A new cleaner, a Friday night, a tin of metal polish and real pride in the job. Everything else in the office was spotless by Monday. The door handles were bright and completely wrong, and blackened steel does not go back once you have taken it back. Nobody spotted it until the Monday because nobody comes in over a competition weekend except the two people finishing the boards. That finish had taken four years to settle. One night undid it.

So here is my actual advice, and it cuts against the way the trade tends to sell itself: strip the trolley down. Fewer chemicals, not more. A studio cleaner should carry pH-neutral, clean microfibre and the discipline to leave well enough alone. The urge to add a dedicated specialist product for every surface is, more often than not, exactly how those surfaces get wrecked.

Reading a finish before you touch it

The skill is diagnostic. Knowing what a surface is before the cloth ever reaches it. Is that floor sealed or raw? Is the steel meant to be dark? Is the oak oiled or lacquered — run a fingertip, lacquer feels faintly like plastic, oil feels like wood. Whoever cleans a design studio has to answer those questions on sight, and most commercial contracts never train a single person to do it.

How do architect practices differ from the studios?

Paper. Architects still run on paper far more than outsiders expect — printed drawings pinned across the walls, plan chests stuffed with the things.

A damp cloth dragged over a desk in a design studio wipes a desk. The same cloth over an architect’s desk can wipe out a hand-marked drawing that exists in exactly one copy. The pin-up wall is live; it isn’t clutter waiting to be tidied, it is a project mid-argument. And the big plotters shed fine paper dust everywhere, which tempts an unbriefed cleaner into wet-wiping the machine — the one thing guaranteed to kill a print head. Model-making adds its own fallout: dust off the laser cutter settles on every ledge and shelf, and it wants a soft brush and a vacuum, never a damp cloth that turns it to grey paste.

There is a confidentiality dimension too. Competition entries under embargo, client work under NDA: an architect’s studio is full of material that is not to be photographed or moved, and a cleaning team that treats the pin-up wall as wallpaper becomes a genuine liability.

The out-of-hours question

Most practices want the cleaning done while the studio is empty, which sounds straightforward and isn’t. “Empty” for an architecture practice means eleven at night before a submission and dead quiet at nine the morning after it. The slot has to bend around live deadlines, not the deadlines around the slot.

What should a Clerkenwell studio put in the cleaning brief?

Specifics, surface by surface. Name the floor and its sealant. Name the finishes that must be left untouched — the blackened steel, the oiled timber, the sample library. Set the chemistry as a rule: pH-neutral by default, acids and strong alkalis simply banned from the premises. And agree what the cleaner does not go near, which in a studio is a longer list than what they do. Put a proper walk-off mat at the entrance while you are about it — the cheapest protection any of these floors will ever get is stopping Clerkenwell’s street grit at the threshold before it grinds itself into the seal.

The trolley test

Ask to see the trolley. A cleaner properly briefed for this kind of work arrives with less on it than you would expect: a bottle of pH-neutral, a stack of dry microfibre, a soft brush for the models nobody should be wiping, and nothing at all that promises to strip a floor or shine a handle.