Before you do anything else about a lease that ends this year, go and stand in the middle of your unit and look down.
Not at the walls, which will be repainted by somebody for a known price. Not at the roller shutter, which either works or gets repaired. Look at the slab, and specifically at the parts of it you have not seen in years – under the racking, behind the pallet stacks, in the strip where the forklift turns. That is where your dilapidations bill lives. In a warehouse or a light industrial unit, the floor routinely accounts for more of the final settlement than every other item on the schedule put together, and it is the one part of the building that a tenant has almost never thought about since the day they moved in.
Why does the floor decide the bill on an industrial handover?
An office hands back on the strength of its finishes. Carpet, paint, ceiling tiles, all of them replaceable at rates a surveyor can look up. An industrial unit is mostly a steel frame, a roof and a slab, and two of those three are not yours to damage.
The slab is. It is the only surface in the building that takes the entire weight of your operation for the whole of the term, and unlike everything else it cannot be swapped out at the end for a few thousand pounds. A slab that has been abused reads as abused, and a surveyor pricing the remedy is pricing either a specialist clean, a resin coating over the top or, at the far end, sections cut out and recast. Those are three very different numbers and the difference between them is decided by what you did in years one and two, not by what you do in the final fortnight.
Nobody in the trade puts it this way, so I will. The slab remembers.
What a surveyor does in the first ninety seconds
They walk the aisles. Not the perimeter, the aisles, because that is where the traffic ran.
Then they look for four things. Dark patching under where machinery or a delivery bay sat. Black arcs and scuffs at the turning points. Pale rectangular shadows where racking uprights stood. And joints – the sawn or formed lines across the slab – checked for spalling at the edges, which is the crumbling you get when hard forklift wheels have hammered an unsealed joint for a decade.
Ninety seconds gets them to a category. Cleanable, coatable, or structural. Everything that follows in the schedule is a refinement of that first judgement, and the tenant who has never looked at their own floor with those four questions in mind arrives at the negotiation with no idea what category they are in.
What happens to a concrete slab over a ten-year tenancy?
Industrial slabs in London are usually power-floated concrete, laid smooth and left bare. Bare is the operative word. A power-floated finish looks sealed and is nothing of the sort: it is a dense but porous surface with an open capillary structure, and everything liquid that lands on it starts moving downwards.
Untreated concrete also dusts. Traffic abrades the surface paste, which is why a busy warehouse develops that fine grey film on every low shelf, and the dusting itself opens the pores further. A slab five years into heavy use is thirstier than the same slab on day one.
Then there is the loading. Point loads from racking legs, dynamic loads from a laden forklift crossing a joint at speed, chemical attack from whatever your operation spills. All of it accumulates, none of it reverses.
Oil is not a stain on the floor, it is inside it
This is the part tenants find hardest to accept, and I have had the conversation in a dozen units. Engine oil, hydraulic fluid and gearbox oil that has sat on unsealed concrete for years has wicked down into the slab, in some cases twenty or thirty millimetres.
Nothing applied to the surface reaches that. A degreaser lifts what is in the top couple of millimetres and the rest sits below, and within a fortnight it migrates back up and the stain reappears, paler and softer at the edges. A poultice does better, because it draws by capillary action as it dries rather than working downwards, and repeated poultice applications will pull a surprising amount out of a slab. What they will not do is deliver a floor with no history.
A tenant who ran a fabrication business or a fleet workshop needs to know this before they buy anybody’s remediation quote. The honest ceiling on cleaning a deeply oiled slab is a substantial improvement and a visible ghost. Any contractor promising better than that is either coating over the top or has not seen the floor.
Which marks come off, and which ones never will?
Sort the floor into categories before you price a thing.
Rubber transfer from forklift tyres comes off. It looks alarming – long black arcs that read as burns – and it is polymer deposited on the surface, not damage to it. The right rubber-mark remover and a rotary with the correct pad will take it. Using the wrong pad, which is the common error, burnishes it into the surface and makes it permanent.
Surface grime, the general grey of a decade, comes off with a scrubber-drier and the right detergent. Line marking comes off, though epoxy aisle lines need mechanical removal and that means grinding, which changes the texture of the concrete under the paint and leaves its own shadow.
Efflorescence, the white bloom you get where moisture has moved through the slab, is a symptom rather than a mark, and cleaning it without addressing the moisture achieves nothing. Spalled joints and cracks are not cleaning at all. They are repair, they belong to a different trade, and they belong in a different section of the schedule. The slab remembers, and it distinguishes between what you spilled on it and what you did to it.
The racking shadow nobody can remove
Racking is the one that catches everybody. Bolted-down uprights sit in place for the whole term, and the floor beneath them stays clean and unabraded while everything around it wears and greys. Take the racking out and you get a grid of pale rectangles across the unit, sharper than any stain.
There is no cleaning solution to this. The rest of the floor is worn and the protected patches are not, so the only route to an even appearance is bringing the whole slab back to a consistent state, which means grinding or coating the lot. That is a five-figure job in a mid-size unit, and it starts as an aesthetic complaint about some pale squares.
The fixing holes are separate again, and they are a making-good item under most yield-up clauses.
What does it cost to put right, and what would it have cost to prevent?
Rough figures on an 18,000 square foot unit, which is about 1,670 square metres.
A thorough industrial floor clean – degrease, scrub, rubber removal, several passes – runs to something in the region of £8,000 to £15,000 depending on how bad the contamination is and how much of it needs poulticing. A resin or epoxy coating over the whole slab, which is what gets specified when cleaning cannot deliver an acceptable appearance, sits nearer £60,000 to £100,000 once you include preparation. Cutting out and recasting damaged bays is priced by the square metre and by the misery.
The sealing job in week one
Sealing that slab when you moved in would have cost you a fraction of any of those numbers. A lithium silicate densifier with a decent penetrating sealer over a floor that size is a job of a few days and a few thousand pounds, applied to clean bare concrete before a single pallet lands on it.
The densifier reacts with free lime in the concrete and hardens the surface, cutting the dusting. The sealer closes the pores, so oil sits on top and gets mopped up rather than travelling down. A sealed slab still marks and still wears. What it does not do is absorb ten years of hydraulic fluid into its capillary structure, and that single difference is most of the gap between a five-figure handover and a six-figure one.
Almost nobody does it, because week one of a new tenancy is chaos and the slab looks fine.
Should you clean the floor at all before you hand it back?
Sometimes the answer is no, and I will say so on site even though it costs me the work.
If the slab is deeply oiled across a large area, spending £14,000 on remediation that leaves a visible ghost buys you very little ground in the negotiation. The surveyor still marks it up, and you have paid twice. In those cases the sensible move is a proper condition survey, a photographic record, a specialist opinion on what is achievable, and a negotiated cash settlement based on the diminution in value rather than a cleaning invoice. I have told clients in Barking to keep their money and instruct a building surveyor instead. The slab remembers, and no amount of my invoicing changes what it remembers.
Where cleaning does pay is the middle ground – surface grime, rubber, localised staining, the units where the floor is tired rather than saturated. That is most units, and there the money works hard.
February is the worst month to find out
Cold is the practical trap on a winter handover. Most degreasers and poultice systems need the substrate above about five degrees to work properly, and an unheated warehouse off River Road in Barking, IG11, in the last week of February is not above five degrees. Resin coatings are worse: below their minimum cure temperature they either skin badly or fail to cure at all.
So the March lease expiry has to be planned in January, with heaters hired and a slab warmed for a day before anything is applied. A tenant who rings a contractor in the final fortnight of a winter term will be told either that it cannot be done properly or that it can – and the second answer is the one to worry about.
