Month: January 2026

You do not sign it off before the air conditioning has been commissioned. That is the whole article, and everything below is the argument for it.

The pattern is the same on every Cat B fit-out I have worked on in fifteen years. The main contractor is chasing practical completion, the client’s project manager wants a walk round on the Thursday, and the cleaning contractor is asked to have the floor sparkling by Wednesday night. Then the mechanical subcontractor runs the fan coil units up to full speed on the Friday for air balancing, and eleven weeks of construction dust comes out of the ceiling void and settles across 8,000 square feet of new desking.

Everybody blames the cleaners. The cleaners were there on Wednesday and the floor was immaculate on Wednesday.

What is the difference between a builders clean and a sparkle clean?

Three stages, and most fit-out programmes budget for two of them.

The first clean, sometimes called the rough clean or the builders clean proper, happens when the wet trades are finished and before decoration and floor finishes go down. It is heavy work: debris removal, plaster and screed residue, adhesive spots, silicone off glass, wet vacuuming of the slab or the raised floor panels. Nobody photographs this stage and nobody appreciates it, which is a shame, because a floor that gets a proper first clean needs a third less time at the end.

The second clean sits after the finishing trades and before commissioning. Cores, WCs, tea points, ironmongery, the top faces of everything.

The sparkle is the final pass. Glass both faces, all horizontal surfaces, floor finish machined or buffed as specified, ironmongery polished, then the floor is closed. The word “sparkle” has become a bit of a con in this trade, because it gets sold as a distinct high-value service when most of what it contains is a second clean done properly, with better lighting and more time. If you are being quoted a large number for a sparkle on a floor that never had a first clean, you are paying twice for the same soil.

Where does the money go?

Glass and edges. Not open floor. On a typical Paddington Basin floorplate with a full-height glazed perimeter and internal glazed offices, the glazing is somewhere near two-thirds of the labour hours, and the recessed detail – shadow gaps, skirting reveals, the underside of raised floor cut edges around trunking – takes most of the rest. Open carpet is quick. It is the last thing to worry about and the first thing everyone looks at.

Why does the floor look filthy again the morning after commissioning?

Because the ceiling void was never in anybody’s scope.

Above the tiles on a Cat B floor you have cable tray, containment, fan coil units, flexible ductwork, sprinkler pipework and the sound attenuation. All of it was installed over months by trades cutting plasterboard, drilling concrete, and dropping fixings. The void is a shelf. It holds cement dust, gypsum fines, cable sheathing swarf, insulation fibres, and the fine grey material that settles out of a construction environment and behaves like talc.

The tiles go in. The floor gets cleaned. The void stays as it is, and everybody forgets it exists because they cannot see it.

Then commissioning happens. Fan coil units run up, air is balanced through the grilles, and the void goes from static to moving air. On a plenum ceiling, where the void itself is the return air path, the effect is dramatic. Dust that has sat undisturbed since March comes down through the supply diffusers in a fine grey film across the meeting room tables, the monitor screens and the carpet under the perimeter. It comes back down.

I have seen a floor off Sheldon Square go from a signed sparkle sheet to visibly soiled in the six hours it took to balance the system. The client walked in on Monday convinced they had been sold a clean that never happened.

What should be done above the ceiling, and when?

Void cleaning before the tiles are laid in, as a scheduled item with its own line in the programme.

Vacuum the tray tops and the containment with a filtered vacuum rather than blowing anything through with compressed air, which relocates the problem into the next bay. Wipe the top surfaces of the fan coil unit casings. Clear the drip trays and the condensate pans of debris, which matters for a reason beyond cleanliness, since a fixing screw sitting in a pan will block a drain and put water through a new ceiling tile in August.

If the tiles are already in and commissioning has not run, lifting a percentage of them for spot cleaning of the worst areas costs a fraction of cleaning a whole finished floor twice. Ask for that. Most main contractors will agree to it once you show them the alternative.

When should the protective film come off the glazing?

Earlier than it does. Almost always earlier than it does.

Protective film on glass, and on the powder-coated aluminium of frames and reveals, is applied at the factory or on delivery and is designed as short-term protection. Most manufacturers specify removal inside 30 to 90 days. What happens on a slow-running fit-out is that the film goes on in November, the programme slips twice, and by the time anyone touches it the glass has had five months of direct sun through a south-facing elevation.

Ultraviolet cures the adhesive. The film goes brittle, tears into strips instead of peeling in a sheet, and leaves a continuous adhesive residue bonded to the surface. On glass that is recoverable with solvent and patience and a lot of hours. On coated glass and on polyester powder-coated frames it is a different problem, because the solvents that shift cured acrylic adhesive will also attack the coating, and a blade that removes residue from float glass will scratch a soft coat or a self-cleaning surface permanently.

The cost differential is not subtle.…