You cleaned the whole space and a fine grey film returned within two days. That is not a cleaning failure — it is physics, and it has a method.
It is one of the most common frustrations after a renovation. The contractors finish, you clean the entire space thoroughly, and two days later a fine grey film has settled over everything again. Nothing was done wrong. The dust was simply still in the air when you cleaned it off the surfaces.
Drywall dust behaves differently
Sanding joint compound produces particles far finer and lighter than ordinary household dust. They stay suspended in the air for hours — sometimes days in a sealed space with no ventilation — and they settle gradually rather than all at once. Clean the surfaces while that cloud is still aloft and you are cleaning ahead of the dust, not after it.
Those particles also get into places ordinary dust does not: window tracks, the tops of door frames, inside vent louvres, behind outlet plates, into carpet fibre and along every horizontal edge in the building.
The staged method
Professional post-construction cleaning is done in stages for exactly this reason. First, a rough clean: all debris, offcuts, packaging and protective sheeting removed from the space. Second, a full surface clean working strictly top to bottom, so anything dislodged from high surfaces falls onto areas not yet cleaned.
Then — and this is the step almost everyone skips — you wait. Ventilate the space, run air movers if you have them, and let the remaining airborne particles settle. Only then do you return for the third stage: the final detail pass across glass, fixtures, tracks and floors.
Vacuum before you wipe, always
Wiping a dusty surface with a damp cloth turns fine dust into a smear that bonds to the finish and is much harder to remove. Vacuum surfaces first with a brush attachment, then wipe. On glass, dry-dust before any liquid touches it — otherwise you are grinding grit across the pane.
Do not forget the systems
If the HVAC ran during construction, dust is in the ducts and the filters, and it will redistribute through the building every time the system cycles. Replace filters before handover. Clean vent covers and returns. Otherwise the cleanest room in the property will be re-dusted by its own ventilation within a week.