Drying time is the question people ask most often before booking, and the honest answer depends far more on method than on fabric. A properly cleaned sofa comes back damp, not wet, because the machine recovers considerably more moisture than it puts in.
As a rule of thumb: upholstery three to five hours, carpet two to four, both in a normally ventilated room. With an air mover running, both drop substantially.
What makes it slower
Airflow matters more than anything else. A closed room with the door shut and no window open can double the time. Opening a window at both ends of a room to create a cross-draught is the single most effective thing you can do, and it costs nothing.
Humidity matters next. A damp, still London day in November dries slowly; a breezy day in May dries fast. Flats close to the river are measurably slower on still days, which is why air movers come as standard on those jobs.
Room position is the third factor. Lower-ground and basement rooms have the least natural airflow of any space in a house. Upstairs lounges in terraces are slower than ground-floor ones. Internal staircases with no window are the slowest of all, which is why we run an air mover at the bottom of a flight to push air up it.
Fabric thickness plays a smaller role than people expect. A thick chenille holds more water than a thin cotton, but the difference is usually under an hour — far less than the difference between a ventilated and an unventilated room.
What you can do while it dries
Open windows, and open two if you can. Leave internal doors open so air moves through. If you have a pedestal fan, point it at the furniture — it is not as effective as a professional air mover but it helps a great deal.
Keep pets and children off the furniture until it is dry to the touch. Damp fabric picks up dirt from paws and feet far more readily than dry fabric, and it is a shame to undo the work on the first evening.
Do not put throws, cushions or covers back until it is fully dry. Covering damp fabric traps moisture against it, which is the usual cause of a musty smell after cleaning.
Central heating helps only if there is ventilation too. Heating a sealed room raises the humidity and slows things down; heating a ventilated room speeds them up.
If it is still wet the next day
That is not normal, and it means too much water went in or too little came out. It matters beyond the inconvenience: prolonged dampness risks browning as soil wicks up from the foam, and in carpet it risks damp underlay and, in bad cases, odour.
Over-wetting is usually a symptom of underpowered equipment or of rushing — a proper extraction pass takes time, and the dry-passes at the end are the ones most often skipped.
If a sofa or carpet we have cleaned is still wet the following day, tell us. We will come back, and we would far rather know.