After the water has gone, the hard part starts. Most homeowners are told "a few days" and are then still living with dehumidifiers six weeks later, which is disheartening when nobody has explained why. Here is an honest breakdown of what actually takes time when a house dries out, and what you can reasonably expect.
For a typical flooded ground floor in a Victorian or Edwardian terrace, expect structural drying to take somewhere between three and twelve weeks. A contained escape of water from a burst pipe onto a modern floating floor might be done in seven to ten days. A river or surface water flood that has sat in solid floors and sub-floor voids for two days can run to three or four months before readings are stable.
The variable that matters most is not how much water came in, but what it soaked into and for how long. Water sitting for six hours behaves very differently from water sitting for two days, because absorption into plaster, screed and timber is time dependent. That is why the first 48 hours are worth far more than any amount of equipment later.
Drying is not one process. Understanding the stages helps you judge whether progress is normal or whether something has stalled.
Around Balham, Tooting and Clapham, most of what we work on is late Victorian terraced and semi detached property, often converted into flats. Solid nine inch brick walls with lime or gypsum plaster hold a lot of water and release it slowly. Suspended timber floors over a ventilated void are usually good news, because air can be moved through them, but if the void has filled with water and the airbricks are blocked or have been rendered over, that void becomes a reservoir.
Basement and lower ground floor flats are the slowest of all. They frequently have tanking or a cavity drain membrane, and water trapped behind a membrane will not dry through it. In those cases part of the system usually has to come off, which adds time but is unavoidable.
Cold weather works against you too. Dehumidifiers need warmth to be efficient, so a January flood in an unheated property dries more slowly than the same damage in June. If you are still living there, keeping the heating on a low constant setting helps more than short hot bursts.
Dry does not mean dry to the touch. It means the moisture content of the materials has returned to a normal level for that building, measured against an unaffected area of the same construction as a benchmark. For plaster and masonry this is usually assessed with a protimeter using deep wall probes or by taking readings at depth, not just off the surface.
Ask for the readings. A reputable firm will log them weekly and show you the trend. If readings have flatlined for two weeks and are still above target, the equipment placement or the strip out is wrong, and something needs to change rather than simply waiting longer. If anyone offers to plaster over walls that still read high, that is a decision that costs far more to undo later.
Drying equipment hire typically runs to a few hundred pounds a week for a domestic ground floor, depending on how many units are needed, plus the electricity, which is worth knowing about because it usually shows on your meter rather than the contractor's. Most home insurance policies cover drying and reinstatement under escape of water or flood, and many will contribute towards the running costs, so keep your meter readings from before and during.
Total job cost depends entirely on the extent of strip out and reinstatement, so treat any figure quoted before the walls are opened up as provisional. What we would advise is to get the drying started immediately, even before the claim is fully agreed. Insurers expect you to mitigate further damage, and every day of delay adds disproportionately to the eventual timeline.
Only when the outside air is drier than the inside air, which in a British autumn or winter it often is not. Once dehumidifiers are running the property should be closed up, because open windows simply pull damp air in and make the equipment work against you.
Many people stay if the damage is confined to one area and the kitchen and bathroom are usable, though the noise and heat from drying equipment is genuinely wearing. If the flood involved sewage, affected the electrics, or covers most of the ground floor, alternative accommodation is usually the sensible option and is often covered by your policy.
As moisture moves out of masonry it carries dissolved salts to the surface, which show as white bloom or damp looking patches even when the wall is dry. This is normal, but it means affected plaster usually needs hacking off and replacing with a salt retardant render rather than just being painted over.
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