The six stages a competent job follows
There is a published framework for this. PAS 64:2013, Mitigation and recovery of water damaged buildings. Code of practice, was published by BSI on 30 July 2013 and provides guidance on how to restore water damaged buildings from the initial incident to the point at which repair and reinstatement commence. It was withdrawn on 30 April 2026, but the process it set out is still the right shape, and it is still the clearest list of questions to put to anyone quoting to dry your property. The stages it covered were:
- Initial inspection of the water damaged building.
- Setting drying and cleaning goals, including air quality goals.
- Selecting the drying and cleaning techniques and equipment to be used.
- Monitoring the drying and cleaning progress.
- Verifying that the drying and cleaning goals have been met.
- Documentation for provision to the customer.
Notice what is in that list and what is not. There is a target, there is measurement against the target, and there is a document at the end. There is no stage where somebody decides it looks dry.
Fix the source first, and prove it
The most expensive mistake in this whole area is drying a building that is still getting wet. A dehumidifier in a room with a live pinhole in a heating pipe under the screed will run for weeks, cost a fortune in electricity, and achieve nothing measurable, because the input never stops.
So the order is: locate the leak, repair it, confirm the repair holds under pressure, and only then start drying. On a heating system that means a pressure test that holds, not a gauge that has stopped dropping for an afternoon. On a supply pipe it means the meter static over an hour with everything off. If nobody has done that before the drying equipment arrives, ask why.
The mistake that costs the most
The second most expensive mistake is reinstating too early, and it is very common because reinstating is the visible part and drying is not.
New plaster skimmed onto a wall that is still wet at depth blows within a season, because the moisture migrating out has nowhere to go. Laminate or engineered board laid over a screed that is still holding water cups and lifts at the joints. Paint over a damp ceiling blisters. In each case the repair has to be done twice, and the second time it costs more than the first because the failed work has to come off.
The only defence is a number. Ask what the target reading is, on what instrument, and at which points, before anyone starts putting the building back together.
What can be dried and what cannot
| Material | Usually dried in place | Usually replaced |
|---|
| Solid masonry wall | Yes, slowly | Rarely |
| Plaster on masonry | Yes | Where it has blown or lost its key |
| Plasterboard, briefly wetted | Often | If it has delaminated, bulged or sagged |
| Plasterboard, saturated for weeks | Rarely | Usually |
| Sand and cement screed | Yes, with targeted drying, and slowly | Rarely |
| Anhydrite or gypsum screed | Difficult, and easily damaged | Sometimes |
| Chipboard flooring | Rarely, once it has swollen | Usually |
| Engineered or solid timber flooring | Sometimes, if caught early | Once it has cupped or the veneer has lifted |
| Mineral wool insulation in a floor or wall void | No | Yes |
| Ornate plaster cornice and ceiling roses | Yes, and worth the effort | Rarely, if dried carefully |
The line that matters most in a London flat is the insulation one. Mineral wool in a floor void holds water against the joists indefinitely and will not dry in situ. If a leak has run into an insulated void, that insulation has to come out, and any quote that leaves it in place is not a drying plan.
Not all water is the same
Clean water from a burst supply pipe is a drying problem. Water from a shower waste, a washing machine or a dishwasher carries detergent, grease and organic matter, so surfaces need cleaning as well as drying. Water from a WC or a foul drain is a different category again, and materials that absorbed it are generally removed rather than cleaned, which is why PAS 64 set air quality goals alongside moisture goals rather than treating drying as purely a humidity exercise.
If the source was a drain rather than a supply pipe, it is also worth establishing who owns the pipe before anyone talks about cost. Thames Water are responsible for public sewers under roads and footpaths, and for sewers shared with neighbours even where they run under your garden or driveway, while pipes within your boundary serving only your property are yours.
How long it takes
We will not give you a figure, and you should be sceptical of anyone who gives you one before they have taken a reading. The honest answer is that it depends on the material, how deep the water went, how long it was there, the construction of the floor or wall, the time of year, and whether the void can be opened up and dried directly rather than through the surface.
What you can insist on is that the answer becomes a number quickly. After the first set of readings, a competent contractor can tell you the target, the current position and roughly how fast it is moving, and can revise that at each monitoring visit. Progress you can see on paper is the point.
Why surface readings mislead
A damp meter pressed against a wall reads the surface, and the surface is the first part to dry. That is the trap. A plastered wall or a screed floor can read comfortably dry at the face while the material 20 or 30mm in is still holding a substantial amount of water, and the moment the surface is sealed with paint, adhesive or a floor covering, that deeper moisture stops being able to leave and starts pushing outwards instead.
The way round it is to read at depth as well as at the surface, using probes set into the material or a calibrated hygrometer sealed to the floor and left to reach equilibrium, and to take those readings at the same marked points each visit so the trend is real rather than an artefact of where the meter was held. A drying record that shows the same three positions falling steadily over a fortnight is evidence. A single reading on the day somebody wants to start tiling is not.
What to ask before you let anyone start
- What is the target reading, and on what instrument is it taken?
- Where are the monitoring points, and are they marked so the same spots are read every time?
- How often will they be read, and will I get the readings?
- What happens to insulation, chipboard and any material in the affected void?
- Has the source been repaired and proved, or are we drying a live leak?
- What is the document at the end that says the goals were met?
Six questions, and they filter out most of the bad jobs before they start.
The insurance side, briefly
Drying and reinstatement are normally where the money in an escape of water claim goes, and the parts of the policy that matter are the trace and access cover and how the insurer treats gradual damage. That is a subject in its own right and we have written it up properly under insurance claims rather than compressing it here.
Who puts the building back
This is where most leak firms stop. They find the leak, they hand you a report, and the hole in your floor becomes your problem to solve with a separate builder, a separate plasterer and a separate tiler, each of whom blames the last one.
We keep handymen and builders in-house, so the same job that opened the floor closes it: screed, flooring, plaster, ceilings, tiling and decoration. Work is charged at £150 per hour, agreed before we attend, and detection carries our no find, no fee position, so if we do not find the leak you do not pay for the time spent looking. Leak damage repair and reinstatement sets out what that covers, and pricing explains how the hours are counted.
