What an insurer has to establish, and what it does not
A gradual damage refusal is usually two claims in one letter. The first is that the damage developed over time. The second, often unstated, is that you should have noticed. The published decisions treat those as separate questions, and the second one is where most overturned refusals fall.
The evidential standard is worth knowing before you read any of this. DRN-5646463 puts it plainly: an insurer "only needs to show on balance of probabilities that the damage was likely to have occurred gradually. It does not need to definitively show this was the case." So the first question is rarely won by arguing that the insurer cannot prove it. The second one is different.
DRN-3789370: black marks on a skirting board
In March 2022 a policyholder noticed black marks on the skirting board of a utility room and wiped them away. They came back a few days later. Peeling back the wallpaper revealed damp underneath, and the insurer was contacted at that point. AA Underwriting told the policyholder to instruct a plumber or builder to carry out trace and access. The tradesman lifted floor tiles, found a burst pipe and repaired it.
AA’s surveyor then attended and reported damp on the walls, with photographs, and mould spread across walls and a door frame. Because the leak was under the floor tiles, AA concluded this was not a one-off event but had happened gradually, and it declined both the water damage and the trace and access damage.
The wording covered escape of water and, notably, said the insurer would "pay up to £5,000 in total for the costs we have agreed in advance for locating the source of the damage including the reinstatement of any wall, flooring or ceiling removed or damaged during the search". The general exceptions excluded "loss or damage arising from gradually operating causes including deterioration, wear and tear, corrosion, rot or similar causes".
The complaint was upheld. Three things did it.
- The insurer stated the test against itself. AA’s own final response quoted the service’s approach, accepting that where a claim is repudiated under a gradually operating clause the insurer must also show the policyholder would have been reasonably aware of the damage occurring.
- The location did the arguing. The Ombudsman recorded that AA had itself recognised the leak was underneath floor tiling, and found that as the leak was under the floor, damage would not have been immediately obvious.
- The sequence held up. The account of noticing marks, wiping them, seeing them return, lifting the wallpaper and calling the insurer was accepted, and the report from AA’s own surveyor described that same sequence back to it.
The Ombudsman called it a finely balanced judgment, because the peeling wallpaper and the damp behind it would have become increasingly noticeable. It still went the policyholder’s way, and AA was directed to carry out the repairs and drying and to pay £150 in compensation for the delay and for six months of exposed floor pipes.
DRN-5970477: the photograph that only existed after demolition
The second overturned refusal is the shower case covered in more detail in two shower leaks, two decisions. What matters here is which piece of evidence moved it.
Advantage relied on a leak detection report and a surveyor’s report, both of which pointed at failed shower seals. The policyholder’s counter-evidence was a plumber’s statement written seven or eight months after the inspection, with no photographs and no testing, and the insurer said so in terms.
The Ombudsman agreed the statement was weak, and upheld the complaint anyway, on photographs taken after the shower was dismantled. Those showed a heavily corroded valve bracket behind the tiles and rotten wood below it, with timber damage above sealant level. The insurer’s own site dictation had mentioned water dripping from the shower valve and rust staining on it. Put together, that made a concealed pipework leak the more likely predominant cause and pushed the sealant defect into second place.
The decision also criticised the agent’s report for omitting the cause of damage entirely, leaving two sentences reading "the damage was caused by" and nothing after. The insurer explained that its supplier’s system does not always populate that field. Worth remembering that the report your insurer is relying on can be defective, and that it is reasonable to ask to see it.
DRN-5646463: where it did not work
The same exclusion held in DRN-5646463, and the contrast is instructive because the loss was more dramatic, not less. A bath would not drain, the waste pipe below leaked, and the kitchen ceiling partially collapsed before a plumber arrived.
A CCTV drainage survey found a broken bend, two large displaced joints and a blockage caused by an old bottle. The specialist thought the displacements would have taken more than twelve months to reach that size and that the drains would have blocked several times before the claim. The loss adjuster photographed mould in the kitchen and deteriorating grout with moisture behind the bathroom tiles.
The Ombudsman worked through both limbs. The insurer had shown gradual cause on the balance of probabilities. And on knowledge, the mould in the photographs was not minor, sat high on the wall close to the ceiling beneath the bathroom, and the exterior of a pipe was visibly heavily corroded. The policyholder’s explanation that the mould came from a cold room and a kettle did not survive the photographs.
The pattern, stated plainly
| Decision | Where the leak was | What the visible signs were | Outcome |
|---|
| DRN-3789370 | Under floor tiles | Black marks on a skirting board, then peeling wallpaper | Upheld |
| DRN-5970477 | Behind bathroom tiles | Damp on a wall below, checked by a plumber who found nothing | Upheld |
| DRN-5646463 | Underground drainage | Extensive mould high on a kitchen wall, corroded pipe, repeated blockages | Not upheld |
The overturned refusals share a shape. The defect was physically inaccessible, the early symptoms were ambiguous, and the policyholder had done something about them before the serious damage appeared. The refusal that held involved symptoms that were neither ambiguous nor hidden.
What to keep, if you keep anything
The evidence that decided these cases was mostly created before anyone was thinking about a complaint. Dated photographs of the symptom at the point you first saw it. The name and date of the first tradesman who looked at it and what they said. Photographs of the concealed pipework once it is exposed and before it is covered again. Moisture readings with locations attached rather than a bare number.
That last one is the part we control. Our detection report records method, readings, location and the reason the building had to be opened where it was, because the arguments above are all arguments about a record nobody kept. The underlying exclusion is set out on the gradual damage page, and the reasons claims fail more broadly on why water leak claims get declined.
Read this properly
These decisions were reached on the policies and the evidence in front of the Ombudsman in each case. They are not precedent, they do not bind your insurer, and nothing here says your claim will succeed. If you want a refusal reviewed, get a written final response naming the clause, then refer it to the Financial Ombudsman Service, which is free and has six months from the date of that response.
When not to call us
If your insurer has already accepted the claim and appointed its own detection contractor, let them run it. Bringing in a second firm at your own cost rarely improves the outcome and can complicate the file. Call us when the leak has not been found, when the report you have been given does not say where the water came from, or when nobody has looked behind the thing the water is running down. £150 per hour, agreed before we attend, and no charge for the search if we do not find it.
