On 18/07/2019 02:32, RJH wrote:
On 17/07/2019 18:33, The Natural Philosopher wrote:
On 17/07/2019 16:48, R D S wrote:
On 17/07/2019 15:40, newshound wrote:
Perhaps, or common or garden rising damp but held back by an
impervious plaster, or plaster over tanked brickwork?

Has rising damp not been debunked?

Everything credible that I read suggests that 'damp' comes from above
somehow.

No. rsing damp exists and I had it badly. But it doesnt rise that far
- in general if you get a foot above the water table you are unfortunate.

I thought the maximum was about 2m for rising damp? Which in part
explains why it's one of the most misdiagnosed causes of damp to
internal walls.

The OP's looks like condensation/cold bridging to me.

that is what I originally thought.....