Damp!

[ss]

Maybe already asked but is this a recent thing or has it been this way for a while? As someone already mentioned a few more clear images could help of both external and internal.

[RJH]

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.

[RJH]

Moisture that side of the wall can evaporate. On the inside, warm air hits cold wall, and the moisture in the air condenses. Ventilation may be an issue too. The spores may have got into the plaster, and that part of the wall is locked in a cycle of mould.

Possibly. In the absence of another explanation it might be worth taking it back to brick and replacing the browning/plaster with something a bit more mould inhibiting, or if there's room, dry lining that portion of the internal wall.

[tabbypurr]

Condensation is most probable, though there are other maybes. Why one side only? Probably differing insulation or bridging in the wall.

Solution? Dehumidifier.

NT

[Harry Bloomfield]

No, rising damp can still be an issue - the thing is not all damp is of the rising variety. Sometimes it is lifestyle condensation, sometimes water igngress through walls, rooves, or gutters leaking.

[www.GymRatZ.co.uk]

Frame drainage blocked so water finding it's way out via plastic welded mitre joint in corner, or tracking through a frame fixing screw or running along frame DPC until it gets to the corner? Combination of the above?

[R D S]

I wonder how prevalent it actually is?

In that I wonder how many people have stumped up for a DPC, as a ratio of those who actually needed one, After a [cough] expert has been round their gaff with one of those things with a pair of probes on it.

[Dan Green]

Sorry, you misunderstood but it's my fault having re-read what I wrote. When I said the "opposite" side of the wall I meant the mirror image as it were; the other *internal* wall side.

[John Rumm]

Not debunked as such, but it has been identified that it is far less common than the number of diagnosis of it would seem to suggest.

Also through and up are options.