Is this damp?

[LBalf]

My parents have these patches all over their walls. The house is old but only about 150 years. They completed renovated (back to brick) around 5 years ago including replastering.

Anyone got any idea.what kind of damp it is and how to sort it?

*During winter they have the Woodburner on most evenings and have the thermostat set at 18.

I'm no expert but I have lived in a lot of damp houses and yes, this looks like salt deposits pushing through?

Have they checked gutters/ pointing/air bricks?

What is on the other side?

It does look like damp.

The only damp I’ve had that went like this (rather than mould or wet looking patches) was when a ground level drainage channel running next to an outside wall was completely blocked with soil.

Yes it looks like water wicking up from below. Not a leaky washing machine or dishwasher is it?

It's impossible to tell from a photo. Is this an internal wall? And is it just at the bottom of the wall? And only this wall? If so then probably rising damp caused by a leak under the house or a breach or break in the damp course. If its all the way up the wall the leak could be upstairs. If it's an external wall it could need repointing, or it could be a leaky window frame or gutter. Or if ground level a regularly blocked drain.

In one house we has a burst water pipe cause this and in another piles of old plaster left in the crawl space under the floor boards was breaching the damp course. In that house we also had penetrative damp from a broken gutter on an exterior wall and also from broken roof tiles.

If it's 'all over' I assume it can't be a direct leak.
What sort of plaster is it? Lime or gypsum? And what sort of paint did they use? (Clay or bog standard emulsion).
I'd agree to check the underfloor vents, if any. But that looks very severe for that to be the cause.
I;d assume no cavity in the walls at that age. What's going on on the outside of the wall? Bare brick? Painted brick or render? What sort of paint and/or render? (Again lime, or cement, or what)
Was the wall at all damp when plastered? Had it been very damp before they took it back to brick?

Hi, thank you for your replies. The white walls are internal, and the same peeling patches are on other internal walls too, nearly all.of them. It doesn't go all the way up and is mostly toward the base of the walls.

The green wall is an exterior wall.
There was damp when they took over the property and had a damp proof course installed.

No idea what paint they used, perhaps it's damp trapped by non breathable paint?

How old is the house?

There are some great groups on FB for old houses and their many issues. Was it replastered in gypsum and then painted in normal paint? If so, my feeling is this is probably condensation. Old houses need to breathe. Always worth checking gutters as water can migrate from almost anywhere but my money is on gypsum and plastic paint,

Also worth checking external ground levels. If they are higher than the dpc that could also be an issue. Loo up My Old House ok FB. Lots of great advice there