About 15 years ago we had work done in the kitchen, this necessitated a new supporting column / pillar being built up. Over the last few years the plaster on this has bubbled and blistered, even the angle bead appears to rust up the wall. Now it’s got really bad and lumps of plaster are dropping off. The builder who did the work is a no go, too many problems. Another builder tried to fix it a few years back by cutting a gap to prevent bridging or capillary action but that does not seem to have worked. Am I looking at having the whole thing ripped down and re-built? Any thoughts?

Probably an ineffective damp-proof course or ‘bridging’ that’s allowing water ingress. Speak to a damp-proof specialist – probably requires the damp plaster to be chopped out and maybe an injected DPC into the brickwork rather than replacing it all.

Probably a combination of things, it appears salts are present, I’d say ingress and high humidity.
How old is the property, was the wall built straight onto the floor, is that an external door, if it is how high is the outside ground level? Got pics of the other side?

Kitchen? Is there decent ventilation?

If its rising damp you can buy the injector stuff at a reasonable cost and do it yourself. I did by our door into the kitchen and an area in the dining room. 4 years later and its dry as a bone.

Thanks all for the replies, much appreciated.

I would say the kitchen has decent ventilation and this is the only damp issue in the entire house. The rest of the kitchen has never had any damp on the walls or issues in the past. Indeed the wall the pillar is against is fine.
The house is Victorian, typical mid-terrace, but the pillar is all new, apart from maybe the external face of it. iirc it was built onto new footings as when the kitchen was being done up it was apparent the Victorian builders hadn’t bothered with foundations and the rear of the house was being held up by an outside toilet. The pillar was put in to support a steel for a new open plan bit of the kitchen.

The outside surface, all paved, is about five inches below the kitchen floor.

@twinw4ll Do you mean the other side as in outside or the other internal side of the pillar? To start, the other side internally of the pillar was worse and the angle bead hard rusted etc, but after the last attempt at a fix that is a bit better but not 100%- bit of bubbling and again the angle bead is looking rough.

The fact that it’s got worse during one of the wettest autumn/winters on record suggests it’s ingress from the outside, possibly made worse by wind pressure.

Diffcult to say more without understanding how it’s joined to the exterior wall.