7°C, brisk W, white cloud to start a nice day

A familiar route to the machines.
Decoration.
Two panels are faulty in the hall walls.

The plaster has failed because of damp. looks like rising damp which is odd because the surveyor said condensation was the cause. The walls are inside the porch so protected from the weather. The surveyor suggested it may be a eased by better ventilation in the porch. To further add to the mystery, why is the side that receives the most sunshine also the most damp?
The two walls either side of the door are slightly detached with powdery plaster under the skim. I shall probably remove the plaster down to brick. Before re-plastering, I can paint a waterproof layer directly onto the bricks. But should I? Could the moisture barrier make the problem worse?