I recently moved to an 1890s mid-terrace. The external wall of our rear extension shows signs of damp and salt deposit at a height of around 1m in a wall that was recently replastered. The research I'm doing suggests this is penetrating damp. There is no visible sign of wall damage from the outside, other than a general deterioration of the surface of the original brickwork, or of a specific place where ingress could be occurring, so I am considering a salt neutraliser and then painting Ultra Proof outside. Does this sound a reasonable diagnosis and course of action?
Thanks!