This is the gable end wall of my house. We moved in about 8 years ago. The was a thin crack running down the wall of the upstairs bedroom. I cut back a little either side of the crack and filled. The crack has gradually reapeared. The crack obviously follows the motar joints of the blockwork as it steps down the wall. It doesn't continue in to the living room below. Over the last year, other hairline cracks have appeared in the wall. ( the main crack being 1 to 2mm wide). I've just also noticed a 'step' in the plaster no more than 1-2 mm betwen either side of the worst part of the crack. My question is who should I get in ? Plasters to cut back plaster and replaster or a structural engineer incase it is structural Would a plasterer let me know how serious it is?