Can someone advise WHY you need to plaster a wall and what happens if you don't ? Is it possible to paint directly onto an unplastered wall ? If so what preparation does the surface need ?
generally done to provide a better finished appearance.Lots of examples of brick walls painted with emulsion/masonary/gloss paints.Remove any loose material (wire brush) make sure its dry if using oil based paints.Possibly prime with diluted emulsion if using gloss paint.
If you ever want to paper a brick, stone, or breezeblock wall, it's better if it's been plastered. Otherwise, the paper turns out lumpy. (And you'll never get a good butt-joint)!