Hi, I have had a new stair fitted which left a large whole in the wall. I have plasterboarded this however, eventhough the plasterboard is plumb the wall isn't and part of the plasterboard is about 3 - 4mm from the wall. There is also some brick showing and the wall doesn't appear to run at 90 degrees but tapers off as it reaches the ceiling. Would it be best to render the wall (sand / cement / lime) to creat a flat surface for skimmimg and should I PVA the whole wall, and plasterboard prior to starting? Also, what is the advantage of the sand/cement/lime over browning - if any! Thanks