God knows! The tradesman is the guy who did some of the work when I had the interior done, so he knows. I think he said something about needing to anchor them, so probably timber frame with plasterboard. He said I couldn't have floating shelves which is what I wanted, because they would need more support.
Depending on how much he is going to charge, I am having them on one wall in the living room and one wall in the second bedroom. I am also wanting to get a floor to ceiling climbing pole with a couple of shelves, but can't find one that also looks good.