'fibro' refers to asbestos fibre cenent sheeting - used on the outside, wet areas inside, and sometimes all the internal walls too, during a certain period. It was perhaps the cheapest cladding material.

'fibro' no longer is allowed to contain asbestos, but a similar product is still available. There is much pressure to have it removed appropriately from houses - many roofs also had a similar substance that looks like corrugated roofing iron.