They have laid hardboard sheets down over the wooden joists to form a floor.Click to expand... Define hardboard sheets in a little more detail. Floor boards are basically a thing of the past whereas plywood sheets or OSB (oriented strand board) sheets are more contemporary for subfloor use. If hardboard sheets means Masonite-type sheets I'm not sure that material is acceptable by any of the building codes these days. Never has been to my knowledge. That type of sheet-goods is used for an underlayment material in some places but never used for a subfloor. This is a little confusing... If you are at the flooring stage of the project then how were the walls built if not built on top of a subfloor? A little more information would be helpful.

Thanks for your answer. The flooring material is probably chipboard. Sorry for the confusion, I'm not au fait with flooring/building stuff. As for the floor stage comment. They've built the brickwork for the new garage, utility room and bedroom above, put joists in and now have lain the chipboard material over the joists in sheets, nailed it to the joists and glued it together. Just checking this is a good method as haven't seen it used before? Thanks