Ok so we'll forget the Wickes decking idea. I have read I can strengthen the existing loft joists by sister joisting, how do I bolt these to the existing joists and also do they need to then be independently supported by hangers at either end, only small room, 10 x 6 feet, and I have a wall on either side, one outside wall and one is bathroom (dormer house). I would have thought by sistering the joists this only put more pressure on the ceiling below, or would it? when I look at the bathroom floor which is the room next to loft space it would like this method has been used there and that was done by house builders in the 60's. Or must the new floor be totally indendent and not even touch ceiling joists. I am reading lots of different methods and dont know which one is best to follow. Any help greatly appreciated.