Hi,I am having loft conversion. The builder is proposing to join 2 , 9x 2 beams together on either side to span about 5m, wall to wall. in between, he wants to place 400 c/c 8 x 2 joist( about 15 on joist hangers, suspending these by maintaining 20mm gap between the ceiling below. These joist will run for a span of 13 feet and there is a load bearing wall separating two bedrooms on first floor which these joists will run over.please note that he is not touching the existing 4x 2 joist which tun across the whole loft space covering a span of 30 feet from front wall to the back. I would appreciate any advice for piece of mind. Many thanks