Hi , I'm planning on putting some decking down to cover a concrete "patio". Decking will be supported on one side on house wall on the another side on retaining wall. There is also few problems: 1) one of the decking frame (left side of the drawing) will be a base for the shed. 2) manhole And the question is what size of joist i should use? I was thinking about 100x47 (supported by two beams underneath) but am afraid of bouncing, so maybe 125x47 will be the better option, or maybe 150x47 unsupported will do the job? Thanks in advance.