Thinking about garage conversertion to use one end as an office, the other as utility room, it's integral garage with double skin outer wall, built in 2003. Wondering about the flooring joists to bring the height up, the dimensions are 550cm x 250cm, thinking joists width ways ? At 40 centres ? Using 4.7 x 17.0 joists ? And Kingspan k103 9.0 for insulation ? 18mm chipboard before laminate flooring ? Does this sound right ? How many joists will I require ?