Hello . I have had my steels fitted. The height of the top of my steels are near enough flush with my existing 1st floor level. I have to put 170x50 mm joists into the steels that are 203 in height- widths vary around the property. I aim to lay 18mm chipboard as my flooring, so obviously I have to drop the height of my joists by 18mm. The joists will be in the web of the steel but by dropping them 18 mm the top won't be tightly up against the top flange. Once timber is spaces between each joist will this be ok? Thank you