floor to wall, gap or no gap

[Wasted]

I am replacing some timber floor boards in a ground floor flat which which have started to rot where they have been in contact with a wall which suffers from rising damp.

historically I have always been taught that there should be a gap between floorboards and wall to allow for expansions. At the same time I see whilst looking at part L guides that flooring should go hard against the wall to stop drafts including using mastic sealant.

I am looking to lift all floor boards and add rockwool insulation between joists. I will probably replace old boards with T&G chipboard. Should the floor boards be flush to wall or should there be a gap?

confused

 

[gregers]

should be a gap,if so desired to stop draughts squirt some foam along the gap line.oh and use proper flooring not sponge u like.