my new extension needs to have the floor compleated,,, up to now it as mot,,visqeen,, 4 inch kingspan,, then 6 inch of conceat all passed by building control,, i now need to finish it by bringing it up approx 3 inch which i can by boarding it over with ply or chipboard ,,, can i do this ,,, or do i need to create ventilation ???? between the concreat and the ply
