Roof insulation, compressive strength according to DIN 4108-10, Table 2

dk          no compressive load capacity, e.g. inter-rafter insulation

dm         medium compressive load capacity, e.g. unused roof surfaces

i.e          . high compressive load capacity, e.g. used roof surfaces

ds            Very high compressive load capacity, e.g. parking decks

dx           extremely high compressive load capacity, e.g. parking decks

Source: bauwion