Choosing a location for mounting the attic stairs, remember that the ladder in the unfolded form has a space in the room. Given the size of the room, one can calculate the required space for expansion. The size of holes in the ceiling should be slightly larger than the chosen staircase. Saving space between the box lid and a hole in the ceiling, will align the manhole cover.

Recommend to first install the stairs, and then make the insulation around the ceiling and floor.