One solution is to ignore the sagging factor and install what known as an attic stair insulator.
Door on attic stair is warped.
The convenience of attic stairs.
Plus if you have your air on cool air is getting up there and making the prefect storm causing your door to warp.
From inside the attic check for obstructions when the door is closed check shims installation cords to make sure nothing is interfering with the door shutting properly.
By pulling down on a string the trap door opens revealing a fold up ladder held in place by springs and hardware.
Common problems with pull down stairs.
It s essentially an insulated cover that sits on top of the attic stair area.
Brought down to the floor accessing the attic crawl space is simply a matter of climbing the ladder.
If nothing else you need to insulate around your door to prevent cool air from getting in.
Hi bill it looks like you don t have proper ventilation insulation in your attic.