As there are stairs to get to the loft room, what is underneath?

Just empty space I think.

its a secret hideout for the knome people of course!!! i mean what if the housemates abuse them then they wouldnt have anywhere to go if there was nothing underneath

So there could be a hidden room?

Perhaps! I rekon there's one to the left of the Diary room door.

The diary room is in there. Its big and seems to expand behind the entire mirror area. No room for a hidden area.

I noticed that when makosi went in earlier to get new batteries, she seemed to open the door and go to the left whereas the chair is to the right so maybe the diary room is just bigger than it looks.

^Must be..