size of improved storehouse

the size is 2x3,
but you can build on 2x2 if there are only trees on the extend 2x1 area.

http://i.imgur.com/XMu6aN2.jpg

http://i.imgur.com/OW73TMl.jpg

Is it always like that or change recently? I just notice this and start to replace several regular storehouse with improved one.

so based on this - i still cannot fit an ISH in a spot surrounded by farms and silos (in place of an old storehouse)?

It is related to this. So yes, new.