内側 and 外側: inside and outside a specified boundary
Read the sides of a box and a fence boundary, allowing an inside and an outside position to coexist when their reference objects differ.
The inner side of an object or boundary
内側, read うちがわ, names an inner surface or area. 箱の内側に布を貼りました。 says that cloth was attached to the inner surface of the box.
柵の内側で作業しています。 says that work is taking place inside the fence. Use the boundary marked by 柵 to locate the work.
The outer side of the same reference
外側, read そとがわ, names an outer surface or area. 箱の外側にラベルを貼ってください。 asks someone to attach a label to the outside of the box.
手袋の外側が濡れています。 says that the outside of the glove is wet. The sentence does not establish whether its inside is wet too.
Two different boundaries
敷地の内側ですが、建物の外側です。 places someone inside the grounds but outside the building. Apply the grounds boundary and the building boundary separately.
扉の内側という説明だけでは、部屋のどの位置かまでは決まりません。 says that “inside the door” alone does not identify the precise position in the room.
Is 敷地の内側ですが、建物の外側です。 a contradictory location?
Show the answer and why
No. The grounds and the building are different references, so both relations can hold.