Part of a building - What is it called?

Here is the really quick (like 2 seconds quick) sketch I made up earlier when asking various people here what it was called.



I am aware my scribble scratch is hard to read so I will attempt to explain. We have a building, two stories, the lower portion is a bar. Upstairs, accessed by external stairs along the side of the building leading to the first floor roof, is two apartments. The roof area thing at the top of the stairs is the only access to these apartments. What is the roof area thing called?

It is not a veranda (there is no overhanging roof). Nor is it a balcony (not projecting from the building). Isn't a porch since it is on the roof of the first floor and spans the entire length of the building (and half the width). Patio should be on the ground, this isn't. Best I could think of is a "deck" or "terrace" but it doesn't really feel like either fits. 

Suggestions?