I live on the 5th floor of a walkup, with the rooftop directly on top of us. The rooftop is actually of the building I'm staying in, and the adjacent building, but nobody ever goes up there. So that leaves around 2000q ft of open space for my dog to run around.
As with HK law, the doorway to the roof is just open, you cannot lock it. In theory, anybody can go up there, but nobody ever does.
With the approval of my neighbours, and keeping my rowdy friends turned down a bit, I've had BBQs up there, and one time even had a hotpot for several hours up there (just threw an extension cable down to my kitchen window, and there's a set of table and chairs up there already).
It's great to hang your clothes up to dry as well. There have been times I just grabbed a cold drink and sat up on the roof, soaking up the sun, its just within my wifi range so I take my phone or laptop with me sometimes.
The downsides are:
- The flat gets hot quite quickly from the heat soaked up during the day from the sun baking it down
- HK air has a huge amount of dust, so you'll see everything up on the roof get covered in it, if you don't clean it off, during the rains (like it is right now) the dust will turn into mud and clog up the drains
- With the rooftop being public access, you don't want to keep anything not chained up up there