You can't stay up here any longer you decide after a day and a half. There's maybe a few less zombies milling about on the streets below. but your average undead head count is eighty seven. You have eaten everything the roof had to offer and you are really thirsty. Its the thirst that drives you back down stairs to the floor levels. It takes you almost a hour to slowly silently take down your barricade and open the metal doors. No sign of the dead in the hall.