According to Ariela Pelaia, professional Jewish Educator and ‘Judaism Guide’ on About.com:
‘A sukkah usually has at least two and a half sides, which can be constructed of any material so long as the sides are secure and don’t flap in the wind. The roof must be made of natural, unprocessed materials that have grown in the ground - such as tree branches, bamboo poles or even wood that’s been shaped into planks. In addition, the roof should be left open so that people inside the sukkah can see the sky.’
This also describes at least half of the apartments I’ve rented in Los Angeles.
At least they were rent controlled…..