You may be looking for the webcomic by this name.
Generic Surface is what buildings tend to be made of in badfics until they are properly described. It has also been harnessed by the PPC for the construction of the vast majority of Headquarters.
Its properties are somewhat undefined, but in HQ it is grey (unless painted), and while structurally sound, and apparently non-compressible, can be broken by sufficient applied force. This makes Building Maintenance Agents very unhappy, especially when there is a All-HQ Australian Indoor-Rules Quiddich League match being played.