The Big O, a new EPDM roofing membrane
Here is a relatively new roofing product, especially when used for residential buildings. It will replace the older tar and gravel roofing systems for flat roofs.
EPDM ethylene propylene diene Monomer (M-class) rubber http://en.wikipedia.org/wiki/EPDM_rubber
In commercial applications large sheets of the EPDM, a rubber type material are laid over the roof surface. If more is needed, other sheet are laid adjacent to the first and overlap. The overlapping seams are glue/welded together to create a watertight membrane that covers the whole roof and extends up the sides of parapet walls to under the cap flashing. All passthroughs and openings are sealed in the same manner.
In some applications the membrane is weighted down rater than being mechanically attached. This allows for large widths to expand and contract with out detriment or leaks at attachment points.
Residential applications can be done differently as they usually are not as large. At regular intervals large disk like washers are screwed to the sheathing/framing below (often through new layers of rigid insulation). The disks are then covered with glued down patches of the same roofing material.
Original blog post on ActiveRain: Link to Blog Post