What to expect during flat roof installation: Property protection and coverage using plywood and tarps. Removal of ALL old roofing material. Repair and replacement of rotten boards/plywood decking underneath the flat roof if needed. Re-nailing and re-securing of roof deck.  This will help enhance the look of the roof by providing a flat surface to install the new material to and minimize the chance of premature cracking to roofing material. Inspect roof decking for adequate slope for drainage