Repair or replace… that’s the question? In the commercial roof industry there are flat roofs and sloped roofs. Sloped roofs are less prone to leaks and standing water. The tried and true method for flat roofs over time has been the “hot mop”, otherwise called “bituminous” or “built up”. The other kid on the block has been the single ply, which is in the forms of TPO, EPDM, and PVC. In the last couple decades single ply material has proven to be a solid and reliable alternative, and in some instances even superior to built up roofs.