Most Industrial buildings usually have some sort of mechanical fixtures on the roof to exhaust fumes or air condition the building etc. Most commonly found are air conditioning units, exhaust fans and HVAC units. Installing these fixtures properly and securely is critical to having a sound roofing system. Most problems occur at curbs and corners of protrusions and walls.
Most houses that have flat roofs usually do not have mechanical equipment on them. However sometimes you will find smaller Split Units that supply cold air for central cooling systems. It is important that these are properly mounted on the roof with some sort of foam support to prevent damage to the roof.