Kendall,
Don't forget this:
From the 2006 IRC. (underlining is mine)
- SECTION M1305
- - APPLIANCE ACCESS
- - - M1305.1 Appliance access for inspection service, repair and replacement.
Appliances shall be accessible for inspection, service, repair and replacement without removing permanent construction, other appliances, or any other piping or ducts not connected to the appliance being inspected, serviced, repaired or replaced. A level working space at least 30 inches deep and 30 inches wide (762 mm by 762 mm) shall be provided in front of the control side to service an appliance. Installation of room heaters shall be permitted with at least an 18-inch (457 mm) working space. A platform shall not be required for room heaters.
In a recent ICC publication, they addressed this very issue and included a drawing showing that level working space on the roof (a platform), and, because that level working space (platform) is more than 30" above ground or floor below, they included the required guardrail around that platform to help keep the worker from falling off.
You end up with a pretty massive structure up there, and one would also need to have a structural engineer verify that the roof framing can support *not only the unit* (as in your photo), but also the working platform with guard railing.
This is from the IMC and is a good description of it even for flat roofs:
[b]
- 304.10 Guards. Guards shall be provided where appliances, equipment, fans or other components that require service and roof hatch openings are located within 10 feet (3048 mm) of a roof edge or open side of a walking surface and such edge or open side is located more than 30 inches (762 mm) above the floor, roof or grade below. The guard shall extend not less than 30 inches (762 mm) beyond each end of such appliances, equipment, fans, components and roof hatch openings and the top of the guard shall be located not less than 42 inches (1067 mm) above the elevated surface adjacent to the guard. The guard shall be constructed so as to prevent the passage of a 21-inch-diameter (533 mm) sphere and shall comply with the loading requirements for guards specified in the International Building Code.