Which of the following is considered a non-standard structure?

A non-standard structure in the context of telecommunications towers typically refers to configurations that do not conform to the common design types used in the industry. Rooftop structures fall into this category because they are not built as standalone towers like free-standing towers, monopoles, or self-supporting structures. Instead, rooftop installations use existing buildings or structures as their base, making them more complex in terms of permitting, safety considerations, and structural integrity.

Rooftop installations may involve several unique design challenges, including the need to ensure that the building can support the additional equipment and antennas, as well as compliance with local zoning laws. This contrasts with traditional tower forms, which are specifically designed for telecommunications purposes and follow well-established engineering standards.