Which statement about edge versus field performance is supported?

• A. Edge performance matters due to flow and pressure effects.
• B. Field performance is always controlling.
• C. Edge performance is unrelated to drainage.
• D. Edges never fail.

Answer: (A)

Edge performance matters because the boundary of a roof behaves differently from the interior, with flow, pressure, and drainage patterns that are unique to edges and terminations. Wind flowing over a roof creates complex pressure distributions that are not the same in the middle of the field—edges and corners experience higher suction and vortices, and water is guided toward edges where flashing, joints, and edge details must reliably seal and drain. If edge details don’t handle these boundary effects, leakage and uplift can occur even when the field area seems fine.

This is why the statement about edge performance being influenced by flow and pressure effects is the best choice. It captures how boundary conditions drive performance, making edges critical for overall roof behavior. The other options don’t fit because field performance is not universally controlling, edge performance is indeed related to drainage, and edges can and do fail, especially where flashing or drainage paths are stressed.