The test frame has the appropriate roof deck attached to supports. Insulation (any type) is then fastened to the deck and the single-ply membrane is secured over the insulation to the deck. The test frame is clamped to a pressure vessel that is pressurized to 30 psf and held at that level for one minute. Assuming that the roofing system remains undamaged at the end of the first minute, the pressure is increased to 45 psf and held for another one-minute period. This process is repeated in 15 psf increments until any component of the system fails. The approval for that assembly is established at the level preceding failure. The minimum wind approval rating is 60 psf. For example, if the pressure level was at 105 psf when the failure occurred, the Approval level would be set at the preceding level or 90 psf, giving the assembly a 1-90 rating.