Panel installation should begin at the gable end of the roof opposite the prevailing rain-bearing wind (this will provide added protection against wind-driven rain being forced under the laps). Measure one panel width in from the roof edge. At this point, chalk a line from ridge to eave. Place the leading edge of the first panel along this line. It is extremely important that this panel be laid square to the eave and ridge so that the remaining panels will line up square on the roof frame. It is recommended to have a person at the eave and at the ridge to ensure that the proper panel coverage is being maintained across the roof. Also be sure that the panels are properly side-lapped.
In applications where end-lapping is necessary, the upper panel on the slope should lap over the panel that is lower on the slope by about 12 inches. Lesser roof pitches require a greater amount of panel overlap. All end-lap applications should use 2 horizontal rows of butyl sealant tape across the panel and proper fastening to provide a maximum water seal.
An overhang of 2 to 3 inches on the eave is recommended to provide a drip edge, while only 1 inch overhang is necessary where gutters are used. The open panel ribs at the eave can be sealed with inside closures. For maximum weather-tightness, a row of butyl tape can be applied above and beneath the closure material.