How to Install Corrugated Polycarbonate Sheet Patio Covers

Measure the patio space. Install the support posts every 8 feet around the perimeter. Determine the angle of the rafters and install them according to the local building codes. Generally, the recommended pitch, or rise, of the rafters is 1 1/2 inches per foot.

Add purlins every 2 feet across the tops of the rafters. In a lightweight application such as a patio roof, a purlin is usually a 2-by-2-inch board that spans the rafters.

Measure and cut 2-by-2-inch boards to block the ends of the outside rafters, providing additional vertical support to the polycarbonate panels. Attach them to the rafters by running a bead of construction glue onto the support; then predrill and screw them together with 3-inch deck screws.

Attach the corrugated closure strips to the tops of the purlins. Glue and screw them together with the screws recommended by the manufacturer.

Align the first corrugated panel on top of the purlin, beginning at the outside edge of the patio cover. Predrill and screw the panel to the purlin at the top of every other corrugation.

Measure and cut a piece of panel to fit between the first panel and the inside edge of the patio if necessary. Overlap the panels by at least 6 inches. Run a bead of silicone sealant along the top of the first panel. This will prevent leaks. Predrill and screw the panels to the purlins.

Use the remainder of the second panel to start the second row. Run a bead of silicone sealant along the long edge of the first two panels. Place the third panel at the outside edge of the cover, overlapping the first panel by one full corrugation. Predrill the panels and screw them to the purlins.

Measure the space from the third panel to the inside edge of the patio cover. Add 6 inches to the measure, then cut the fourth panel to fit. Apply silicone sealant, predrill the panel and screw it to the purlins. Continue installing panels until the patio is covered.

Lay a long board across the polycarbonate panels. Use the board to distribute your weight as you install flashing between the top of the panels and the wall of the house.