Standard metal roofing panels attach to rafters and purlins with a set of specialised sheet metal screws. Unlike standard sheet metal screws, metal roofing panel screws have a broad head encircled with a rubber washer and a drill-like, self-tapping screw tip. The screws' washers sit snugly against a roofing panel's surface to create a waterproof seal. Additionally, the screws' self-tapping tips reduce installation time by eliminating the need to pre-drill screw holes.
Place a roofing panel at one the roof's bottom corners. Hang 2 to 3 inches of the panel over the roof's eave and 2 to 3 inches over the roof's gable end; in other words, hang the side of the panel over the rafter at the end of the roof.
Slide the panel up or down to align its top and bottom edges with purlins. Purlins are the roof framing members that run horizontally across the roof's surface; for metal roofing panels, purlins are typically capped with a foam or wood support strip in the shape of the panel's profile. Use purlins as a guide to horizontally level the panel's top edge, and joists or rafters as a guide to vertically level the panel's side edge.
Select a nut driver that fits snugly around the roofing screw's hexagonal head. Similar to socket wrenches, nut drivers are screwdriver bits in the shape of a hexagonal cylinder. Attach the nut driver to a power drill. Mount a roofing screw into the nut driver's opening.
Press the screw's self-tapping tip against the roofing panel near one of the panel's upper corners and in the valley or flat section beside one of the panel's ribs. While maintaining forward pressure, slowly activate the drill and allow the screw's self-tapping tip to bore through the metal roofing panel's surface. Drive the screw through the panel and into the underlying framing.
Drive the fastener until the screw's rubber washer snugly seats against the metal roofing panel's rib. Avoid excessive tightening; driving the screw too far creates a depression in the metal, which allows water to pool around the screw and possibly leads to leaks.
Drive additional screws along the edges of the metal roofing panel and along purlins that cross the panel's centre. Space screws according to the metal roofing panel manufacturer's instructions, typically every 6 to 8 inches. Do not fasten screws along the rib on the edge of the panel that faces the centre of the roof; the next panel must overlap this rib.
Position a second panel on the roof next to the first and overlap the panel's edge rib with the first panel's edge rib. Align the second panel with the horizontal level of the first panel. Fasten screws through both sides of the overlapping rib. Apply fasteners to the remaining edges and centre of the panel. As with the first panel, do not fasten screws to the rib on the edge of the panel that faces the centre of the roof.
Install subsequent panels the same way. When you reach the end of the roof, move toward the roof's peak to install a second course of panels. Overlap the second course over the first one by 2 to 3 inches.
Self-tapping, rubber washer roofing screws also work with corrugated vinyl roofing panels. For large projects, consider specialised tools; many home improvement stores rent screw guns that automatically drive and reload roofing screws.
Tips and warnings
- Self-tapping, rubber washer roofing screws also work with corrugated vinyl roofing panels.
- For large projects, consider specialised tools; many home improvement stores rent screw guns that automatically drive and reload roofing screws.