Aluminum roofing and siding sheets are rollformed from hardened, tempered metal for maximum strength. If a sheet must be bent, a gentle 90-degree bend is the maximum recommended. Metal should not be re-bent once it has been formed, nor should it be folded back on itself, since it is not designed to take a lockseam. When a metal roofing sheet must be installed on a curved roof, screws should be installed at every overlapping rib at the sheet ends to resist the natural tendency of the metal to spring back. Standard fastener spacing is permitted over the rest of the sheet. When installing the metal roofing and siding panels shown in this booklet over a curved arch, the minimum radius of the arch is 18' for aluminum profiles and 24' for steel profiles. Use sealant tape or butyl caulking at all sidelaps and endlaps.
Additional care and fasteners must be provided when securing the top and bottom purlins on a laminated rafter building to prevent the curved panels from pulling the purlins loose from the rafters. Ringshank pole barn nails, heavy wood screws, lag screws, or bolts are often used for attaching these purlins.
If siding sheets are installed horizontally, use sealant tape or butyl caulking at the vertical laps to ensure weathertight joints. Install panels from the bottom up so that water is directed away from, and not into, the lap joints.
The FabrOseal® galvanized ring-shank nail, with its premium long-life silicone rubber gasket, assures a lasting seal and is the best nail available for steel panels when screws are not desired.
The correct way to fasten steel panels with nails is to drive the nail through the top of the rib so the washer is compressed securely against the metal. Nail placement must be in the ribs for roofing applications to minimize the potential for roof leaks. Over-driving the nail can split the washer and dimple the metal, causing leaks.
Wood screws with combination metal and neoprene washers should be installed in the flat area of the panel adjacent to the ribs, and tightened such that the washer is compressed as illustrated above. This will ensure a lasting, leak-proof seal. See pages 4 to 5 for the correct fastener locations.