John La Torre Jr.

QI am installing corrugated metal roofing. What is the best way to cut the roofing to fit a valley?

A: John La Torre Jr., a builder in Tuolumne, Calif., replies: A circular saw equipped with a metal-cutting blade will work just fine. Set the blade just deep enough to cut through the low parts of the corrugation and cut slowly. I have also had good results cutting metal roofing using an angle grinder equipped with a metal-cutting blade. Other tools that work well on corrugated metal are sheet-metal nibblers and sheet-metal shears, which do not produce sparks or metal shavings.

In the absence of any of these electric tools, I’ve had good luck cutting metal roofing using two off-set aviation snips (see photo). Aviation snips have compound cutting action to give them greater leverage for cutting through thicker metal, and the off-set blades mean I can keep my hands safely above the metal. These snips come in two colors: green and red. With the green snips, the waste comes off the right side of the blade, and with the red, the waste comes off the left side. I hold green ones in my left hand and red ones in my right hand. Then with the blades positioned about an inch apart, I make my cut with both snips at once and the waste curls up between them, creating the same effect as sheet-metal shears. This works for cutting across a sheet as well as at an angle.