Flashing, Penetrations, and Edge Metal
This domain tests transitions: eave, rake, ridge, hip, valley, sidewall, headwall, curbs, and pipe penetrations. Most roof leaks in metal systems are at these details, so questions focus on sequencing and material compatibility.
Principles
Water must be directed over the panel, not into it. Use two-piece flashings with a reglet at least 1 in. deep and counterflashing. Match materials: copper with copper or stainless; isolate aluminum from copper and from treated wood.
Eave and rake
Eave: drip edge over the underlayment, panel over the drip edge, closure strip at the pan. Rake: gable trim with a 1 in. return, fastened in the rib, not the flat pan.
Valleys
W-valley 16–20 in. wide, open valley 8–12 in. Fasten only along the outer edges so the metal can move.
Penetrations
Pipe boots: EPDM or neoprene boot on a metal pan; seal and fasten the flange and keep the boot off the rib. Curbs: at least 8 in. above the roof surface and 4 in. above the highest water level, with a butyl-taped flange.
Worked example
A 4 in. vent through a 6:12 standing seam roof. Set an offset boot on a flat pan with a 1½ in. flange, butyl tape under the flange, and stainless fasteners in the pan. Never fasten through the seam, because the seam must be free to move.
Traps
Fastening flashing through the panel face where movement occurs; relying on sealant with no mechanical lap; and setting a 2 in. curb on a low-slope roof.