Standing Seam Systems
Snap-lock panels click together and work well on most homes at moderate pitch. Mechanically seamed panels get crimped with a seaming tool, cost more and hold up better on low slopes and long runs. Both use concealed clips, and on long panels the clips should float so the steel can expand without buckling.
Snap-lockMechanical seamFloating clips
Exposed-Fastener Panels
R-panel, PBR and classic corrugated are the budget metal options, screwed straight through the panel into wood purlins or steel framing. They are common on shops, barns and some homes. The trade-off is that every screw is a potential leak, and the washers will need attention every 10 to 20 years.
R-panelCorrugatedPBR panel
Re-Screwing and Sealant Repair
Failed screws get pulled and replaced with the next size up so the threads grab solid material. The contractor also reseals panel side laps, replaces dried butyl tape at end laps and swaps out flattened foam closure strips under ridge and eave trim. Over-driven screws get replaced, not tightened more.
Oversized screwsButyl tapeClosure strips
Gauge, Coatings and Finishes
Gauge runs backwards: 24 is heavier than 26, and 29 is the lightest common option. Galvalume, coated with aluminum and zinc, generally outlasts plain galvanized in most climates, though not in direct contact with wet concrete or treated lumber. PVDF finishes such as Kynar 500 hold color far longer than SMP paint and cost more.
24 vs 26 gaugeGalvalumePVDF paint
Metal Over Shingles
Going over one layer of shingles with purlins or a synthetic underlayment can skip tear-off. The contractor should still check the decking for soft spots and confirm the local rules. Purlins also create an air gap that helps with heat and condensation.
PurlinsSlip sheetOver-roof
Snow Guards and Oil Canning
Snow slides off metal all at once, and guards keep it from dumping on entryways and gutters. Oil canning, the wavy look on flat panel areas, is cosmetic. Striations, a heavier gauge and correct clip spacing reduce it.
Snow guardsOil canningPanel striations