What is the basic info on metal roofs: types, metals and finishes?
Short answer. Residential metal roofs come in four main styles: standing seam, exposed fastener panels, stone-coated steel and metal shingles. Most are steel with a zinc or aluminum-zinc coating, sold in gauges such as 29, 26 and 24, where a lower number means thicker metal, and finished with paint systems ranging from basic polyester blends to long-life PVDF.
The four styles
- Standing seam: long vertical panels joined by raised seams, held with hidden clips that let the metal expand and contract. The premium residential option.
- Exposed fastener: corrugated, R-panel or 5V panels screwed through the face with sealing washers. Lower cost, common on barns, porches and some homes, with screws that need periodic attention.
- Stone-coated steel: steel panels coated with granules and shaped like shingles, shakes or tile. The textured surface hides small dents.
- Metal shingles: pressed steel or aluminum pieces that interlock, made to look like slate, shake or shingles.
Metals
- Galvalume steel: steel coated with an aluminum and zinc alloy. The most common residential choice.
- Galvanized steel: zinc coated, common on agricultural panels.
- Aluminum: will not rust, which makes it the usual choice near salt water, but it dents more easily.
- Copper and zinc: premium metals, mostly for accents, bay windows and historic homes.
Gauge and finish
Gauge is thickness: 29 gauge is thin and economical, 26 is a common middle ground, and 24 is typical for quality standing seam. Finish matters as much as metal. PVDF coatings, often sold under the Kynar name, resist fading and chalking far longer than SMP coatings, and the paint warranty is usually separate from the metal warranty.
Installation basics
Homes usually get metal over solid decking with a high temperature underlayment. Purlin systems with an air gap are more common on outbuildings and over existing shingles.
See metal roofing in Georgia and synthetic underlayment vs felt.