Both metals make roofs that outlast asphalt. On the coast from Wilmington and Jacksonville to New Bern, Morehead City and Beaufort, the difference is what each does in salt air.
| Factor | Aluminum (Interlock) | Steel |
|---|---|---|
| Corrosion in salt air | Does not rust; an oxide film slows further oxidation | Protected by its zinc or aluminum-zinc coating; can rust at cut edges, scratches and fastener holes |
| Weight | About one-third the density of steel | Heavier |
| Dents | Can dent cosmetically under large hail | Resists dents better at the same thickness |
| Wind | Interlock panels lock on four sides; wind warranted to 120 mph when installed to manufacturer specification | Depends on the system and fastening |
| Up-front cost | Higher | Usually lower |
Why does salt air matter so much for a metal roof?
Salt air matters because it speeds up corrosion wherever bare steel is exposed. A steel roof lasts as long as its metallic coating and paint keep water and salt off the steel. Aluminum has no steel to reach, so a scratch or a cut edge has nothing to rust. It is corrosion-resistant, not corrosion-proof: flashings and fasteners must be compatible metals.
How do coastal storms factor in?
Coastal North Carolina takes the first hit from tropical systems. Florence came ashore near Wrightsville Beach in September 2018 (NWS Wilmington), and Matthew in 2016 brought coastal gusts above 70 mph (NWS Raleigh). Parts of the coast sit in design wind zones of 130 mph and above under the NC Residential Code, and the permit office or engineer sets the requirement for a given house. No roof is immune to hurricane damage; see hurricane-resistant roofing.
Is aluminum worth the higher cost?
Metal Roof NC's rule of thumb is that an Interlock aluminum roof typically costs about 2.5 to 3 times a traditional asphalt-shingle roof. Prices vary job to job with roof size, pitch, tear-off and other conditions, and an on-site estimate is required for an accurate price. Steel usually comes in below aluminum. On a coastal house you plan to keep, avoiding a coating-dependent roof is the reason to pay more. See metal roof cost and steel vs aluminum roofing.
Where does Metal Roof NC install?
Across the Triangle, the Charlotte area, the Triad and Piedmont, and the coast: Raleigh, Durham, Charlotte, Greensboro, Wilmington, New Bern, Morehead City and more. See all service areas.