Maritimes · Steel vs aluminum
Steel vs aluminum roofing near salt water
A steel roof is protected from rust by its zinc or aluminum-zinc coating and paint, and lasts as long as they do; salt air is one of the harder environments for that coating. An aluminum roof has no steel to rust: its oxide film protects it, and it weighs about a third as much. Steel usually costs less up front and dents less; aluminum is the longer-lived choice near the coast.
Reviewed by Scott Plumptree, Director of Marketing, The Interlock Group · Updated October 8, 2026
Steel
Protected by its coating
Galvanized (zinc) or Galvalume (aluminum-zinc).
Aluminum
Protected by the metal itself
An oxide film blocks further oxidation.
Weight
Aluminum ≈ one-third of steel
By density, ASM International.
Side by side
| Steel roofing | Aluminum roofing | |
|---|---|---|
| What keeps it from corroding | A metallic coating, zinc (galvanized) or aluminum-zinc (Galvalume), under the paint | The aluminum itself: its oxide film blocks further oxidation |
| Near salt water | The coating does the work, and coastal air is one of the harder environments for it; the coating maker asks to be consulted for unusually corrosive environments | Contains no iron, so there is nothing to rust |
| If the finish is scratched or cut | The steel is protected only as long as the coating around it lasts; galvanized cut edges are bare steel once the zinc nearby is used up | Bare aluminum forms the same oxide film; there is no steel to rust |
| Weight | Heavier | About one-third the density of steel |
| Dents | Thicker steel resists denting better than thin aluminum | Can dent under foot traffic, falling branches or large hail; dents are cosmetic and usually excluded from warranties |
| Up-front price | Usually lower | Usually higher |
| Things to avoid | Galvalume corrodes quickly in contact with wet mortar or concrete | Keep it out of direct contact with dissimilar metals; flashings are matched to the system |
| Typical buyer | Lowest up-front cost | Longest-lived option; a house you plan to keep, especially near the coast |
Steel: ArcelorMittal Dofasco (Galvalume product information) and Gibraltar Building Products. Aluminum: ASM International. References at the end of the page.
Aluminum roofs on the Maritimes coast
Recent Interlock® roofs installed in the Maritimes by our own company. Tap a roof to see all of its photos.
Salt air is the Maritimes question
Most of the Maritimes is close to salt water, and fog covers Nova Scotia's coasts 15 to 25 per cent of the year, according to the Nova Scotia Museum. ArcelorMittal Dofasco, which makes Galvalume steel, describes coastal regions as among the more corrosive environments in North America, and asks buyers to consult it before using Galvalume in unusually corrosive environments.
A steel roof near the ocean can still be a good roof: its life depends on how well its coating and paint hold up, which is why steel warranties are written in years. An aluminum roof takes the coating question off the table. An Interlock® panel has no steel in it, so a scratch, a dent, a cut edge or a fastener hole has nothing to rust.
Why many metal roofers sell steel
Steel coil is widely available and costs less, which is why many metal roofers sell steel: painted steel panels, steel shingles and stone-coated steel. A good steel roof, well installed, is a sound roof, and on a barn or a shed it is often the sensible choice.
We install aluminum because the homes we roof are mostly ones people keep: older wood-frame houses, century homes, cottages on the shore. For those, a roof that can't rust is worth the higher price up front.
Questions that settle it for your house
- How long do you plan to own the home? The longer you stay, the more a roof you never replace is worth.
- How close are you to salt water, and how exposed is the lot to wind and spray?
- Do you want a slate, cedar or tile look, or plain panels? Profiles differ more than metals.
- Who is the warrantor, the manufacturer or the contractor, and what does the material warranty cover after year ten?
- Are the fasteners concealed or screwed through the face?
Questions, answered
Is steel or aluminum better for a roof near the ocean?
Both make good roofs, but near salt water aluminum has the edge: it contains no iron and can't rust, while steel depends on its zinc or aluminum-zinc coating, which salt air works on. Steel costs less up front. For a house you'll keep, aluminum is the longer-lived choice.
Does a steel roof rust?
Steel itself rusts; a steel roof is protected by its metallic coating and paint. Where the coating is cut, scratched, cracked by a dent or used up, as at galvanized cut edges over time, rust can start.
Does an aluminum roof rust?
No. Aluminum forms an oxide film that blocks further oxidation, and there is no steel in an aluminum roof to rust, even in salt air.
Which dents more easily, steel or aluminum?
Thicker steel dents less; aluminum dents more easily but has no steel to rust where it dents. Dents on either are usually treated as cosmetic by warranties.
Is aluminum roofing more expensive than steel?
Usually, yes, up front. Our metal roof cost page shows real ranges from our recent Maritimes contracts, and we give a fixed price in writing after one free visit, so you can compare it with a steel quote line by line.
Who installs aluminum roofing instead of steel in the Maritimes?
Maritime Metal Roofing Ltd., founded in 2007, installs the Interlock® aluminum roofing system across Nova Scotia, New Brunswick and PEI from its office in Dartmouth. Our job book holds 5,581 Maritimes roofs, the first in 1995. Call (506) 799-0209.
Sources
- ArcelorMittal Dofasco: Galvalume™ steel sheet, product information
- Gibraltar Building Products: why are the edges of my painted galvanized roof rusting?
- J.R. Davis, "Aluminum and Aluminum Alloys", Alloying: Understanding the Basics, ASM International (2001)
- Interlock Roofing: Aluminum vs steel roofing
- Nova Scotia Museum: Natural History of Nova Scotia, Vol. I, T5.1 The dynamics of Nova Scotia's climate
- Interlock Roofing: aluminum shingles, technical specifications
- Guardian Lifetime Limited Material Warranty (full terms)
Product specifications are the manufacturer's (Interlock Roofing). Install counts are from our own job book. Reviewed by Scott Plumptree, October 8, 2026.
Compare an aluminum quote with your steel quote.
A fixed price in writing after one visit, at your home or on Zoom. Maritime Metal Roofing Ltd. · 101 Thornhill Dr #105, Dartmouth, NS B3B 1S2
