Aluminium vs Steel: Which Suits Your Structure Best?

A client recently asked me whether aluminium framing would offer an advantage over steel. My answer: an advantage in what?

That conversation inspired this eight-round engineering showdown.

Aluminium weighs roughly one-third as much as steel for the same volume. Steel has roughly three times the elastic modulus—but that does not mean three times the strength.

Steel retains strength better at elevated temperatures. Aluminium offers lightweight handling and complex extruded profiles, but its weld zones and wet connections to dissimilar metals need careful detailing.

And a lower price per kilogram does not necessarily mean a cheaper finished structure.

These two images put the advantages and weaknesses side by side—from stiffness and strength to corrosion, fabrication and cost.

My approach is simple: define what the structure needs, then choose the material.

Which would you put in your corner?