Why is concrete/rebar construction cheaper than steel frame construction?

[hawc]

It seems these days everything is built with rebar and poured concrete. All our buildings, all our bridges, everything. Years ago this would have been steel frame construction using girders and steel sheet flooring.

Why is concrete/rebar cheaper? Seems like there's a lot of framing work to be done before each pour and lots of complicated rebar bending and placing. Are the materials dramatically cheaper?

I'm baffled.

 

[Nads Gone Bads]

I wish we used to steel frame so we could get buildings completed at a faster clip. Trump has been under construction for over 4 years and still has months until it's completed.

 

[Admiral Beez]

I'm the marketing manager for a major Canadian/USA/global construction productions firm. I asked our engineers this question this morning. Answer is that steel frame construction needs either labour-time intensive manually installed riveting or expensive and and complicated welding. Lastly, the cost of refined and specialized steel for framing is skyrocketing.

On the other hand concrete is cheap and plentiful - after all it's just a mix of limestone gravel, sand, water and a few chemical additives. Rebar is the cheapest form of rolled steel, generally produced in low tech mini-mills.

Lastly, it comes down to logistics. When building in concrete/rebar the builder can install a portable concrete plant right on site. Plus in many cases mini mills for rebar can also be re-located close to the building site. Imagine instead the cost of shipping and forward planning for all the framed steel from the huge steel mills in Hamilton or in the USA.

 

[hawc]

Interesting! Thanks for the answer!

 

[pman]

It's interesting though. The US seems to mostly opt for steel instead of concrete, and I would guess the same economics apply there as well.

 

[TrickyRicky]

Also, seismic, fire rating, sound, and other performance measures influence the decision-making from the technical perspective. Local standard practices and precedents also do influence the outcome, as do local supply issues and even things as obscure as what industry the mob historically controlled.

Logistically in Toronto we have historically had cheap and technically acceptable aggregate for concrete as well as cheap and abundant power supplies for manufacturing concrete. The manufacturing of concrete uses a lot of energy and generates something in the order of 20 percent of all man-made greenhouse gases. Many areas have minerals in the local rock used for agreggate that de-stablize the concrete over time. In addition, seismic requirements and proximity to say ocean salts are not as much of a consideration and the construction of large buildings is a more recent phenomenon vis a vis many large centres in the US.

 

[wopchop]

Another limiting factor is labour. Unionized ironworkers connecting steel make significantly more than unionized formworkers. Sure, you have ironworkers tying rebar, but you've still drastically cut down your expensive labour force.