What dictates whether a building will be built in steel or concrete

[IluvATX]

I’m wondering what dictates whether a building will be built with steel or concrete. It seems to me NYC and east coast is all steel, while the the west is all concrete. Is it codes, availability of building materials, or what?

[mhays]

Many things...for offices, it's often not decided until fairly late in design in my region.

As a non-technical general contractor guy, here's my take:

Price. The two rise and fall relative to each other. Tarrifs have wreaked some havoc on this one. (Each has components of the other, such as the slab on metal deck with steel buildings, and the rebar in concrete.)

Seismic. In seismic zones, structures want to be a mix of rigid and bendable. A steel building will typically have a concrete core.

Speed. Steel requires long lead times, but it goes up quickly. But with the much slower concrete core, some of the advantage disappears.

Spans. Steel tends to make sense for longer spans, and the longer the span or more loads on it, the more stark this is.

Ceiling-to-floor depth. Some concrete designs are extremely skinny. This can include skinny slabs (particularly with post-tensionioning) and the choice to omit beams by putting in more columns. Post tensioning involves cables at high tension that bow the concrete upward, allowing less concrete to be used.

Acoustics. A concrete building will tend to be much quieter than steel even with a thin concrete slab on the metal deck in a steel building. That's one reason housing likes concrete. (Housing also does well with those skinny floor-to-floor heights and frequent columns.)

Vibration. Laboratories are often vibration-sensitive (microscopes etc.), and prefer concrete. Alternatively you can focus certain lab functions closer to the concrete core and add more steel for this.

Penetrations. Tenants often want to drill through the floors for mechanical/electrical systems. In a concrete building with post-tensioning, this needs to be carefully managed to avoid snapping a cable and killing someone.

Weight. A steel building tends to be lighter.

Detailing. Structural choices affect other elements quite a bit, such as the 1,000,000 details involved with curtain wall. I don't know which tends to be easier but it's a factor.

And so on...

[Steely Dan]

speaking in terms of the chicago market for highrise/skyscraper construction, the determining factor for steel vs. concrete is mainly the intended use.

95% of the time, residential towers are reinforced concrete structures. conversely, 95% of the time, office towers are reinforced concrete cores with steel framed structural bays.

office plans desire the flexibility of open, column-free wide-span spaces, which structural steel excels at.

residential/hotel plans can MUCH more easily accommodate the typically tighter column grid of a concrete structure.

[sbarn]

Originally Posted by IluvATX

I’m wondering what dictates whether a building will be built with steel or concrete. It seems to me NYC and east coast is all steel, while the the west is all concrete. Is it codes, availability of building materials, or what?

That is actually untrue. NYC is typically concrete except for major office towers. The Central Park Tower, Steinway Tower and 432 Park are all concrete construction.

Boston on the other hand is usually steel.

It really has to do with the building design, seismic considerations, local market subcontractors, unions and cost.