Quote:
Originally Posted by harryc
In Chicago also as a rule offices are steel w a concrete elevator core - residential are re-enforce concrete. I had thought it was primarily a cost issue.
The more expensive steel being used when there is a demand for large open spaces - most of ours start out with the entire floor open except the elevator core.
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Both concrete and steel are expensive. Custom and larger wide-flange steel beams and girders are, of course, more expensive.
But IMO, the main reason is that steel structures offer more flexibility and larger spans between columns, which allows office tenants to customize the space to their preference and needs. One of the negatives I mentioned is that the intermediate beam supports between girders tend to eat up ceiling height space, which isn't as much of a concern for office spaces because they often use this "lost" ceiling height to hide HVAC, plumbing, and electrical equipment and connections above drop ceiling tiles.
Concrete is used in residential spaces for a few reasons:
1. It's naturally fireproof, so there's no need to regularly go into residential apartments to inspect fireproofing as you would need to do with steel structures.
2. The HVAC, electrical, and plumbing mains mostly remain fixed. And there's no need to run them along the ceiling or permit much customization beyond minor branches because apartments are smaller spaces that are mostly occupied long-term in the same configuration.
3. As such, concrete buildings typically have larger ceiling-height to floor-to-floor-height ratio compared with steel buildings. Therefore, concrete allows developers to build more floors at a shorter building height vs steel.