Visited NYC this past weekend and saw multiple buildings that were at least 30-40 stories high, but the base wasn’t finished yet. Why do you keep building upwards and finishing windows instead of finishing the bottom and then doing the same?
In: Engineering
> Why do you keep building upwards and finishing windows instead of finishing the bottom and then doing the same?
Many large buildings are designed with the assumption that their outer shell will be in place, not that their frame will be exposed to the weather. Beyond the aesthetics there is also a safety angle to consider, where ongoing work within the building can benefit from a barrier between them and open air. You probably don’t want to start laying down carpet when there aren’t even windows in yet.
Try thinking about your question in the context of a smaller building, like a 2 story house. How do you think you are going to feel living on a fully furnished first floor, when the second floor is unfinished and there is no roof? What do you think is going to happen when it rains?
Imagine walking in to the completed first floor of your skyscraper and wanting to go up to the 4th floor to your office. The receptionist is like “Well, you can’t take the elevator because the cables anchor at the top and that isn’t like… built yet. Also the elevator shaft is open to the sky for the top, like, 20 floors, so it is basically a waterfall sometimes. The same for the stairwells really. There was some engineer here saying something about most skyscrapers needing a mechanical floor about every 10 floors, so that might be why the toilets, air conditioning, and electricity doesn’t work. But yah, there is like, furniture there, or whatever.”
As far as the primary construction crew is concerned the base *is* finished: It is structurally complete and able to support the upper floors. At that point you move on to building the upper floors so you can fill (lease, sell) them.
Leaving the lower floors unfinished lets you hoist material through them and use the lower floors as staging areas for further construction without having to worry about damaging a finished area of the building, so the interior is usually finished out top-to-bottom.
The ground floor is the ***last*** thing you *can* finish: It’s going to be decorative lobby space (you don’t want construction crews tracking through your multimillion dollar lobby), or commercial retail space (you won’t finish that at all, you’ll rent it to a tenant and they’ll build it out the way they want it), or some combination of the two.
As far as the windows go these are usually non-structural curtain walls, but you need to put them in and enclose the basic envelope of the building before you start installing anything on the floors that might not take too kindly to the weather (plumbing, drywall, flooring, etc.) and before you can do basic climate control (at least minimum heating in winter so when you fill fire standpipes and other water lines they don’t freeze & burst).
Perhaps a large part of what you are describing as “not finished” is a pedestrian protective scaffolding used to prevent pieces of facade from killing anyone when it falls off the buildings. A lot of buildings’ facades need to be brought up to code (read: expensive) and until they they get fined (I think) but definitely have to construct those pathway things so people don’t get hurt (read: less expensive)
The bottom floors are often retail spaces separate from whatever the rest of the tower is used for. The business renting that retail space will do their own construction after the primary tower is finished.
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It also allows you to finish the floors that get closed, as in put in walls and fixtures like cabinets and finished bathrooms and kitchens.
You would t do that while exposed to the weather.
Doing it this way saves money on the construction project and allows the finished building to be opened faster.
You’ll even have floors on top that don’t have windows yet while the lower floors are already being finished.
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