Construction and engineering costs skyrocket after like 1000' or something. Obviously there are a lot of factors at play but what makes you say it'd be "about the same"?

^ That's what I've heard as well, and is the reason why so many 700-to-900 footers are being proposed and constructed: apparently that's the sweet spot in terms of benefit-cost ratio. For skyscraper fans this can be disappointing, since some of the 900+ footers would be supertalls if they were just a tad taller, but most developers don't care about that, as mentioned earlier in this thread.

I suppose some of know more about construction costs than myself. Question: What would the cost be of the time digging, drilling, foundation creation, ect., and then getting to grade and then the first 8-10 floors for a 50-60 story office building?
I've heard some of these arguments for years....Just currious I guess.

Why not a 5,000' office tower where the loss factor is 54%?

Very interesting, but does the cost become prohibitive over 1000 feet if you add a crown or something of that type. You may be right though about benefit-cost ratio, maybe that is the reason some newly built or proposed New York skyscrapers are in the 50 to 60 story range but with crowns or antennas list over 1000 feet. Even so if 301 and 325 Wacker Drive twin towers had sizeable crowns atop them both, that would be awesome...

From my 3D model of Chicago.

https://images2.imgbox.com/88/b3/bFSBBOjl_o.jpg

https://images2.imgbox.com/17/7c/GFFnZ0Wm_o.jpg

https://images2.imgbox.com/a1/15/ZG9QZkG2_o.jpg



Bonus shots of the unbuilt original proposal.


https://images2.imgbox.com/57/b1/AQtkmagM_o.jpg

https://images2.imgbox.com/45/e6/9LvRukMs_o.jpg

https://images2.imgbox.com/07/d9/hnuora3a_o.jpg

For you and me it might seem like a no-brainer to spend another, say, $500k to add some vanity height, but most penny-pinching developers would disagree.

Luckily a few developers do care for vanity height and bragging rights. Look at Chicago's 6th and 7th tallest buildings, Franklin Center and 2 Prudential Plaza. Their roofs are only around 900 ft, probably to keep the benefit-cost ratio reasonable, but both have spires that go just high enough to reach supertall status.

At only 775', 301 & 321 S Wacker Drive are too far below the 984' mark to ever become supertalls -- they would look rather silly with 210' spires -- although it's still nice that they will be the tallest identical twin buildings in North America, assuming their heights aren't cut. NOTE: The "twins" at Harbour Plaza in Toronto are not identical.

Being right next to Sears/Willis, these "tallest identical twin buildings in North America" look like midgets. *SIGH*

Nice work rgarri, although I must say 311 South Wacker triplets looks a bit odd.

Not sure reaching supertall status was intentional for those buildings, I don't think most developers care about such an arbitrary number or even know it exists.

Spires are kinda lame unless they really fit the design, I'd rather just have two 775' buildings with cool roof gardens.

Well yea, Sears is huge

New proposal looks way better than 3 of 311 S Wackers. That just looks weird. Good work as always rgarri

I agree with all parts of this

yeah how much office space does white castle really need

^^lol! Lots of "Sliders"!

That's not at all what the original plan was. Pure artist embellishment. But thanks for playing.

At any rate, I'd like to see something significant go up on that site before I croak!

Ugh if only they had built the other two, would have been a perfect postmodern paradise

^ blech

One 311 s wacker is too much as it is.

Perhaps my least favorite major tower in the skyline.

Go back a page. I doubt the developer would use a non serious artist embellishment to advertise what they were planning.

311 S Wacker
 

Three 311 S Wacker's look too much like a housing project. Thanks for the modeling but one is plenty.

FWIW, I remember seeing the plan for additional two towers back then. They were diagonally connected to the two "wings" (if you will) on the existing 311 S Wacker. Not free standing. Look at the existing building design. Those offshoots on the back/sides of the building were designed with that in mind. I can't say when the massing design on the previous page came exactly. Maybe it was much earlier in the process. As you can see in that design the towers were hexagonal, for example. The final is octagonal.

According to This a zoning variance has been granted for these to reduce the parking requirements provided that construction starts by July of 2022.