Chicago -Taller thinner residential buildings ?

[chicubs111]

Just curious how come there isnt so many of the taller thinner residential variety of buildings in Chicago? I mean i know of Park tower and Elysian (waldorf) but you dont see many buildings over 500ft that have the multiple setback or wedding cake design style that you see in NYC apt/condos. You typically see many Chicago residential buildings as blocky or solid buildings all the way up?..actually many are seeming to look much alike each other..any reason for this weather its cost related or just an architecture style that is preferred in city? ....Don't get me wrong i know there is some great residential like marina city, legacy , lake point,etc

[mthd]

cost. costs per salable square foot go up very rapidly as height increases past 500 feet or so, and they also go up very rapidly as the size of an average floor decreases. if a floor is 12,000 square feet, it might be 80% usable area, thus adding a 25% "load" of support area for each salable foot. if the floor is 7,500 square feet, it might be only 65% usable area, which means every salable foot has to pay for .5 square feet of support area. the two factors together mean that to build very tall and slender buildings, you need much higher prices per square foot than Chicago commands. the super tall skinny buildings in manhattan are commanding several thousand dollars per square foot - many times what anyone would pay in Chicago.

Some cities also have code issues which make it very difficult. San Francisco has some elevator and stair requirements, which together with the high seismic zone make very small footprint residential towers just about impossible.

[fflint]

Originally Posted by mthd

San Francisco has some elevator and stair requirements, which together with the high seismic zone make very small footprint residential towers just about impossible.

I cannot speak to whether existing building code stair/elevator requirements do or do not make (new) small footprint residential towers impossible, but seismic issues are not obviously a factor. SF's existing tall/thin residential towers have not suffered any notable earthquake damage over the decades. Because developers can make a lot of money with taller buildings, and because the views are great, I suspect there would be a lot more of these if it weren't for modern-day NIMBYism:


http://tobiaspeciva.photoshelter.com...000lAHuhRdL7WU

[ardecila]

Yeah, it's financial. Unless you can sell to the top of the top, the 0.2% of Chicago (as the Lagrange towers attempted) the economics don't work. The size of the core doesn't scale with the size of the floorplate, so skinnier buildings are less efficient.

NY and Vancouver also have an advantage with bedrock close to the surface. In Chicago or Miami*, the loads concentrated by a building greater than 600-700 feet tall require drilling caissons to bedrock, which IIRC is about 200' down. This is really, really expensive, so you can only justify it with large efficient floorplates and a strong dose of ego.

*whoops, miami doesn't have bedrock. the strategy there is to sink tons of relatively shallow piles or caissons and link them with a huge mat or pile caps.

[mthd]

Originally Posted by fflint

I cannot speak to whether existing building code stair/elevator requirements do or do not make (new) small footprint residential towers impossible, but seismic issues are not obviously a factor. SF's existing tall/thin residential towers have not suffered any notable earthquake damage over the decades. Because developers can make a lot of money with taller buildings, and because the views are great, I suspect there would be a lot more of these if it weren't for modern-day NIMBYism:


http://tobiaspeciva.photoshelter.com...000lAHuhRdL7WU

I love that building!

... but seismic costs are not insignificant when it comes to tall slender buildings. current codes require no life threatening damage (this includes stuff falling off the facade) in a 500 year earthquake, which generally require le reducing floor to floor drift to about 1/320 of the floor to floor span. for something with an aspect ratio much beyond 6:1 and especially 10:1, that eats a LOT of floor space in the building.

but those are surmountable problems if the $$$$ on the revenue side are there. unfortunately good architecture and engineering can't overcome short sighted and selfish nimbyism.

[jodelli]

Originally Posted by ardecila

Yeah, it's financial. Unless you can sell to the top of the top, the 0.2% of Chicago (as the Lagrange towers attempted) the economics don't work. The size of the core doesn't scale with the size of the floorplate, so skinnier buildings are less efficient.

NY and Vancouver also have an advantage with bedrock close to the surface. In Chicago or Miami*, the loads concentrated by a building greater than 600-700 feet tall require drilling caissons to bedrock, which IIRC is about 200' down. This is really, really expensive, so you can only justify it with large efficient floorplates and a strong dose of ego.

The foundations of both Trump and the Spire were sunk into dolomite to a depth of c. 120 ft, the last 20' of which were actually below the rock surface. This was done to ensure that load bearing capacity bypassed any weathered rock surface.
It's expensive as you said, especially as the initial excavation has to pass through unconsolidated fill, sand, gravel, and maybe even boulders before hitting saturated clay and then hardpan.

Originally Posted by ardecila

*whoops, miami doesn't have bedrock. the strategy there is to sink tons of relatively shallow piles or caissons and link them with a huge mat or pile caps.[/I]

Same with some of the Gulf Coast cities, where bedrock is just a rumor.

[Crawford]

Originally Posted by ardecila

NY and Vancouver also have an advantage with bedrock close to the surface.

I doubt bedrock plays any role. Maybe 100 years ago it mattered.

At least in Manhattan, there's no present correlation between bedrock variability and relative height.

Some of the tallest, skinniest Manhattan towers are in former swampland or landfill.

[ardecila]

The whole of Manhattan is underlaid by relatively shallow bedrock IIRC even if there is a shallow surface layer of clay or sand.

You're right in some sense, though... Sky-high demand allows NY developers to feasibly construct deep, complex foundations regardless of the depth to bedrock.

[denizen467]

IIRC the shallow bedrock in Manhattan is most pronounced (most shallow) around Midtown, hence the clustering of highrises there. Obviously economic factors, transit, and location-location-location weigh heavily, but the overall effect over a long span has been influenced by this subterranean feature.

[Crawford]

Originally Posted by denizen467

IIRC the shallow bedrock in Manhattan is most pronounced (most shallow) around Midtown, hence the clustering of highrises there.

The highrise concentration in Midtown has nothing to do with bedrock. It's because the main transit hubs were built here (Penn, GCT, PABT, PATH, Subway), and because of early 20th century zoning changes, which restricted commercial to basically south of 60th Street.

As Manhattan developed, the commercial center gradually moved northward, with the desirability and value increasing as you moved further north. With a very early version of NIMBYism, commercial growth was eventually restricted to the area south of Central Park, so the largest growth was in this space.

[denizen467]

^ This doesn't disprove my claim, which I have heard on a couple different occasions, from people actually involved in putting up highrises there. Your statement does little to explain why luxury residential high-rises aren't more prevalent south of Midtown. Given the amount of money that a developer could make, especially considering the unobstructed views (look no further than the New Jersey towers just across the river), it would seem there is some extremely major obstacle to preventing a proliferation of taller towers in that area. Perhaps you are just too accustomed to things as they are and can't fathom a nyc different from the one you know. If you take a look at other skylines, like SF, Seattle, Chicago, Houston, etc., you'll see the occasional highrise standing alone in a low-rise neighborhood; that is the normal course of urban development. Zoning and nimbys may well be the explanation for what I am talking about, but you only referred to the area north of Midtown. If someone has further explanation I would be interested in seeing it.

[dave8721]

Speaking of narrow buildings on so-so foundations, here is a uber-thin nearly 600-footer on barrier island beach sand. And yes the prices of the lower floors units start at $3 million and go up from there.

Proposed "Unique" in Sunny Isles Beach:
http://i.imgur.com/bwRnF.jpg
(image from the exmiami guys)

[Crawford]

Originally Posted by denizen467

^ This doesn't disprove my claim, which I have heard on a couple different occasions, from people actually involved in putting up highrises there. Your statement does little to explain why luxury residential high-rises aren't more prevalent south of Midtown.

Again, it's because of zoning. The zoning doesn't allow the same FAR south of Midtown, and most of those areas are landmarked anyways. Even in non-landmarked parts, there are usually height restrictions.

Originally Posted by denizen467

^
Given the amount of money that a developer could make, especially considering the unobstructed views (look no further than the New Jersey towers just across the river), it would seem there is some extremely major obstacle to preventing a proliferation of taller towers in that area.

Do you know these areas? These are the best urban neighborhoods in the U.S. They will never allow huge towers in most parts of the Village/Soho/Flatiron/Chelsea/UnionSquare (yes, there are a few sections where you can build very tall, and developers already have built or are planning in those limited zones, but it will never look like Midtown, even if there are some scattered towers of significant height).

[woodrow]

Another factor is the size of blocks in Chicago and standard lot sizes, which allowed Chicago developers to more easily create large buildings sites, compared to NY.

[Crawford]

Originally Posted by woodrow

Another factor is the size of blocks in Chicago and standard lot sizes, which allowed Chicago developers to more easily create large buildings sites, compared to NY.

I don't think the blocks themselves have much to do with it, as most of Manhattan is on a regular grid, and large, blocky buildings are fairly typical.

[mhays]

Construction guy here. Yes, ground conditions are a big factor in what gets built...anything's possible but it all affects the spreadsheets. And yes, Chicago seems to have a prevalence of bigger sites vs. Manhattan. While I don't know Chicago's parking requirements, anecdotally there seems to be a lot of it with most buildings, and that's a big reason why larger sites pencil. Low/zero parking ratios (as well as use of conveyance systems etc.) is a defining factor in Manhattan's ability to use tiny sites.

[ardecila]

Originally Posted by mhays

Construction guy here. Yes, ground conditions are a big factor in what gets built...anything's possible but it all affects the spreadsheets. And yes, Chicago seems to have a prevalence of bigger sites vs. Manhattan. While I don't know Chicago's parking requirements, anecdotally there seems to be a lot of it with most buildings, and that's a big reason why larger sites pencil. Low/zero parking ratios (as well as use of conveyance systems etc.) is a defining factor in Manhattan's ability to use tiny sites.

Many of Chicago's skyscraper districts are former warehouse/industrial districts. The warehouses needed large floorplates, so the warehouse owners already did the work of consolidating multiple parcels into larger lots. In many cases the lots were bought and consolidated as soon as they were subdivided, so the sites were never occupied by single-lot development. Going north or south along the lakefront, the large lots continued, but in the form of mansions with large yards. Places like Downtown and Midtown NY have always been commercial and residential districts characterized by smaller lots and smaller building footprints, and the difficulties of acquiring contiguous parcels force developers to go skinnier and taller.

Foundations are a huge portion of the cost of a building, so soil conditions greatly influence what is possible to build. Zoning is irrelevant, since pretty much every major American downtown was built before the advent of zoning ordinances, and the zoning ordinances pretty much reflected the density of what was already built, even as it sought to shuffle land uses.

[mhays]

My city, Seattle, is an example where zoning is lower than what already exists in the core CBD. At least it's not what the voters passed in the late 80s, which limited projects to 485' I think, roughly half our tallest building. San Francisco is another example.

Those bigger lots are convenient for Chicago development. But I'd guess it's also a necessity to have sizeable lots in most cases due to parking and the non-stratospheric square foot prices. I'd be curious where parking is required now, and how much, since a lot of towers I saw had large amounts. Of course even a reasonable ratio means a lot is required when you have 600 units in one tower.

[ardecila]

Parking requirements are written into the Chicago zoning ordinance, but most large towers and even many medium-sized projects are done as Planned Developments, where pretty much every requirement is open for negotiation.

For as-of-right projects that don't go through PD, a 1:1 parking ratio is required, except in the densest zoning districts, where every unit after the first 100 can be parked at 0.6 spaces per unit.

The city recently passed a TOD ordinance to encourage developments with reduced or no parking near rail stations, but the applicable radius around each station is pretty small, leaving many obvious sites out of consideration for the parking reductions. Still, this has the potential to radically transform the city by making midrises financially feasible in outlying neighborhoods. The first of these projects is now under construction.

[mhays]

That's unfortunate. It makes really small sites impossible. And it hurts affordability.