# Building a skyscraper - how do you remove the last crane? **URL:** \ **Category:** Factual Questions\ **Created:** [April 1, 2011, 12:30am UTC](https://boards.straightdope.com/t/building-a-skyscraper-how-do-you-remove-the-last-crane/576701 "2011-04-01T00:30:58Z")\ **Posts on this page:** 16\ **Page:** 2
**Author:** ![Joey\_P](https://avatars.discourse-cdn.com/v4/letter/j/919ad9/32.png) [@Joey\_P](https://boards.straightdope.com/u/Joey_P)\ **Post date:** [April 3, 2011, 1:35am UTC](https://boards.straightdope.com/t/building-a-skyscraper-how-do-you-remove-the-last-crane/576701/21 "2011-04-03T01:35:54Z")
> [@Fiendish\_Astronaut](#): > > How will they get this one down? I don’t think the explanations above cover it (not in my mind anyway): > > [The Shard | Aurelien Guichard | Flickr](http://www.flickr.com/photos/aguichard/5319980202/) I can see two options with that. One way is to lift it off with a helicopter, based on the budget that building has, that’s probably how they’ll do it. The other option is to dismantle it and lower it down through the center, possibly abandoning the last parts of it on the roof. ---
**Author:** ![Dewey\_Finn](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dewey_finn/32/4222_2.png) [@Dewey\_Finn](https://boards.straightdope.com/u/Dewey_Finn)\ **Post date:** [April 3, 2011, 1:37am UTC](https://boards.straightdope.com/t/building-a-skyscraper-how-do-you-remove-the-last-crane/576701/22 "2011-04-03T01:37:32Z")
> [@TriPolar](#): > > I don’t think this applies to the crane in that picture, but I once watched a building being erected, not too big, less than 10 stories, and the tower for the crane was located in the center where the elevator shafts were. I heard it said by several people that the tower actually became the structure for the elevator shaft, but I have no way to confirm that. I did see them remove the horizontal part of the crane, disassemble it into a few large pieces that were lowered to the ground using a small crane (basically a winch on a short beam attached to the roof somehow). There was no sign of the tower being removed, but it could have been disassembled internally out of view. On some buildings I’ve seen, that small crane you mentioned (“winch on a short beam attached to the roof somehow”) is used for supporting the platform used by the window washers, and is stored permanently on the roof. ---
**Author:** ![Jinx](https://avatars.discourse-cdn.com/v4/letter/j/c6cbf5/32.png) [@Jinx](https://boards.straightdope.com/u/Jinx)\ **Post date:** [April 3, 2011, 2:15am UTC](https://boards.straightdope.com/t/building-a-skyscraper-how-do-you-remove-the-last-crane/576701/23 "2011-04-03T02:15:03Z")
The same could be asked…how does the first crane go up? These things are modular, but what lifts the modular pieces into place to begin with? I assume a helicopter is the only answer. ---
**Author:** ![Cat\_Whisperer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cat_whisperer/32/4839_2.png) [@Cat\_Whisperer](https://boards.straightdope.com/u/Cat_Whisperer)\ **Post date:** [April 3, 2011, 3:49am UTC](https://boards.straightdope.com/t/building-a-skyscraper-how-do-you-remove-the-last-crane/576701/24 "2011-04-03T03:49:08Z")
> [@Dread\_Pirate\_Jimbo](#): > > Cat Whisperer’s hubby in to make some comments from the perspective of someone who has worked on several projects involving tower crane erection and dismantle… > > The piece on tower erection is a reasonably accurate description of “centre climbing” the mast. As also noted by **RadicalPi** , basically, you separate the mast and insert a new section to grow it taller and then pull those sections out as you take the crane down. This is fairly common and routine for erection and disassembly of a crane that has been placed outside the footprint of the structure it is building. If, however, the crane is placed inside the footprint of the building, this isn’t possible during the teardown, since the upper sections of the crane will no longer fit into the building as the crane gets lowered. So another solution is needed. > > But let me start at the start. Pretty much without exception, the crane is initially assembled using a mobile crane which stacks the mast and jib to as high as the project initially requires it to be. Mobile cranes can reach quite a staggeringly high distance in some cases, so you can build quite a tall tower crane right from the ground. If there is never a need to extend the height of the tower crane, of course this will also be the way the crane comes back down once it is no longer needed. [Here’s a pic](http://i32.photobucket.com/albums/d24/Calgaryjimbo/Rotationof2007-07-16005.jpg) from one of my former jobs, back in 2007, of a mobile crane putting up a mast for one of the tower cranes that was used on the project. The video in **Joey P** ’s post above also shows the dismantle process beautifully. > > In cases where it is decided to build the crane inside the footprint of the building, the typical way to raise the crane is by jacking it up. Once the building’s height has caught up to the minimum operating height of the crane, a heavy duty jacking system mechanically raises the whole kit ‘n’ kaboodle a few stories, then resets it at that that new height. This is what has been done with the cranes on The Bow tower in the OP. In the case of The Bow, when it comes time to take down a tower, the tallest crane will be used to dismantle and lower the jib pieces and then extract the pieces of the mast bit by bit from the building itself. When only the final tower crane is left, there are two options to take it apart: either use a helicopter to pick the pieces and bring them down as suggested by **dolphinboy** , which is very risky but sometimes makes sense, or build a temporary davit arm on the roof of the building tall enough to pick the jib and then the mast pieces. As the davit arm is typically assembled with the help of the tower crane it just helped take down, another smaller davit arm must then be put up to take the first one down, and so on until all the construction parts are gone. > > Putting up or taking down a tower crane is a surprisingly quick operation, typically requiring anywhere from a half day to two days, so they do seem to appear out of thin air and disappear just as quickly. But I have to say, I never get bored watching the process happen – it’s really cool! 🙂 So - kicking it off the side is the last choice? 😃 ---
**Author:** ![Dread\_Pirate\_Jimbo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dread_pirate_jimbo/32/3897_2.png) [@Dread\_Pirate\_Jimbo](https://boards.straightdope.com/u/Dread_Pirate_Jimbo)\ **Post date:** [April 3, 2011, 4:54am UTC](https://boards.straightdope.com/t/building-a-skyscraper-how-do-you-remove-the-last-crane/576701/25 "2011-04-03T04:54:29Z")
> [@Fiendish\_Astronaut](#): > > How will they get this one down? I don’t think the explanations above cover it (not in my mind anyway): > > [The Shard | Aurelien Guichard | Flickr](http://www.flickr.com/photos/aguichard/5319980202/) > [@Joey\_P](#): > > I can see two options with that. One way is to lift it off with a helicopter, based on the budget that building has, that’s probably how they’ll do it. The other option is to dismantle it and lower it down through the center, possibly abandoning the last parts of it on the roof. > [@Dewey\_Finn](#): > > On some buildings I’ve seen, that small crane you mentioned (“winch on a short beam attached to the roof somehow”) is used for supporting the platform used by the window washers, and is stored permanently on the roof. > [@Jinx](#): > > The same could be asked…how does the first crane go up? These things are modular, but what lifts the modular pieces into place to begin with? I assume a helicopter is the only answer. To answer all your questions at once, that crane, which is a “luffing crane,” is exactly like the ones in the OP and will be taken apart using a big-ass temporary davit arm system put up on the roof of the tower. A davit arm is that “winch on a short beam” that is usually found on building roofs to raise and lower swingstages for the window cleaners. The luffer has a jib that can be raised and lowered to bring the load closer or farther away from the structure, which is slower than a typical tower crane, but much more versatile. When they take it apart, the jib will be lowered to horizontal and dismantled section-by-section by workers using the davit arm to grab and lower the pieces, after which the mast will be taken apart the same way. No parts will be left in the building – these cranes are worth a fortune and just leaving pieces behind is simply not an option. The helicopter option is used infrequently, for a number of reasons. First, hooking up the parts and releasing them takes a lot of time and hovering the chopper in a completely stationary position for that long costs a ton in fuel. Second, if anything goes wrong – the load becomes unstable, a sudden wind comes up, the pilot really has to pee – the required operating procedure for the pilot is to cut the load free and save the helicopter. And dropping a couple thousand pounds of steel onto a downtown street or neighboring building from a dozen or more stories up results in a TON of follow-up paperwork, which is very inconvenient. Finally, as I noted above, to initially erect one of these cranes, it is typically done right at ground level, using a mobile crane, to get the tower its initial hundred feet or so of height, after which it is raised, using one of the methods I noted earlier, as they build the structure up around it. 🙂 ---
**Author:** ![Dread\_Pirate\_Jimbo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dread_pirate_jimbo/32/3897_2.png) [@Dread\_Pirate\_Jimbo](https://boards.straightdope.com/u/Dread_Pirate_Jimbo)\ **Post date:** [April 3, 2011, 4:56am UTC](https://boards.straightdope.com/t/building-a-skyscraper-how-do-you-remove-the-last-crane/576701/26 "2011-04-03T04:56:15Z")
> [@Cat\_Whisperer](#): > > So - kicking it off the side is the last choice? 😃 Yeah, that method requires a call to OSHA to report it and a bunch of paperwork that no one wants to do. Major hassle! 🆒 ---
**Author:** ![RadicalPi](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/radicalpi/32/9806_2.png) [@RadicalPi](https://boards.straightdope.com/u/RadicalPi)\ **Post date:** [April 3, 2011, 4:57am UTC](https://boards.straightdope.com/t/building-a-skyscraper-how-do-you-remove-the-last-crane/576701/27 "2011-04-03T04:57:19Z")
> [@Dread\_Pirate\_Jimbo](#): > > Cat Whisperer’s hubby in to make some comments from the perspective of someone who has worked on several projects involving tower crane erection and dismantle… > > The piece on tower erection is a reasonably accurate description of “centre climbing” the mast. As also noted by **RadicalPi** , basically, you separate the mast and insert a new section to grow it taller and t > Putting up or taking down a tower crane is a surprisingly quick operation, typically requiring anywhere from a half day to two days, so they do seem to appear out of thin air and disappear just as quickly. But I have to say, I never get bored watching the process happen – it’s really cool! 🙂 Thanks for the details! ---
**Author:** ![The\_Second\_Stone](https://avatars.discourse-cdn.com/v4/letter/t/bbe5ce/32.png) [@The\_Second\_Stone](https://boards.straightdope.com/u/The_Second_Stone)\ **Post date:** [April 13, 2013, 6:18am UTC](https://boards.straightdope.com/t/building-a-skyscraper-how-do-you-remove-the-last-crane/576701/29 "2013-04-13T06:18:15Z")
> [@thelabdude](#): > > Ah, others that remember Mike Mulligan. We’re nothing if not neat and square. ---
**Author:** ![gaffa](https://avatars.discourse-cdn.com/v4/letter/g/e68b1a/32.png) [@gaffa](https://boards.straightdope.com/u/gaffa)\ **Post date:** [April 13, 2013, 6:21am UTC](https://boards.straightdope.com/t/building-a-skyscraper-how-do-you-remove-the-last-crane/576701/30 "2013-04-13T06:21:59Z")
> [@cranecrews](#): > > we removed our one at work today, i made a step by step how we removed the tower crane along with 33 photos, if you like it please leave a message. I will be putting one up next on how we install a tower crane (a bit of the same really just in oppisite order :/) as well as how we service the tower crane. > enjoy > > [http://www.cranecrews.com/1/post/2013/04/removal-of-tower-crane.html](http://www.cranecrews.com/1/post/2013/04/removal-of-tower-crane.html) Cool, thanks for sharing that. I found [a better animation for the self-erecting type.](http://youtu.be/L50pDS9OGjw) ---
**Author:** ![Bullitt](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bullitt/32/5725_2.png) [@Bullitt](https://boards.straightdope.com/u/Bullitt)\ **Post date:** [April 13, 2013, 11:26am UTC](https://boards.straightdope.com/t/building-a-skyscraper-how-do-you-remove-the-last-crane/576701/31 "2013-04-13T11:26:23Z")
Guys, what’s with the zombie thread resurr-erections? Military chinstraps… now cranes. ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [April 13, 2013, 2:07pm UTC](https://boards.straightdope.com/t/building-a-skyscraper-how-do-you-remove-the-last-crane/576701/32 "2013-04-13T14:07:19Z")
zombies or no i thought cranes could fly. ---
**Author:** ![The\_Second\_Stone](https://avatars.discourse-cdn.com/v4/letter/t/bbe5ce/32.png) [@The\_Second\_Stone](https://boards.straightdope.com/u/The_Second_Stone)\ **Post date:** [April 13, 2013, 7:20pm UTC](https://boards.straightdope.com/t/building-a-skyscraper-how-do-you-remove-the-last-crane/576701/33 "2013-04-13T19:20:57Z")
> [@johnpost](#): > > zombies or no > > i thought cranes could fly. Cranes can fly. [Crane (bird) - Wikipedia](http://en.wikipedia.org/wiki/Crane_%28bird%29) ---
**Author:** ![Bullitt](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bullitt/32/5725_2.png) [@Bullitt](https://boards.straightdope.com/u/Bullitt)\ **Post date:** [April 13, 2013, 8:31pm UTC](https://boards.straightdope.com/t/building-a-skyscraper-how-do-you-remove-the-last-crane/576701/34 "2013-04-13T20:31:28Z")
Well, okay, maybe… but Ichabod Crane cannot fly. ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [April 13, 2013, 8:51pm UTC](https://boards.straightdope.com/t/building-a-skyscraper-how-do-you-remove-the-last-crane/576701/35 "2013-04-13T20:51:54Z")
> [@echo7tango](#): > > Guys, what’s with the zombie thread resurr-erections? Military chinstraps… now cranes. This a good zombie. Expert shows up with good, if not better cites and explanations. I have an ATMB coming up on this thread… ETA: maybe Frasier can. ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [April 14, 2013, 1:44am UTC](https://boards.straightdope.com/t/building-a-skyscraper-how-do-you-remove-the-last-crane/576701/36 "2013-04-14T01:44:22Z")
> [@thelabdude](#): > > Ah, others that remember Mike Mulligan. [A once proud man, he spends the rest of his days in darkness, living in a cellar, doing menial work, surrounded by his guilt and Mary-Anne’s twisted, deformed remains.](http://www.youtube.com/watch?v=-Z1R5vDG2Tg) ---
**Author:** ![Marley23](https://avatars.discourse-cdn.com/v4/letter/m/45deac/32.png) [@Marley23](https://boards.straightdope.com/u/Marley23)\ **Post date:** [April 30, 2013, 11:16pm UTC](https://boards.straightdope.com/t/building-a-skyscraper-how-do-you-remove-the-last-crane/576701/37 "2013-04-30T23:16:59Z")
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