# What were the purpose of the "discolered" floors in the old WTC buildings? **URL:** \ **Category:** Factual Questions\ **Created:** [April 5, 2019, 10:24pm UTC](https://boards.straightdope.com/t/what-were-the-purpose-of-the-discolered-floors-in-the-old-wtc-buildings/832107 "2019-04-05T22:24:55Z")\ **Posts on this page:** 18\ **Page:** 1
**Author:** ![Orionizer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/orionizer/32/4442_2.png) [@Orionizer](https://boards.straightdope.com/u/Orionizer)\ **Post date:** [April 5, 2019, 10:24pm UTC](https://boards.straightdope.com/t/what-were-the-purpose-of-the-discolered-floors-in-the-old-wtc-buildings/832107/1 "2019-04-05T22:24:55Z")
What were the purpose of the “discolored” floors in the old WTC buildings? The dark areas about 1/3 and 2/3 of the way up them? ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [April 5, 2019, 10:31pm UTC](https://boards.straightdope.com/t/what-were-the-purpose-of-the-discolered-floors-in-the-old-wtc-buildings/832107/2 "2019-04-05T22:31:53Z")
> [@Orionizer](#): > > What were the purpose of the “discolored” floors in the old WTC buildings? The dark areas about 1/3 and 2/3 of the way up them? They were for [technical services](https://upload.wikimedia.org/wikipedia/commons/thumb/f/f7/World_Trade_Center_Building_Design_with_Floor_and_Elevator_Arrangment_m.svg/1280px-World_Trade_Center_Building_Design_with_Floor_and_Elevator_Arrangment_m.svg.png) instead of offices. Each section was topped by a “sky lobby” where people switched between local and express elevators. ---
**Author:** ![ZurBob](https://avatars.discourse-cdn.com/v4/letter/z/71e660/32.png) [@ZurBob](https://boards.straightdope.com/u/ZurBob)\ **Post date:** [April 5, 2019, 10:51pm UTC](https://boards.straightdope.com/t/what-were-the-purpose-of-the-discolered-floors-in-the-old-wtc-buildings/832107/3 "2019-04-05T22:51:58Z")
> [@Colibri](#): > > They were for [technical services](https://upload.wikimedia.org/wikipedia/commons/thumb/f/f7/World_Trade_Center_Building_Design_with_Floor_and_Elevator_Arrangment_m.svg/1280px-World_Trade_Center_Building_Design_with_Floor_and_Elevator_Arrangment_m.svg.png) instead of offices. Each section was topped by a “sky lobby” where people switched between local and express elevators. I don’t understand what the OP is referring to, but apparently you do. Would either of you please explain? ---
**Author:** ![friedo](https://avatars.discourse-cdn.com/v4/letter/f/8edcca/32.png) [@friedo](https://boards.straightdope.com/u/friedo)\ **Post date:** [April 5, 2019, 10:52pm UTC](https://boards.straightdope.com/t/what-were-the-purpose-of-the-discolered-floors-in-the-old-wtc-buildings/832107/4 "2019-04-05T22:52:46Z")
And “technical services” means they were full of air conditioners, water tanks, electrical switchgear, fire safety gizmos, and the like. IOW, mechanical floors. ---
**Author:** ![friedo](https://avatars.discourse-cdn.com/v4/letter/f/8edcca/32.png) [@friedo](https://boards.straightdope.com/u/friedo)\ **Post date:** [April 5, 2019, 10:54pm UTC](https://boards.straightdope.com/t/what-were-the-purpose-of-the-discolered-floors-in-the-old-wtc-buildings/832107/5 "2019-04-05T22:54:46Z")
> [@ZurBob](#): > > I don’t understand what the OP is referring to, but apparently you do. Would either of you please explain? [These things](https://upload.wikimedia.org/wikipedia/commons/thumb/c/c5/World_Trade_Center%2C_New_York_City_-_aerial_view_(March_2001).jpg/847px-World_Trade_Center%2C_New_York_City_-_aerial_view_(March_2001).jpg) ---
**Author:** ![kenobi\_65](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kenobi_65/32/13178_2.png) [@kenobi\_65](https://boards.straightdope.com/u/kenobi_65)\ **Post date:** [April 5, 2019, 10:55pm UTC](https://boards.straightdope.com/t/what-were-the-purpose-of-the-discolered-floors-in-the-old-wtc-buildings/832107/6 "2019-04-05T22:55:22Z")
> [@ZurBob](#): > > I don’t understand what the OP is referring to, but apparently you do. Would either of you please explain? Take a look at [this picture of the original towers](https://www.history.com/.image/ar_16:9%2Cc_fill%2Ccs_srgb%2Cfl_progressive%2Cg_faces:center%2Cq_auto:good%2Cw_768/MTU4MjgyMTU4MzcxMjUxNjE4/september-11-world-trade-53374593.jpg) – you can see darker horizontal “bands” on both towers, as the OP described. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [April 5, 2019, 11:13pm UTC](https://boards.straightdope.com/t/what-were-the-purpose-of-the-discolered-floors-in-the-old-wtc-buildings/832107/7 "2019-04-05T23:13:43Z")
> [@ZurBob](#): > > I don’t understand what the OP is referring to, but apparently you do. Would either of you please explain? As mentioned, look at any photo and you will see band of darker color on floors about 1/3 and 2/3 up (as well as near the bottom and at the top). ---
**Author:** ![motu](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/motu/32/259_2.png) [@motu](https://boards.straightdope.com/u/motu)\ **Post date:** [April 5, 2019, 11:33pm UTC](https://boards.straightdope.com/t/what-were-the-purpose-of-the-discolered-floors-in-the-old-wtc-buildings/832107/8 "2019-04-05T23:33:33Z")
The color difference is the service floors have no windows ---
**Author:** ![JWT\_Kottekoe](https://avatars.discourse-cdn.com/v4/letter/j/3ec8ea/32.png) [@JWT\_Kottekoe](https://boards.straightdope.com/u/JWT_Kottekoe)\ **Post date:** [April 6, 2019, 2:40pm UTC](https://boards.straightdope.com/t/what-were-the-purpose-of-the-discolered-floors-in-the-old-wtc-buildings/832107/9 "2019-04-06T14:40:44Z")
Elevators are only part of the answer, but I saw an interesting Nova program once about the problem of elevators in tall buildings. If you run all the elevators the full height of the building, and wish to maintain reasonable wait times, you have to keep putting in more and more elevators. Soon, a huge fraction of the floor space is devoted to elevators. The first solution to this is to introduce sky lobbies as mentioned above. The modern solution is to combine this with a control system in which you tell the system which floor you want to go to and let the computer figure out which elevator stops to pick you up. Apparently, this makes a big difference. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [April 6, 2019, 4:52pm UTC](https://boards.straightdope.com/t/what-were-the-purpose-of-the-discolered-floors-in-the-old-wtc-buildings/832107/10 "2019-04-06T16:52:17Z")
Or, of course, you can combine the two. Which is probably necessary anyway, to handle high-volume times (when a lot of people are going to or from their offices). ---
**Author:** ![cochrane](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cochrane/32/10441_2.png) [@cochrane](https://boards.straightdope.com/u/cochrane)\ **Post date:** [April 6, 2019, 5:44pm UTC](https://boards.straightdope.com/t/what-were-the-purpose-of-the-discolered-floors-in-the-old-wtc-buildings/832107/11 "2019-04-06T17:44:44Z")
They gave King Kong a better toehold when he climbed up the South Tower back in '76. 😃 ---
**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 6, 2019, 5:46pm UTC](https://boards.straightdope.com/t/what-were-the-purpose-of-the-discolered-floors-in-the-old-wtc-buildings/832107/12 "2019-04-06T17:46:28Z")
Some buildings have [double-decker elevators](https://en.wikipedia.org/wiki/Double-deck_elevator). ---
**Author:** ![panache45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/panache45/32/64_2.png) [@panache45](https://boards.straightdope.com/u/panache45)\ **Post date:** [April 7, 2019, 4:42am UTC](https://boards.straightdope.com/t/what-were-the-purpose-of-the-discolered-floors-in-the-old-wtc-buildings/832107/13 "2019-04-07T04:42:08Z")
> [@Dewey\_Finn](#): > > Some buildings have [double-decker elevators](https://en.wikipedia.org/wiki/Double-deck_elevator). The Eiffel Tower has those… plus, they have to travel in curves. ---
**Author:** ![ZurBob](https://avatars.discourse-cdn.com/v4/letter/z/71e660/32.png) [@ZurBob](https://boards.straightdope.com/u/ZurBob)\ **Post date:** [April 7, 2019, 12:02pm UTC](https://boards.straightdope.com/t/what-were-the-purpose-of-the-discolered-floors-in-the-old-wtc-buildings/832107/14 "2019-04-07T12:02:48Z")
> [@Orionizer](#): > > What were the purpose of the “discolored” floors in the old WTC buildings? The dark areas about 1/3 and 2/3 of the way up them? Thanks all, for the clarification. I was thinking “discolored” floors was perhaps in reference to um… something else. ---
**Author:** ![Hermitian](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hermitian/32/470_2.png) [@Hermitian](https://boards.straightdope.com/u/Hermitian)\ **Post date:** [April 8, 2019, 12:46pm UTC](https://boards.straightdope.com/t/what-were-the-purpose-of-the-discolered-floors-in-the-old-wtc-buildings/832107/15 "2019-04-08T12:46:53Z")
No one seems to be addressing the obvious question to me. Why make them look different? Plenty of tall buildings have service floors without making them stand out. Since keeping a uniform look with windows would not have been difficult, I am guessing they wanted them there to break up the exterior? Maybe they thought it looked too uniform? ---
**Author:** ![Kzbre5m](https://avatars.discourse-cdn.com/v4/letter/k/f08c70/32.png) [@Kzbre5m](https://boards.straightdope.com/u/Kzbre5m)\ **Post date:** [April 8, 2019, 2:50pm UTC](https://boards.straightdope.com/t/what-were-the-purpose-of-the-discolered-floors-in-the-old-wtc-buildings/832107/16 "2019-04-08T14:50:15Z")
The mechanical floors needed venting, of course, so they can’t be windows but a screen. Buildings gotta breathe from somewhere. The architect just made the whole floor that way instead of just sections. I found this: > [@](#): > > The darker ares of the towers were the mechanical floors on floors 7/8, 41/42, 75/76 and 108/109. These areas were darker since they had no windows. Instead there were black vents used for ventilation. Additionally, the columns were a bit wider (at the top it was more playful) creating these “bands” going around the building. Yamasaki did probably change the layout of the columns on the 108/109th floor simply for aesthetic purposes. [A few questions regarding design and structure of WTC | SkyscraperCity Forum](https://www.skyscrapercity.com/showthread.php?t=2006646) (first answer). The answer includes a photo showing what’s behind the column facade. ---
**Author:** ![jjakucyk](https://avatars.discourse-cdn.com/v4/letter/j/3d9bf3/32.png) [@jjakucyk](https://boards.straightdope.com/u/jjakucyk)\ **Post date:** [April 8, 2019, 2:53pm UTC](https://boards.straightdope.com/t/what-were-the-purpose-of-the-discolered-floors-in-the-old-wtc-buildings/832107/17 "2019-04-08T14:53:38Z")
> [@Hermitian](#): > > Why make them look different? Plenty of tall buildings have service floors without making them stand out. In a lot of cases they do stand out, but the designs use that difference architecturally as part of the rhythm of the building. In the case of WTC, it looks like they simply swapped out the windows for vents/louvers, which are darker and don’t reflect light the same way as glass does. That’s more a case of “it is what it is.” ---
**Author:** ![Orionizer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/orionizer/32/4442_2.png) [@Orionizer](https://boards.straightdope.com/u/Orionizer)\ **Post date:** [April 8, 2019, 7:40pm UTC](https://boards.straightdope.com/t/what-were-the-purpose-of-the-discolered-floors-in-the-old-wtc-buildings/832107/18 "2019-04-08T19:40:29Z")
Thanks for the info, everyone!