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Cantilevered structures - how do they do that?

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txlibdem Donating Member (1000+ posts) Send PM | Profile | Ignore Wed Jun-15-11 10:07 PM
Original message
Cantilevered structures - how do they do that?
I am referring to at least one of the works of famed architect Frank Lloyd Wright:
http://www.fzarpelon.com/?p=197
http://www.archdaily.com/60022/ad-classics-fallingwater... /

Or perhaps similar to this, but with longer roof (but no walls as shown) to form a quasi-indoors/outdoors space that can be screened in or used with shade cloth to keep direct sun off the area.
http://www.homedesignhome.com/concrete-house-by-sergio-... /

My question is: How do they do that? I have a friend who is a structural steel engineer who will draw up the plans but I would still like to know the inner workings of what's behind the stucco, etc.

Does anyone have a "for dummies" type explanation of how such structures are made (and made strong enough to withstand high winds which we do get here).

Help or advice much appreciated!
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Stinky The Clown Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Jun-16-11 03:47 PM
Response to Original message
1. Here
http://www.pennridge.org/works/cantstruct.html

Visual clues as to how they work. No technical stuff.
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txlibdem Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Jun-16-11 05:34 PM
Response to Reply #1
2. Thanks for the link
It helped me visualize the different types of cantilevered structures.

I think I need to do more research to understand the "hidden" structural elements. I'm leaning toward a simplistic visualization: it's like a "T" shape with a support to hold the weight. But what keeps it from shifting over time or drooping when people stand right at the edge???
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Stinky The Clown Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Jun-16-11 06:55 PM
Response to Reply #2
3. The size of the members determine the strength of the structure.
Here's a cantilevered structure to consider.

http://www.grandcanyonskywalk.com/
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txlibdem Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Jun-16-11 09:40 PM
Response to Reply #3
4. Not even with a team of wild horses
There's no way you're gonna get me to go out onto that damn thing!

PS, the engineering link on that page was really informative
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Stinky The Clown Donating Member (1000+ posts) Send PM | Profile | Ignore Fri Jun-17-11 08:50 AM
Response to Reply #4
5. For some, the "mystery" of the cantilever is akin to the "mystery" of flight.
There is sound engineering and sound physics that underlie both.
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txlibdem Donating Member (1000+ posts) Send PM | Profile | Ignore Fri Jun-17-11 03:28 PM
Response to Reply #5
6. No mystery
Just fear of heights.

:hide:
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trud Donating Member (1000+ posts) Send PM | Profile | Ignore Fri Jun-24-11 09:11 PM
Response to Reply #3
12. wish they hadn't done that
nothing manmade modern should be in the canyon. (I know there are Indian structures, that's different.)
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txlibdem Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Jun-23-11 06:54 PM
Response to Original message
7. The question was really in relation to a roof overhang, how much extra support needed
Just a thought experiment at this point. If there were a 10 foot wide roof overhang that ran the entire length of a house, would one need to use 20 ft beams securely connected at both the inside end and the point where it connects to the exterior wall? Or would an even longer beam be needed to be structurally sound?

PS, we get high winds, torrential rains, hail and (rarely) tornadoes coming through these parts. I want to make a safe and sound structure but it's well over my head.
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Wash. state Desk Jet Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Jun-23-11 11:06 PM
Response to Reply #7
8. Are you saying the bump out is 10 feet?
like a car port ?
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txlibdem Donating Member (1000+ posts) Send PM | Profile | Ignore Fri Jun-24-11 06:58 AM
Response to Reply #8
9. Yes
But it's just a porch. Or would that be called a veranda?
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Wash. state Desk Jet Donating Member (1000+ posts) Send PM | Profile | Ignore Sat Jun-25-11 09:44 PM
Response to Reply #9
13. I gather the impression you are captivated with an idea.
Have you thought about simply tying into the house such as you would a deck and add posts for supports ? Or better yet throw a beam across and build away ? In other words yer tied in but also free standing .OK so you tie into the roof rafter tails with a 2by6 2by 8 what have you, place yer 4 by 4 posts under the 2-6 or 2by 8 and build away. The beam across may be a bit of a over kill . Free standing structure that is tied into the house is the idea.

Keep it in simple terms when you build .for example when I build second story decks-I will tie into the house but I add support posts where I tie it in-hence a free standing second story deck.A deck can cave in when there are too many people partying on it -or too much weight-, it's been known to happen, Usually a tie in will separate from the house-but if it had support post's properly installed and braced correctly such a thing cannot and will not happen -exception to a natural disaster such as severe earth quake.Free standing means self supporting.

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txlibdem Donating Member (1000+ posts) Send PM | Profile | Ignore Sat Jun-25-11 10:16 PM
Response to Reply #13
14. Thanks for the reply
Your impression is half right. My wife wants a 10' overhang along the entire south edge of the roofline and did not like the look of the posts: wants an unobstructed view of the yard.
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Wash. state Desk Jet Donating Member (1000+ posts) Send PM | Profile | Ignore Sun Jun-26-11 01:58 AM
Response to Reply #14
15. Well ,covered decks will tie in at the rafter tails
Edited on Sun Jun-26-11 02:04 AM by Wash. state Desk Jet
or in some cases rest on the shingle atop the roof. But ,you would still want to throw at least some 4by 4 supports starting with one on each end and from there find locations that will not obstruct her view. I think yer getting into quite the cost for what yer getting at and than there is the code issues.What is the length 10 ft. by what ? I can throw the thing on a program that shows how and what you need to do and what materials you will require. Tell me the state and I'll check the computer generated plans to yer codes.

on edit I see you know a engineer -! Hadn't thought about a steel frame !
You should go with wood ,save yerself a ton of money !
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Kolesar Donating Member (1000+ posts) Send PM | Profile | Ignore Fri Jun-24-11 11:47 AM
Response to Original message
10. Falling Water had shifted and made the windows unusable a few decades ago
I toured it in about 1990. I liked the fan fold cut lumber or veneer on one wall. I didn't find the design to be that impressive, overall. He built it over a stream and left a big piece of rock in the living room. So what?
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txlibdem Donating Member (1000+ posts) Send PM | Profile | Ignore Sun Jun-26-11 05:08 PM
Response to Reply #10
16. Wasn't that caused by ground subsidence more than failure of the structure?
I seem to recall seeing a documentary on Falling Water, it changed to new owners who renovated it and corrected some structural issues.

But, just to be clear, I have no intention of building anything over a creek or river; just want a cantilevered roof with no visible support beams.
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trud Donating Member (1000+ posts) Send PM | Profile | Ignore Fri Jun-24-11 09:09 PM
Response to Original message
11. I lived in a dorm that had a cantilevered part
the floor sloped...

just asking for trouble, imho.

I think Fallingwater is beautiful, but Wright's houses did have some problems.
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