The roof over Kentuck Knob

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Tom
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Re: The roof over Kentuck Knob

Post by Tom »

Image

Can't figure out how to get the image from ArtStor in to this post but they have a roof framing plan of Hagan showing big steel in the living room roof. At the end the plan shows three pieces of steel connecting to the main ridge steel and fanning out to the perimeter. What two of those beams are resting on beats me.

Tom
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Re: The roof over Kentuck Knob

Post by Tom »

Reviewing back thru some of the posts it seems the perimeter lintel might have some steel as well and so those beams that seem to be hanging in air are probably sitting on those.

Wright seems to be going out of the way to contradict expectations and increase the effect of drama. It certainly pays off inside looking thru the end of the living room glass.
Last edited by Tom on Wed Jun 09, 2021 4:08 pm, edited 2 times in total.

SDR
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Re: The roof over Kentuck Knob

Post by SDR »

An alternative to posting an image found online is to provide a link to that image. You can start with the Artstor Hagan file:

https://library.artstor.org/#/search/Wr ... =1;size=48

then give either the image number (5) or the URL of that page: https://library.artstor.org/#/asset/286 ... 3000332548

S

Tom
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Re: The roof over Kentuck Knob

Post by Tom »

Thank you
I’m out of practice.

Looks like the stone pier at the living room end just off center of the ridge line supports a flitch beam that carries the steel.
This is the kind of stuff that drove Phillip Johnson crazy. I can hear him now: “no fair! You can’t do that!”

Tom
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Re: The roof over Kentuck Knob

Post by Tom »

… wait, might be wrong. I’m using my phone but looks like that flitch beam misses the pier.

SDR
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Re: The roof over Kentuck Knob

Post by SDR »

Looking at architectural drawings ON YOUR PHONE ?? Are you mad, man ?

:roll:

https://www.youtube.com/watch?v=t2IXL9gYCAo

Tom
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Re: The roof over Kentuck Knob

Post by Tom »

…. Well it’s not ideal
But just realized that the bearing conditions of all three of those beams are detailed in the right hand margin of the sheet. So far I cannot understand them.
It’s a shame the resolution is not enough to be able to read the notes.

Tom
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Re: The roof over Kentuck Knob

Post by Tom »

Ok - so the long ridge steel in the living room roof terminates in the fireplace on the east end.
On the west end that beam terminates at detail 'N'.
From detail 'N' three beams fan out to detail 'M' at 11 o'clock, 'L' at 9 o'clock and 'O' at 7 o'clock.
Wondering if we could find a shot showing what the interior at 'O' looks like?
I think for sure the steel beam at 'O' is right online with a mitered glass corner window.

SDR
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Re: The roof over Kentuck Knob

Post by SDR »

If that's the case, header beams over the windows, meeting above the mitered glass corner, would carry the descending hip beam ? Are such headers shown as steel ?

https://www.theartblog.org/2019/05/visi ... nsylvania/

S

Tom
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Re: The roof over Kentuck Knob

Post by Tom »

I went back through the large PDF from Carnegie Mellon.

1.) From what I could tell from the not all that clear work there - there is a large continuous steel channel around the southern and western perimeters.
2.) The three steel beams that fan out in the original framing plan exist as 2-2x8's.
3.) The large steel Ibeam of the original drawing exits as a long 2-2x12 w/ 1/4" flitch plate.
4.) There is a construction photograph showing the large steel-T's in place along the south wall.

So in terms of the detail at 'O' that beam is easily supported by the steel channel above large steel-T's.
What is curious to me from the Carnegie Mellon screenshot (below) is the function of the small steel tube.
Have no idea is that is continuous or existing only at the mullions.


https://www.flickr.com/photos/54449844@ ... ateposted/

SDR
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Re: The roof over Kentuck Knob

Post by SDR »

All right---you've drawn me in. Now where does the Carnegie Mellon drawing come from ? Is that a depiction of the as-built condition ?

Compare to the roof framing sheet I linked above, and to another Artstor sheet showing building sections https://library.artstor.org/#/asset/286 ... 3206749936 The problem of keeping the rafters from spreading and the ridge sinking is dealt with forthrightly on that sheet by means of a horizontal tie below the ridge, creating a flat at the center of the ceiling. On the Carnegie Mellon sheet, the problem is managed more subtly and ingeniously---if perhaps less surely---by lowering the pitch of the ceiling relative to roof pitch, to make room for a horizontal tie immediately below the ridge beam. None of this appears on the Artstor sheet; the ridge is a hefty I-beam, and the beams "fanning out" (I suppose you mean the hip ridges) are also major steel members. I guess the connections of these members at the end of the ridge is supposed to provide the same resistance to spread that the ridge ties do---but it relies on that resistance being transferred from the terminus of the room, where the hip ridges descend, along the entire length of the window wall(s) via the box beam ?

The Artstor (Taliesin) drawing was revised twice, over the span of a year, yet it doesn't reflect what is found on your Carnegie Mellon sheet.

As to how the trellis is supported, and the window wall kept in line, the horizontal steel box beam presumably attends to the latter---perhaps continuous plywood screwed to the underside of the trellis soffit would have sufficed ? Meanwhile, the 2x6 outriggers supporting the trellis continue indoors, reduced to 2x4 to make the light shelf more slender in profile; surely they would support that shelf without the little steel angle that's added to them (and perhaps welded to the box beam ?)---it would seem to me. But what do I know ? (In the earlier drawing, the outriggers are paired 2x6s sandwiching a single 2x4 for the interior light shelf.)

I don't understand what the tall 1/4" steel channel is doing, at the wall line: doesn't the architect trust his hefty reinforced concrete continuous footing beneath that window wall ? (in the earlier drawing there is 3/4" plywood in place of the channel.)

The trellis has got a lot of wood in it---plenty evident in photos of same, confirmed by the section drawings. Maybe it plays see-saw with the weight of the roof, countering it by means of the "bent" that is the entire rafter-outrigger-trellis construction, the fulcrum being the window wall ? No wonder there are steel posts at that point ? Never has the triangle formed by the rafter-outrigger-post nexus been more useful ! And this see-saw is able to counter the tendency of the ridge to sink, to the point where the minimal rafter tie at the ridge is enough to do the job . . .

The trellis, rather than being a burden on the roof structure, is a vital part of same ?

S

Tom
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Re: The roof over Kentuck Knob

Post by Tom »

In July 2015 on page 3 of this thread you found and posted a large pdf from Carnegie Mellon. That link is still active and my screen shot comes from that.

As far as I can tell the Carnegie Mellon work is an analysis of as built conditions, but that does not seem to be made explicitly clear. Yet if so it represents an unusual case where the Taliesin drawings called for more steel than the contractor put in!

What you say about the possible uplift on the ridge due to the downshift motion of the trellis overhang is intriguing. We’ll probably never know if they thought it through to that degree. But I would be surprised if they didn’t. At this point in Wrights career that kind of balancing act was probably very very basic although it always strikes me as surprising.

One thing that does come across from reading some of the text in the PDF goes to Wrights personal involvement with this house after he designed it. I get the feeling it wasn’t much.
When the Hagans received the plans they asked him if it was on budget and he is said to have replied, “I have no idea.” He saw the house only once on a side trip from EJ Kaufman’s funeral. The house was only complete to the floor level, no walls or roof. The 50’s were a crazy busy decade for him and yet I think it’s one of his best houses.

Anybody know who the on-site apprentice was? Does the name ‘Key’ ring any bells?
Last edited by Tom on Tue Jun 08, 2021 11:04 pm, edited 3 times in total.

SDR
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Re: The roof over Kentuck Knob

Post by SDR »

I wonder if the switch from heavy steel in the roof, there to provide rigidity to the gable and to support the trellis, was done away with when it occurred to someone (presumably the architect) that the whole could be lightened if the weight of the trellis was taken advantage of . . .

In place of all the many definitions of "organic architecture" given by Mr Wright (and others, attempting to interpret him), I would gladly settle for the hidden-in-plain-sight structural "continuity" found at Hagan, assuming that the above interpretation is the correct one.

Heh---I do repeat myself---from six years and one page ago---and also forget that Roderick perceived much of what I lately (re)discovered, about the roof structure.

S

Tom
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Re: The roof over Kentuck Knob

Post by Tom »

The trellis is definitely rotating the roof rafter clockwise.
The collar tie is also definitely doing work, maybe in this case the opposite of what it is conventionally intended to do.

SDR
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Re: The roof over Kentuck Knob

Post by SDR »

Heh. I suppose. My idea of continuity would be for a steel V or boomerang, bolted to the rafters at the apex, would penetrate a continuous wide-flange ridge though openings in its web. Not that hard to accomplish, really, with the openings cut in the shop . . .?

S

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