Usonian gabled roof magic

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arch
Posts: 3
Joined: Sun Oct 10, 2021 3:00 pm

Usonian gabled roof magic

Post by arch »

Hi

I’m a polish Usonian enthusiast and have discovered this cool architecture style fairly recently. I was wondering if you could lend me a bit of your expertise and help me with a conundrum that quite literally keeps me up at night.

I’m not an architect and have zero spacial imagination so please forgive me my ignorance and lack of vocabulary. Quite possibly my question has a quite obvious answer for anyone with a basic understanding of architecture and physics.

When I look at Zimmerman House or Alsop House or Eric Brown house or Schaberg house or Sweeton house I cannot understand how their gabled roofs work.

- there doesn’t seem to be any collar beams/ties in their trusts, which in a typical house hold a double pitched roof together

- significant parts of one gable seem to rest on a series of wooden window frames as if a giant joke on gravity (these sense of humor and seeming disregard to gravity's rules is present in a lot of Frank’s work and attracted me to him personally)

- there also doesn’t seem to be any lintel above the windows anywhere.

So how are those gabled roofs possible gravity wise?

The only thing I could deduct is that there are force imbalances embedded into those houses design where brick mass in walls bears most of the roof’s load, this allowing the other gable to “afford” less reinforcement. Is that a correct assumption?

Eg.

In Zimmerman, I guess it’d be the walls in the back of the living room room on one end and the carport storage on another. Also, the inner wall of the corridor “happens” to align perfectly with the roofs ridge as well. Plus the frameless garden windows are positioned in between brick pillars that also seem to be there to bear some load.


In Alsop the brick mass over the roof plane on one end seems to be a weight to hold the truss on one and release it slightly on another. The gallery wall also seems to align with the ridge above it.


As far as Eric Brown and Schaberg and Sweeton I have no idea.

I would greatly appreciate any insight/pictures into how this magic happens.

Using this occasion I would like to thank You all in this amazing community for a wonderful resource of all things Wright which I find extremely fascinating and useful as a new fan.

Thank You!

Tom
Posts: 3563
Joined: Sun Jan 30, 2011 7:53 pm
Location: Black Mountain, NC

Re: Usonian gabled roof magic

Post by Tom »

Welcome.
My guess is that you have some experience with construction because your questions don't strike me as typical of someone who is new to the work of Wright.
Personally, I've found that answering the type of questions you pose here is one of the real pleasures of Wright studies.
I compare it to looking under the hood of a car.
Before getting into this in any detail have you discovered the Avery Archives?
Using your detective skills and exploring these drawings you'll be able to find the answers to many of your questions.
The folk in this forum will also be happy to help and discuss:

https://findingaids.library.columbia.ed ... d_12471376

(BTW: I've been recently enjoying several detective mysteries set in Poland on Netflix.)

Tom
Posts: 3563
Joined: Sun Jan 30, 2011 7:53 pm
Location: Black Mountain, NC

Re: Usonian gabled roof magic

Post by Tom »

Although it doesn't answer any of your specific questions you might find this interesting:

viewtopic.php?f=2&t=14814&p=112688&hili ... se#p112688

Roderick Grant
Posts: 10995
Joined: Wed Mar 29, 2006 7:48 am

Re: Usonian gabled roof magic

Post by Roderick Grant »

Arch, I agree with Tom. You have set a heavy table to gorge on. It should inspire myriad responses from all corners.
Resident structural expert, DRN, owner of Sweeton will get into the thick of it, no doubt.

arch
Posts: 3
Joined: Sun Oct 10, 2021 3:00 pm

Re: Usonian gabled roof magic

Post by arch »

Thank You guys.

Detective process, when reverse engineering those details is a great way to put it Tom.

The link to the archives of the drawings helped me understand lots of engineering behind some of those details immensely.

Thank You!

DRN
Posts: 4182
Joined: Mon Jul 10, 2006 10:02 am
Location: Cherry Hill, NJ

Re: Usonian gabled roof magic

Post by DRN »

Hi arch.
The short answer to your question of how did Wright do it was, he didn't; at least for the Sweeton house. The Sweeton house was, in the words of my structural consultant, a slow motion collapse from the time it was constructed. The ridge was a doubled 2x6 spanning 28' from a concrete block wall to a piece of glass. The portion of the ridge adjacent to the masonry mass of the kitchen held up due to the bolstering of the masonry and some steel tie rods found when we removed the ceiling. The ridge portion that spanned from the masonry mass to the north gable wall sagged, causing the window wall to bow outward as can be seen in the photos. The opposite side of the house (toward the carport and entry) held as the rafters were flush framed to a steel channel seen in the photos in the third link below.

I went through the process of study, design, verification with the assistance of a structural engineer, documentation, and construction of repairs to the windowall and gable roof in 2014-2015. I documented the process on a long and winding Wright chat thread. Some highlights:

Initial discussion, before photos showing sagging and bowing, and structural concepts:
viewtopic.php?f=2&t=7523&hilit=sweeton+roof

My construction drawings:
viewtopic.php?f=2&t=7523&hilit=sweeton+roof&start=90
My solution was to make a series of moment frames at each of the mullions between the French door pairs by inserting steel flitch plates and gusset plates to tie the reinforced rafters to the new (continuous from slab to roof mullions). The ridge was reinforced with a 1" x 5.5" steel flitch plate from the gable wall to the masonry mass....a lot of steel was added.

Pictures of roof framing opened. aka. The part where a trailer load of steel is swallowed by the house:
viewtopic.php?f=2&t=7523&hilit=sweeton+roof&start=135
(of note, two tie rods were found anchoring the portion of the ridge that DIDN'T sag to a steel plate visible high on the interior of kitchen's masonry wall)

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