[GSBN] Catalan vaulting

[Bob Theis]

It's not really about bales, but some of us have been grousing for years now that our wall systems are quite green but our roof systems  are   business as usual.  

Well,  Kim Thompson reminded me of a technique I loved while living in the depths of NYC, but forgot about when I got to California. And I've been talking it up since, so I decided to save myself some effort by posting an introduction here. 

Known variously as Catalan vaulting, timbrel vaulting, cohesive construction, or Guastavino vaulting, it's centuries old, had its heyday in the industrial world in the early 1900s, ( for the archinerds, Gaudi and McKim, Mead and White used it extensively ) and is so counterintuitive it still makes my head hurt. 

It's used to form vaults and domes,  and big ones, too.  Using several layers of thin flat tiles,  something like 6" x 12" x 3/4 - 1 " thick. Traditionally ceramic, but recently pressed soil cement has been used. 

The first layer gets installed using a gypsum mortar, buttered at the edges and tapped into place without any falsework under it ( ! )  This is possible because gypsum sets so fast. After the first layer has been extended out a few feet, it is followed with at least two additional layers laid with cement lime mortar, typically in diagonal courses to avoid joint alignment between layers.  Out into space it extends until you lock it all up at the apex. 

Impressive enough, but the astounding part is how fiendishly strong the finished product is.  The floor vaults created with it at places like the Boston Public Library ( McKim, Mead and White,  architects) are incredibly flat, with a rise to span like 1:10. I wish I had a copy of the photo my architectural  history professor showed, of a vault being demolished by a worker with a jackhammer standing on half a vault  cantilevered out about 15 feet. 

There's a revival of interest in the technique in academie,  and MIT is one of its hotbeds. They've set up several good websites, and http://www.guastavino.net/ is a good place to start.  Professors there have advised on the design of recent buildings, including one in very rural South Africa, which has a good photo album at http://picasaweb.google.co.uk/bellamyjk/BuildingInSouthAfrica#  ( Thanks to Kim for the link ) 

There are issues to address, of course, such as how best to insulate it, and whether it needs to be made more ductile for seismic regions. But it's handsome,  fireproof, rot proof and not based on sticks; that seems like a good place to start. 

Check it out. Tell Guastavino I sent you. 

Bob 
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