[Cob] Roofing material?

[carmenkittiecat at aim.com]

Hello, have been away from the list for a while.

If anyone else has "The Hand Sculpted House" (Evans, Smith, Smiley), 
would you mind taking a look at something? On the second page of the 
full-colored photo pages, there is a photo of the Permaculture 
Institute of Northern California's office, and it says it was built by 
Penny Livingston, James Stark, and the Cob Cottage Company. Does anyone 
know what that roof is made of? At first glance while flipping through 
I thought it was a steel roof, but it looks kind of dull and has none 
of the ridges I'm used to seeing in any steel roofs I've come across. I 
Googled it but couldn't find a description, and I don't want to bug 
them just to ask what their roof is, especially if the answer is 
obvious (although I suppose they're my next stop!). It looks great and 
goes well with the cob visually, whatever it is. I would assume the 
PINC collects rainwater so I would expect whatever it is to be 
non-toxic as well. I'm quite interested in it, so any info would be 
very much appreciated.

Thanks,
Carmen Copeland Johnston
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