n. A shed used as an office or den or as the center of operations for a person or business.
The 1996 Ford Ranger he uses to haul trash is an icon on campus. So is the storage building that houses the school's physical plant. It started as a shed, so it became known as Prentice’s "shedquarters."
—Ed Grisamore, “Gris: Gentle giant makes his voice heard,” The Telegraph (Macon, GA), January 10, 2015
Miles Thomas spent two and a half years on the road with her camera making the film single-handed — "I joke that I haven't got any credits for the end of the film!" — and edited it in her garden shed ("the shedquarters").
—Susan Mansfield, “Interview: May Miles Thomas on searching for Glasgow’s soul,” The Scotsman (Edinburgh), February 21, 2013
The United States started personal shedquarters in earnest with Thomas Jefferson’s square brick garden pavilion at Monticello, where he studied and wrote in the glow of Virginia sunsets.
—Jonathan Foyle, “Shed your commute,” Financial Times (London), February 24, 2012
2005 (earliest)
About World Shedquarters
Purpose built for relaxation, a little work, drinking, watching Sky Sports, playing PS2.
—Dan Mesh, “World Shedquarters,”, September 06, 2005
If, after reading this article, you're interested in our club, please
call Lance… for more info, or you can write the Castle Corps
at the following address…:

CC Membership Officer
Castle Corps Shedquarters
180 Woodston Way
Ben Lomond, CA 95005
—Ken Laws, “Charter for an Interesting Club,” ba.general, March 11, 1993