GSF: from exterior or centerline of walls?

From the official LEED Online v3 Help Content: "Gross square footage (GSF) --- Sum of the floor areas of the spaces within the building including basements, mezzanine and intermediate-floored tiers, and penthouses with headroom height of 7.5 ft or greater. It is measured from the exterior faces of exterior walls or from the centerline of walls separating buildings, but excluding covered walkways, open roofed-over areas, porches and similar spaces, pipe trenches, exterior terraces or steps, chimneys, roof overhangs, and similar features. --- Source: ANSI/ASHRAE Standard 90.1, ASHRAE.org" For LEED-CI, I would see that being the exterior face of the exterior walls and the centerline of any interior tenant walls. Since there are so many variations of how GSF is defined, I always send that definition around whenever I ask someone for their numbers. :)

Sorry - I referenced LEED-CI as you posted this on the LEED-CI page not the LEED-CS page. You are correct that for LEED-CS buildings, it would need to go to the exterior face of the walls (assuming that it is a stand-alone building and not an addition).