Background:
Building originally built as hospital with full 11th floor (18,000 interior SF) penthouse below roof level. Floor originally housed mechanical equipment to serve 10th floor surgery. Building has been converted to office use and all mechanical equipment that supported surgery (and surgery) removed. Remaining floor contains top of shaft elevator machine rooms and (1) stair, and is otherwise empty. Developer plans to extend elevator service and additional stairs to floor and convert to lease space in 1-2 years. Currently developer proposes that entire floor be considered building service area in lease calculations.

Question 1:
Should the SF (other than elevator and stair) be considered "interstitial space" since it is not available for general occupancy due to it having a lack of provisions for egress, and be excluded from the IGA? Elevator machine rooms would be considered building service area and stair considered a vertical penetration.

Question 2:
If SF is considered building service area; when occupant area of "0" and building service of "18,000" is entered in spreadsheet, I get errors. How is this handled?