6.5.3 Criteria Common to Most or All Six Systems

• Except for retail space, at least some of the area occupied by the exterior building wall construction is excluded from any other type of measurement.
• Mechanical equipment penthouses (unenclosed space) are excluded from any space billed to a tenant except for the REBNY method. The other five systems deduct vertical penetrations for duct shafts, major plumbing and electrical chases, elevator shafts, and public exit stairs. All such costs must be amortized in the basic rental rates charged by the landlord.
• The dominant portion of the inside face of the exterior wall is the anchor point for all systems, although each system differs on exactly where that point is located.
• Core or loss factors (the percentage of the billable area of each floor that is not part of the tenant’s own space) are part of almost every lease negotiation. However, the factors are mentioned only briefly in two standards (REBNY and GWCAR). They are calculated in the new BOMA system but are not specifically mentioned.
• Private stairs, dumbwaiters, toilets, and kitchens are considered part of the rentable space.