The space that is actually occupied by a tenant, typically equal to the size of the tenant’s suite, without deductions for columns or other structural elements. Useable square footage may differ from rentable square footage which accounts for a tenant’s share of common area.
For instance, an office tenant may occupy 25,000 useable square feet on a floor with 100,000 total useable square feet plus 10,000 square feet of corridors, bathrooms and other common areas. To calculate useable square footage in this case, there is a 10% floor common area factor (100,000 useable square feet plus 10,000 square feet common areas equals 110,000 rentable square feet divided by 100,000 useable square feet). Thus, the tenant may pay rent on 110% of their useable square footage, or 27,500 square feet in this case. Note that common area factors may apply to both individual floors as well as the building as a whole - this is known as the load factor. Office and retail properties often charge rent and/or charge CAM reimbursements based on rentable square footage as the tenants benefit from common space usage.