Rentable/Usable Load Factor (BOMA)
Why rent per rentable SF understates the cost of the space you use: office rent is quoted per RENTABLE SF, but a tenant only occupies the USABLE SF -- the rentable figure adds the pro-rata share of lobbies, corridors, and restrooms that cannot hold a desk. rentable = usable x (1 + common_area_factor); load_factor = rentable/usable; cost_per_usable = base_rent x load_factor. 10,000 usable SF at a 15% factor and $30/rentable-SF is 11,500 rentable SF -> $345,000/yr, and $34.50 per USABLE SF (15% above the quoted $30); a 20%-factor tower suite is $36.00/usable SF, $1.50 more for identical space. A cost-comparison aid; the measured BOMA areas and the lease govern.
Formula and source
rentable = usable x (1 + common_area_factor); load_factor = rentable / usable; annual_rent = base_rent x rentable; cost_per_usable = base_rent x load_factor.
BOMA rentable/usable load factor (the ANSI/BOMA Z65.1 Office Standard), by name; the measured BOMA areas and the lease govern.
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