Rentable/Usable Load Factor (BOMA)
Why rent per rentable SF understates the cost of the space you use.
Example
You enter
- Usable (occupiable) area (SF) 10000
- Common-area (add-on) factor (decimal, 0.15 = 15%) 0.15
- Quoted base rent ($/rentable SF/yr) 30
You get
- Rentable area (load factor) 11500
- Load factor 1.15
- Effective cost per USABLE SF $34.5
Checked against published worked examples from: CARR.
Details, formula, and sources
ScopeOffice 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 or tablerentable = usable x (1 + common_area_factor); load_factor = rentable / usable; annual_rent = base_rent x rentable; cost_per_usable = base_rent x load_factor.
Source and editionBOMA rentable/usable load factor (the ANSI/BOMA Z65.1 Office Standard), by name; the measured BOMA areas and the lease govern.
Free accessThe rentable/usable load-factor relation is a standard commercial-real-estate calculation; the usable area and common-area factor come from the BOMA measurement and the building.
What governsEstimate. AHJ and licensed professional govern.
API field namesusable_sf, common_area_factor, base_rent, rentable_sf, load_factor, cost_per_usable
- Rentable includes common rentable adds the pro-rata share of building common areas the tenant cannot occupyANSI/BOMA Z65.1
- Cost per usable the real cost of usable space is the quoted rate times the load factorBOMA convention
- Conventions vary add-on and loss-factor conventions vary; the measured BOMA areas governANSI/BOMA Z65.1