BOMA Method A vs Method B Floor Allocation
How the two BOMA measurement methods differ in allocating shared floor areas to tenants, and when each method produces a higher or lower rentable area for a given suite.
Methodology
Method A allocates floor common areas to a single dominant tenant (or equally when no dominant tenant exists). It is simpler but can produce inequitable results on multi-tenant floors. Method B allocates floor common areas proportionally based on each tenant's usable area as a percentage of total usable area on the floor. This produces more equitable allocations on floors with multiple tenants of varying sizes.
BOMA 2017 vs 2024
The 2024 standard retains both methods but adds clearer guidance on when each is appropriate. Method A remains the default for single-tenant floors. Method B is now explicitly recommended for multi-tenant floors with significant shared corridors and restrooms. The 2024 update also clarifies that the choice of method should be consistent across all floors in a building.
Worked Example
A 20,000 SF floor has 2,000 SF of common area (corridors, restrooms, electrical). Tenant A has 12,000 SF usable, Tenant B has 6,000 SF usable. Under Method A (if Tenant A is dominant), Tenant A gets all 2,000 SF allocated — their rentable is 14,000 SF. Under Method B, Tenant A gets 12,000/18,000 × 2,000 = 1,333 SF (rentable 13,333 SF), and Tenant B gets 6,000/18,000 × 2,000 = 667 SF (rentable 6,667 SF).
Financial Impact
The difference between Method A and Method B can change a tenant's rentable area by 2-5% on a multi-tenant floor. For a 10,000 SF tenant paying $40/SF, a 3% difference represents $12,000 per year in additional rent and CAM charges.
Lease Implications
Leases should specify which BOMA method is used for measurement. When leases reference 'BOMA standard' without specifying the method, disputes arise at renewal. Landlords should ensure consistency between the measurement method in the lease and the method used for CAM allocation.
Common Errors
- Using Method A on a multi-tenant floor, unfairly burdening the largest tenant
- Switching methods between lease renewals without adjusting the rentable area in the lease
- Applying different methods to different floors in the same building
- Confusing floor common area allocation (Method A/B) with building common area allocation
Additional Context
Method A vs Method B is the most common source of BOMA measurement disputes in multi-tenant office buildings. The choice of method directly affects rentable square footage, which in turn affects both base rent and pro-rata CAM share calculations.
Related Resources
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