Storage Area Classification and Measurement
How BOMA standards classify storage areas in commercial buildings, including in-suite storage, building storage rooms, and below-grade storage, and their treatment in rentable area calculations.
Methodology
In-suite storage closets and rooms are measured as part of the tenant's usable area at full value. Assigned storage rooms outside the tenant's suite (e.g., basement storage cages) are measured separately and may be included in the tenant's rentable area as a supplemental allocation. Building storage rooms serving the building's operation (cleaning supplies, maintenance equipment) are classified as building common area.
BOMA 2017 vs 2024
BOMA 2024 refines storage area classification by distinguishing between tenant-exclusive storage within a suite (included in usable area), assigned storage outside the suite (allocated as a supplemental area), and building storage rooms (building common area). The 2017 standard was less precise about assigned storage outside a tenant's premises.
Worked Example
A tenant has 5,000 SF usable area including a 100 SF in-suite storage closet. They also have an assigned 200 SF basement storage cage. The in-suite storage is already in the 5,000 SF usable. The basement cage adds 200 SF as a supplemental allocation. If the building load factor is 1.15, the tenant's total rentable = (5,000 × 1.15) + 200 = 5,950 SF.
Financial Impact
Storage area misclassification typically affects 1-2% of a tenant's rentable area. The larger financial impact comes from whether storage rent is charged at full office rates or discounted storage rates, a difference that can be $15-30/SF in urban markets.
Lease Implications
Leases should clearly define which storage areas are included in the premises, whether storage is measured separately or included in the suite's usable area, and the rental rate applicable to storage space. CAM reconciliation should specify whether storage areas are included in the tenant's pro-rata share denominator.
Common Errors
- Measuring assigned storage at the building load factor instead of at actual size
- Classifying building maintenance storage as assignable to tenants
- Failing to include in-suite storage in usable area measurements
- Inconsistent treatment of storage mezzanines in warehouse/industrial buildings
2026 Review Controls for BOMA-Driven CAM Math
BOMA measurement changes affect CAM only when the lease, rent roll, or reconciliation denominator accepts the measured area. Confirm the measurement source before changing tenant shares.
- Record the BOMA standard version used for the rent roll and lease abstract.
- Compare tenant RSF, building RSF, and load factor against the reconciliation denominator.
- Flag non-allocated tenant areas separately so they are not loaded twice.
- Keep the measurement certificate or architect worksheet with the CAM support file.
- Document whether the lease allows remeasurement to change existing tenant shares.
Additional Context
Storage area disputes are increasing as landlords convert underutilized basement and mechanical spaces into revenue-generating storage. The classification of these converted spaces (as tenant usable, supplemental, or building common) has direct rent and CAM implications.
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