The same building can have different design, internal, usable, leasable and billable areas. The measurement boundary, standard and purpose determine the result.
COMPARE TERMS ↓A client, landlord, lender and designer may each use a different area metric — and each figure can be correct for a different purpose. The problem starts when figures are compared without a common methodology.
The table shows typical use. The exact scope of every metric must be verified against the relevant method and records.
| Term | Basic boundary | Typical use | What to verify |
|---|---|---|---|
| GEA | External perimeter | Whole-building analysis, insurance, benchmarking | Balconies, canopies, atria and open areas |
| GIA | Internal face of enclosure | Cost, technical analysis, industrial property | Shafts, atria and internal construction |
| NIA | Net functionally usable interior | Occupation, capacity and space comparison | Excluded circulation, plant and common areas |
| GLA / NLA | Contractually defined leasable area | Rent, income and occupancy | Lease definition and adopted standard |
| GFA / BUA | Design or local definition | Design, development and planning | Project terminology and local rules |
For every term we distinguish the physical boundary, commercial purpose and risk of misuse.
GEA describes building area measured to the outside of the external enclosure. It is useful when the complete built envelope, including perimeter construction, matters rather than only internal space.
GIA is measured to the internal face of the external enclosure. It captures gross internal capacity, generally before deductions for internal walls, columns, circulation and plant areas under the adopted method.
NIA represents internal area available for functional occupation after exclusions required by the adopted standard. It may be more useful for capacity and operating decisions than a gross figure.
GFA and BUA often appear in design, development and planning records. Their meaning is not globally uniform: GFA may denote aggregate floor area while BUA may describe a footprint or a broader built area.
GLA and NLA are used in leasing, investment modelling and occupancy reporting. In practice they are not safely interchangeable universal figures. Lease definitions, the measurement standard and common-area allocation govern.
Billable area is the contractual base for rent or charge calculations. It may comprise exclusively occupied space, an allocated share of common areas and other contractually agreed areas.
An add-on factor allocates a share of common areas to exclusive space. It may be calculated at floor level, building level or in several stages depending on the lease and standard.
Usable area describes space practically available for its intended function. It may be defined by law, design documents, a standard or a client's internal rules, so it should not be equated with NIA or NLA without verification.
BOMA is not one fixed formula but a suite of measurement standards for different commercial property types. The result depends on asset class, standard edition, selected method and common-area allocation rules.
IPMS provides a common international measurement framework across building types and markets. It uses distinct terminology to reduce ambiguity in historic local terms and can be reported alongside a local method.
The objective is not to declare one metric universally correct, but to show exactly what each figure means and where differences arise.
Lease, finance, CAPEX, building passport, capacity or design decision.
Leases, rent roll, drawings, BIM, cadastral and approval records.
Identify the standard, edition, boundaries, exceptions and allocation rules.
Targeted measurement or 3D scan for discrepancies not explained by records.
Difference schedule, method, risk and recommendation for the decision or contract.
For international and portfolio assignments we follow the standard specified by the client or contract and verify its current edition. These links are orientation only; the specific document and edition govern.
IPMS Coalition — International Property Measurement Standards ↗BOMA International — Floor Measurement Standards ↗
We define the method, review the records and explain differences for use in contracts, financing and asset management.
info@audico.sk ↗