Methodology
How the Airspace Calculator works.
No black box. These are the exact factors and benchmarks behind every number the calculator shows you.
1. Usable airspace
Gross roof area is multiplied by a structural and setback efficiency factor. Strata residential roofs carry plant, lift overruns, access and boundary setbacks, so we allow 42% usable. Commercial roofs are typically cleaner and more regular at 52%.
2. Module capacity
Usable area is divided by a typical module footprint — 55 m² per residential pod including circulation and deck allowance, 50 m² per commercial pod — and rounded down to whole modules. Every roof yields at least one module in the model.
3. Rental yield
New floor area is valued at the city rental benchmark per square metre per annum, then discounted to 92% to allow for vacancy and letting costs. The figure is gross — it excludes strata levies, management fees, insurance and tax.
4. Capital value
New floor area is valued at the city sale benchmark per square metre for recently completed premium small-footprint stock. It is a completion value, not a valuation, and excludes construction cost, professional fees and GST.
Benchmarks by city
| City | Rent benchmark | Sale benchmark |
|---|---|---|
| Sydney, NSW | $1,180 / m² p.a. | $15,200 / m² |
| Melbourne, VIC | $890 / m² p.a. | $11,400 / m² |
| Brisbane, QLD | $830 / m² p.a. | $10,600 / m² |
Efficiency factors
- Strata Residential42% usable · 55 m² per module
- Commercial52% usable · 50 m² per module
Benchmarks are reviewed quarterly against published rental and settled-sale data for each market. The calculator is a screening tool: it tells you whether a building is worth investigating, not what it is worth. A funded structural feasibility scan is the first real number in any project.
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