Back to Airspace Connect

The airspace assessment rule

One rule, one answer — the same calculation Buy Airspace uses. The map's "1+ storeys" filter counts every assessed building where at least one 3.1 m level fits under the height limit and the floor space ratio (when known) isn't used up.

Height per level
3.1 m
Rate
$2,500–$6,500/m²
Floor space per home
75 m²

The steps, in order

1. Measure from the gutter lineSpare height is measured from the eave (gutter line) where it is recorded, otherwise from the top of the roof. The measured height is never rounded up.
2. Spare heightCouncil height limit minus the measured height. A building already at or above the limit has no spare height — never a negative number.
3. Levels that fit (3.1 m each)Spare height divided by 3.1 m per level, rounded down.
4. Floor space checkNew floor space is the roof footprint times the levels that fit, capped by the floor space ratio: ratio x land area, less the floor space already built. Where no ratio or land area is published, the height limit alone sets the capacity — nothing is assumed.
5. Pitched roofs with no spare heightIf no new level fits but the roof is pitched, the attic space is the whole roof footprint. Half of it is habitable, and that habitable half is what gets valued. A flat roof at or over the limit is worth nothing.
6. One rate: a quarter of the local sale rate, $2,500 to $6,500/m²The rate is 25% of the local new-apartment sale rate per m² for the postcode, held between the base and the cap. Where no local sale rate is known, the base rate applies — never a guess.
7. Homes at 75 m² eachNew floor space divided by 75 m² per home. It takes 150 m² of attic to make one 75 m² home.

Assessment ranges

Everywhere on Airspace Connect — property cards, the map, search filters, alerts and free estimates — an assessment is shown only as one of these ranges. The actual assessment amount appears only in a paid assessment report.

$1 – $500k
$501k – $1m
$1m – $2m
$2m – $3m
$3m – $5m
$5m – $10m
$10m+

Assessment allowance and pricing

Pro members ($49/month)Three assessments included free each calendar month (Sydney time). The allowance resets on the 1st and unused assessments don't carry over.
After the three free assessmentsEach further assessment that month is $49 (incl. GST).
Without ProA single assessment report is $49 (incl. GST).

Worked examples, calculated live

12 Ramsgate Avenue, Bondi Beach

$137,500
Extra levels: 1
New floor space: 55 m²
Attic space: 0 m²
Homes: 1
  1. Existing building: 441 m² of floor space over 2 level(s), roof footprint 221 m², pitched roof.
  2. Height measured from the gutter line (eave): 9.38 m.
  3. Height limit used: 12.5 m (council limit).
  4. Spare height: 12.5 m limit − 9.38 m measured = 3.12 m.
  5. Extra levels that fit: 1.01 rounded down at 3.1 m per level = 1.
  6. New floor space from those levels: 221 m² × 1 = 221 m².
  7. Floor space allowed by the floor space ratio: 0.9 × 551 m² of land = 496 m², less 441 m² already built = 55 m² spare.
  8. We take the smaller of the two: 55 m².
  9. Rate: $2,500/m² — the base rate, as no local new-apartment sale rate is known.
  10. Value: 55 m² × $2,500/m² = $137,500.
  11. Homes: 55 m² ÷ 75 m² per home = 1.

1 Hastings Parade, Bondi Beach

$202,500
Extra levels: 0
New floor space: 0 m²
Attic space: 161 m²
Homes: 1
  1. Existing building: 644 m² of floor space over 4 level(s), roof footprint 161 m², pitched roof.
  2. Height measured from the gutter line (eave): 11.84 m.
  3. Height limit used: 12.5 m (council limit).
  4. Spare height: 12.5 m limit − 11.84 m measured = 0.66 m.
  5. Extra levels that fit: 0.21 rounded down at 3.1 m per level = 0.
  6. No published floor space ratio or land area, so the height limit alone sets the capacity.
  7. Rate: $2,500/m² — the base rate, as no local new-apartment sale rate is known.
  8. No room for a new level, but the roof is pitched: the attic space is the whole roof footprint — 161 m².
  9. Habitable part of that attic (the roof slopes away): 161 m² × 50% = 81 m².
  10. Value: 81 m² × $2,500/m² = $202,500.
  11. Homes: 81 m² of habitable attic ÷ 75 m² per home = 1 (that is 161 m² of attic ÷ 150 m²).

109 Oxford Street, Bondi Junction

$0
Extra levels: 0
New floor space: 0 m²
Attic space: 0 m²
Homes: 0
  1. Existing building: 9,231 m² of floor space over 17 level(s), roof footprint 543 m², flat roof.
  2. Height measured from the top of the roof (no gutter line recorded): 53.3 m.
  3. Height limit used: 38 m (council limit).
  4. Spare height: none — the building is already at or above the limit.
  5. Extra levels that fit: 0 rounded down at 3.1 m per level = 0.
  6. Floor space allowed by the floor space ratio: 5 × 1,402 m² of land = 7,010 m², less 9,231 m² already built = 0 m² spare.
  7. We take the smaller of the two: 0 m².
  8. Rate: $2,500/m² — the base rate, as no local new-apartment sale rate is known.
  9. No spare height and a flat roof, so no attic to convert — nothing to value, $0.
  10. Homes: 0 m² ÷ 75 m² per home = 0.