Published 20 October 2026 · 7 minute read
Most residential deals are won or lost on one early question: how much can we build here, and what is it worth? Answering it used to mean days of sketching, area schedules and spreadsheet work before anyone knew if the site was worth pursuing. With a generative tool you can get a defensible first answer in about ten minutes, then spend your design time on the sites that deserve it.
1. Gather the controls before you draw
The answer is only as good as the rules you feed in. Before opening any tool, collect:
- From the local environmental plan: maximum building height (metres), floor space ratio (FSR) and the zone (which tells you whether ground-floor retail is required or allowed).
- From the development control plan: front, side and rear setbacks, site coverage or landscaped area, car parking rates by apartment size, and any street-wall or podium rules.
- From the apartment design rules in your state: in NSW that is the Apartment Design Guide, which sets minimum apartment sizes (35, 50, 70 and 90 m² for studio to 3-bed with one bathroom), building separation (12, 18 and 24 m as buildings get taller), solar access, cross-ventilation, deep soil and communal open space targets.
- Your market: the unit mix buyers want, achievable sale prices per square metre and a rough land price.
If the height and FSR controls are inconsistent (for example an FSR you could only reach with 12 storeys on a site limited to 8), the generator will show you which control actually binds. That alone is often the most valuable early insight.
2. Set up the site
Search the address in the designer to import surrounding buildings, roads and trees, then add terrain if the site slopes. Draw the boundary, pick the lot from the map, or import the survey as a DXF. Set the setback for each edge and mark the street frontage (where the car-park ramp will go). The dashed red outline is your buildable envelope.
3. Generate, then compare honestly
Choose the typologies that suit the site and the market. Linear bars and L-shapes suit narrow lots, courtyards and U-shapes suit large regular sites, and towers suit high FSR on small footprints. Pick an objective and generate. You will get a ranked set of options, each with a complete floor plan, basement and feasibility.
Do not just take the highest yield. Compare at least three options on:
- Net sellable area and efficiency: how much of the gross building area you can actually sell. Double-loaded mid-rise schemes usually land around 70 to 80 percent.
- Midwinter sun and cross-ventilation: amenity failures are where planning approvals stall, and they are expensive to fix later.
- Basement levels: parking demand, not floor area, often decides cost. A second basement level can wipe out the profit from an extra storey.
- Profit and residual land value: the residual tells you what you can afford to pay for the land at your target margin.
4. Refine the preferred option
Move or rotate a building to open a view or a courtyard, change storeys to step the height down to a neighbour, or swap a typology. Every change updates the unit program, compliance and feasibility immediately, so you see the cost of each design decision as you make it.
5. Stress-test the numbers
Replace the indicative construction rates with your quantity surveyor's, then use the sensitivity grid: if a 5 percent fall in prices and a 5 percent rise in costs turns the profit negative, the site needs a better price or a different scheme.
Common traps in early feasibility
- Confusing GFA with saleable area. Planning controls cap gross floor area; buyers pay for net sellable area. Read FSR, GFA, GBA and NSA explained.
- Forgetting parking. At typical rates a 150-unit scheme needs well over 100 spaces. See basement car park layout basics.
- Ignoring separation. Two buildings at 8 storeys need 18 m between them under the ADG, which can make two small buildings worse than one larger one.
- Treating a first pass as a design. Generated options are for decisions about whether and how to proceed. Engage an architect and planner before committing.
Next step
Run your next site through the designer, export the Excel report and take it to your first meeting with the consultants. If you want the tool to use your own apartment plans, rates or feasibility model, we build custom versions.