A development site can look compelling on paper: a favourable purchase price, strong local sales and a planning pathway that appears achievable. Yet knowing how to assess development feasibility means testing whether those assumptions still hold once costs, time, funding and risk are applied. A profitable concept is not the same as a financeable project.
For Australian developers, feasibility is the discipline of turning a proposed project into measurable numbers, then pressure-testing those numbers before contracts are exchanged. It should guide the purchase decision, the funding structure and the point at which a project is adjusted, delayed or walked away from.
Start with the development concept, not the spreadsheet
Every feasibility begins with a clear statement of what is being built and why the site supports it. This includes the proposed dwelling mix, number of lots or units, expected size, target buyer or tenant, construction method and intended exit. A townhouse development aimed at downsizers will have different design, pricing, funding and marketing assumptions from a small apartment project targeting investors.
The site must support the concept physically and legally. Review zoning, overlays, minimum lot sizes, height limits, setbacks, heritage controls, flood or bushfire exposure, access, parking requirements and services availability. A council planning scheme may permit a use in principle while imposing conditions that reduce yield or increase build costs materially.
Early town planning and design input can save significant time. The question is not simply whether a development application may be approved. It is whether the likely approved outcome produces enough value to justify the capital and risk involved.
Build the feasibility from reliable inputs
A useful feasibility separates revenue, development costs, finance costs and contingency. Avoid broad allowances where firmer evidence is available. Small omissions across several categories can turn an apparent margin into a loss.
On the revenue side, estimate gross realisation value using comparable settled sales rather than asking prices alone. Consider location, aspect, floor area, car parking, inclusions, buyer demand and the likely completion date. In a softer market, allow for incentives, longer selling periods and price movement rather than assuming today’s best result will still apply at settlement.
Your cost plan should account for more than the land and builder’s contract. Depending on the project, it may include:
- acquisition costs, including stamp duty, legal fees and due diligence
- demolition, remediation, civil works, connections and authority charges
- consultant fees for planning, architecture, engineering, surveying, certification and project management
- construction, landscaping, driveways, external works and upgrades required by council or service providers
- marketing, sales commissions, holding costs, GST, insurance and contingency.
Finance costs deserve close attention because they move with both time and lender conditions. Include establishment fees, valuation costs, legal fees, interest, line fees where applicable, quantity surveyor reporting and the interest incurred during the construction period. If the project runs six months late, the cost is rarely limited to extra interest. Delayed sales, contractor claims and an extended exposure to market conditions may also affect the result.
Calculate margin, profit and residual land value
The core calculation is straightforward:
Projected gross realisation value - total development cost = development profit.
Total development cost includes the purchase price of the site, all soft and hard costs, finance, taxes and selling expenses. From there, calculate profit as a percentage of total development cost and as a percentage of gross realisation value. Both measures are useful, but neither should be considered in isolation.
A project with a 20 per cent forecast margin may still be unsuitable if the estimate relies on aggressive sales rates, minimal contingency or a long approval period. Conversely, a lower-margin project with exceptional pre-sales, strong equity and conservative assumptions may be more fundable. Lender appetite, borrower experience and the quality of the exit strategy all influence the practical outcome.
Residual land value is particularly useful before you buy. It works backwards from the expected project revenue, deducting all costs and the developer’s required profit to identify the maximum supportable site price. This approach helps avoid a common mistake: paying for a site based on its potential before allowing for the cost and risk of realising that potential.
Test the assumptions that can hurt most
A feasibility should not be a single optimistic forecast. It should include sensitivity testing that shows what happens if the project encounters normal commercial pressure.
Test lower sales values, higher construction costs, additional interest, slower settlements and approval or construction delays. For example, assess the effect of a 5 per cent reduction in gross realisation value, a 10 per cent rise in build costs and a six-month programme extension. The purpose is not to predict the worst possible scenario. It is to understand whether the project has enough margin to absorb realistic variation.
Contingency is separate from sensitivity testing. A contingency allowance is included in the base budget to cover foreseeable unknowns, while sensitivity testing asks what happens when key assumptions change beyond the base case. The right contingency depends on design maturity, ground conditions, procurement method and project complexity. A straightforward, fully documented build may warrant a different allowance from a site with demolition, retaining walls or uncertain service connections.
Assess funding feasibility alongside project feasibility
A commercially sound project still needs an achievable lending structure. Development lenders will generally examine the borrower’s experience, equity contribution, project team, valuation, total development cost, loan-to-cost ratio, loan-to-value ratio, contingency, presales and exit strategy.
The lender’s valuation can be decisive. If it comes in below your assumed end values or land value, the available debt may reduce and increase the equity required. Similarly, construction funding is usually drawn progressively against completed works, so cash flow must cover early costs and any gap between invoices and lender drawdowns.
Consider whether the project is intended to be sold down, refinanced on completion or held as an investment. A sell-down strategy needs realistic buyer demand and settlement timing. A refinance strategy needs sufficient completed value, rental income and serviceability. If the exit depends on one highly favourable outcome, it needs more scrutiny.
Specialist advice early in the process can clarify whether a proposed structure is likely to meet lender requirements before significant deposits and consultant costs are committed. The Finance Office can help developers consider funding options alongside the project’s broader feasibility, rather than treating finance as an afterthought.
Use a staged decision process
The best feasibility work is updated as better information becomes available. Before making an offer, use high-level estimates to establish a maximum price and identify major planning or site risks. During due diligence, replace assumptions with planning advice, preliminary design, comparable sales evidence, builder input and a clearer funding indication.
Once the development application and detailed design progress, revise the feasibility again. Construction quotes, conditions of consent, service authority requirements and updated valuations can change the economics. Treat the spreadsheet as a live decision tool, not a document prepared once to justify a purchase.
It can also be wise to set clear walk-away points. If approval reduces yield, tender pricing exceeds the budget or the valuation weakens, the right response may be to redesign, renegotiate or not proceed. Discipline at this stage protects capital for the next opportunity.
Common feasibility errors to avoid
Many development feasibility problems begin with overconfidence in one area. Some developers use optimistic asking prices as evidence of end value. Others rely on a broad construction rate that does not reflect retaining, basements, access constraints, joinery, external works or site-specific conditions.
Tax is another area that should be modelled properly. GST treatment, including whether the margin scheme may apply, can materially affect projected profit. Development profits may also have income tax implications that differ from a long-term investment. Obtain advice from an accountant or tax adviser who understands property development before relying on a headline profit figure.
Finally, do not assume time is neutral. Council assessment periods, appeals, weather, material lead times, contractor availability and settlement delays each have a cost. A project that looks attractive over 18 months may look very different over 30 months.
A strong feasibility does not promise certainty. It gives you a disciplined basis for deciding what to pay, how much equity to commit and where the project needs more investigation. Before you commit to a site, make sure the numbers can withstand more than the best-case scenario.
