Stop Treating Every Feasibility Assumption as a Fact

A feasibility can look precise while resting on guesses. A planning yield copied from a sales brochure, a service cost borrowed from another site and a build rate from last year may all sit in identical spreadsheet cells.

A capable developer separates what is known, what is indicated and what is merely assumed. That changes where you spend due-diligence time and how much confidence you place in the result.

Use an evidence ladder

Australian Government risk guidance recommends identifying risks, assessing likelihood and consequence, assigning responsibility and reviewing controls. Planning guidance also makes clear that site characteristics and controls shape development potential. Apply those principles to every material input.

1. Claim: write the assumption in a testable sentence.
2. Class: mark it untested, desktop-indicated, specialist-advised, quoted or contractually confirmed.
3. Consequence: calculate what changes if it is wrong.
4. Conversion: name the evidence needed, its owner and due date.
5. Currency: record when the evidence could expire or require reconfirmation.

A clearly labelled hypothetical

A four-dwelling concept carries a $70,000 allowance for service upgrades. No authority advice or engineering scope supports it. The team labels it untested and high consequence, models a higher downside amount and commissions the appropriate investigation before an unconditional commitment. The number has not become certain; the decision has become more honest.

Do not reward false precision

Adding decimals does not improve evidence. Keep the source beside each input and preserve ranges where outcomes remain uncertain. Ask planners, engineers, builders, brokers, accountants and solicitors to verify matters within their expertise.

The Think Property Club System turns assumptions into visible investigation tasks. Specialists convert the most important unknowns into usable evidence, while Support helps challenge comfortable numbers.

Your next action

Highlight the ten inputs with the greatest effect on your current feasibility. Give each an evidence class, owner, next check and expiry date.

Key Takeaway

A professional feasibility is not the one with the most numbers; it is the one that shows which numbers deserve belief.

Your Turn

Which assumption are you currently treating as a fact, and what evidence would move it one rung higher?

Continue learning

• Development decision log
• Deal-kill criteria

Sources and boundaries

1. Australian Government, Make a risk management plan (current page; accessed 7 September 2026)
2. NSW Planning, Stage 1 – Pre-lodgement (current page; accessed 7 September 2026)

This article is general education, not personalised planning, legal, financial, tax or building advice. Requirements and outcomes vary by jurisdiction, site, contract, structure and circumstances. Check current information with the relevant authority and appropriately qualified advisers.