Testing buildability early (site access, excavation, structure, services and procurement) turns unknowns into priced risks before you agree a land price or lock in a design. It rarely changes whether a site is good. It often changes what the site is worth to you.

What a development feasibility actually tests

A residential development feasibility answers one question: after every cost, does the project leave enough margin for the risk you are taking? It weighs the expected end value of the finished homes (the gross realisation) against land, construction, professional fees, approval costs, finance, holding costs, selling costs and taxes. Run in reverse, the same model tells you the most you can pay for the land and still hit your target margin, which is the residual land value.

The end values usually get the most attention, because they are visible in comparable sales. The construction cost is often a single rate per square metre. That rate is where buildability problems hide. A feasibility built on an average rate assumes an average site. Sydney sites are rarely average.

Where buildability hides in the numbers

These are the items that most often move a residential feasibility in Sydney, and they can usually be investigated cheaply before purchase or design:

  • Site access and logistics. Narrow frontages, steep driveways, battle-axe lots and busy roads limit machinery, deliveries and crane options. Restricted access slows every trade and adds traffic management.
  • Excavation, rock and basements. Sandstone is common across much of Sydney. Rock breaking, spoil removal, dewatering and shoring can make a basement far more expensive than its floor area suggests.
  • Retaining and neighbours. Excavation near boundaries means retaining walls, possible underpinning and dilapidation surveys of neighbouring properties before work starts.
  • Structure. Long spans, cantilevers, large openings and transfer structures add steel and engineering cost. They are design choices worth making deliberately, not by default.
  • Services and stormwater. Sewer location, stormwater discharge, on-site detention, power supply capacity and water connection can each require design changes or authority works.
  • Trees, heritage and environmental constraints. Protected trees, heritage items, flood or bushfire affectation shape the footprint and sometimes the approval pathway itself.
  • Procurement lead times. Windows, façade systems, stone and joinery can have long lead times. If they are not planned with the programme, the site waits, and holding costs accrue.

The cost of finding out late

Each of these items costs something whenever it is discovered. The difference is what can still be done about it. Found during due diligence, an issue can be priced into the land offer, designed around, or used to walk away. Found after the design is approved, it usually means a redesign, a modification application or a variation. Found during construction, it means delay, and on a funded project delay compounds through interest and holding costs.

An illustration, not a forecast. Imagine two duplex sites with the same land price and the same expected end values. One is level with good access. The other slopes to a rear boundary, has rock near the surface and drains away from the street. A feasibility using the same construction rate for both will show the same margin. A buildability review will not, and that difference belongs in the land price rather than in the builder's variations.

The point is not that difficult sites are bad. Many of the best sites in Sydney are sloping, rocky or constrained, and the constraint is often what keeps the land price reasonable. The point is to price it.

What a practical early buildability review looks like

An early review does not need a full design. It needs the right questions asked of the right information:

  1. Collect the basics: survey (or at least a contour plan), the NSW Section 10.7 planning certificate, sewer and stormwater diagrams, and any geotechnical information available.
  2. Confirm the likely approval pathway, CDC or DA, because it constrains the design envelope and the programme.
  3. Sketch a realistic massing that fits the planning controls, including excavation depth and driveway grades.
  4. Ask a builder or estimator to identify the cost drivers of that massing on that site, not a generic rate.
  5. Check services capacity and connection points with the relevant authority information.
  6. List long-lead procurement items and when they would need to be ordered.
  7. Run the feasibility again with the adjusted costs, programme and a contingency that reflects what is still unknown.

This can usually be done in days, not months, and for a small fraction of the cost of a design that later has to change.

Who should be involved

Buildability is not a separate consultant's job. It sits between disciplines. The designer understands what the planning controls allow; the builder knows what the site will cost to build on; the finance side knows how delay and cost movement affect funding; and the sales side knows which compromises buyers will accept. A feasibility is strongest when those views meet early.

This is the reason AUD Group coordinates development strategy, architecture and design, construction input, procurement and finance coordination around one set of project information, while each business keeps its own scope and responsibilities.

Checklist: before you commit to a site or a design

  • Is the construction cost based on this site, or on an average rate?
  • Do you know the excavation depth, likely rock and retaining needs?
  • Have access, deliveries and crane options been considered?
  • Are sewer, stormwater, detention and power capacity confirmed?
  • Is the approval pathway clear, and does the programme reflect it?
  • Are long-lead items identified and timed?
  • Does the margin survive a slower sale, a cost increase and a three-month delay?

If several answers are "not yet", the feasibility is still an estimate of a project you have not fully seen.

This article is general information, not financial, legal, planning or construction advice. Project costs, approvals and outcomes depend on the specific site and must be assessed by appropriately qualified professionals.