Detailed cost estimates come late in the design process at the end of design development, or at tender. By that point, the decisions that drive most of the cost have already been made. Changing structural span, floor count, or envelope area at tender stage is enormously expensive. Getting rough but honest cost data at the concept stage changes the conversation before it matters.
Why Early Cost Numbers Are Hard to Trust
The reason detailed cost estimating happens late is that it requires detail. A proper QS estimate needs drawings. But 'we'll cost it properly later' creates a pattern where schemes get developed in full detail, costed, fail the budget, and then require expensive redesign. The alternative is parametric cost modeling rough but directionally correct estimates from massing alone.
What Brox's Cost Model Covers
- Structural system cost per sqm varies by floor count, span, and structural type
- Envelope area and glazing ratio key cost multipliers set by massing decisions
- MEP complexity estimated from floor count, program type, and core configuration
- Fit-out grade client-specified, from standard to premium, applied to finish-sensitive line items
- External works and services estimated from lot coverage and program
The Decision That Costs the Most
The single most expensive concept-stage decision is floor count. Adding a floor increases structure, vertical circulation, and MEP distribution proportionally. It also resets planning requirements a building that crosses a height threshold may trigger different structural, fire, and accessibility requirements that cost more per square metre than the additional floor. Brox surfaces this trade-off at the scoring stage.
Budget Ceiling as a Design Constraint
When you enter a hard budget ceiling in your Brox brief, the cost model runs against it for every massing option. Options that exceed the budget are not presented as viable alternatives they are flagged as over-budget with the percentage gap stated. This means you receive concepts that are genuinely within budget, not concepts that are 'within budget pending value engineering.'
Tip
Use Brox's cost model as a filter, not a quote. The parametric estimates are useful for ruling out options that are clearly too expensive and ranking options by cost-efficiency. Get a real QS estimate for the concept you choose before committing to detailed design.
Run a Cost-Modeled Brief
Enter your lot, program, and budget Brox scores every concept against your cost ceiling before you see it.
Start a Brief →
