---
title: "How We Calculate | KnockdownRebuildCost Methodology"
description: "Our KDR calculator models 20+ cost factors including demolition, site prep, build quality, holding costs, and hidden expenses."
source: KnockdownRebuildCost
sourceUrl: https://kdrcost.com/how-we-calculate
lastUpdated: 2026-05-31
citationUrl: https://kdrcost.com/how-we-calculate
---

# How We Calculate

Our KDR calculator models 20+ cost factors including demolition, site prep, build quality, holding costs, and hidden expenses.

The core of any KDR estimate is the new build cost. We calculate this using per-square-metre rates that vary by quality tier:

Not all blocks are created equal. Our model adjusts costs based on two key site conditions:

This is where most online calculators fall short. During a knockdown rebuild, you cannot live in the property. A typical KDR project takes 10 to 14 months from demolition to handover. During that time, you need somewhere to live and somewhere to store your belongings. We estimate:

Beyond the headline numbers, knockdown rebuilds involve a long tail of smaller costs that add up. Our calculator includes estimates for:

All cost data is sourced from publicly available information including ABS construction cost indices, builder pricing guides, government fee schedules, and community-reported costs. For the full list, see our data sources page.

## City-Specific Cost Multipliers

## Demolition Cost Modelling

## Build Cost Per Square Metre

## Site Condition Adjustments

## Council and Approval Costs

## Holding Costs

## Hidden and Commonly Missed Costs

## Renovation Comparison

## Where Our Data Comes From

#### Guides

#### Company

## Key Points

- Standard: Basic fixtures, standard materials, minimal customisation. Suitable for investment properties or budget-conscious builds.
- Mid-range: Better fixtures, some custom joinery, engineered stone benchtops, quality flooring. The most common choice for owner-occupiers.
- Premium: High-end fixtures, custom cabinetry, premium appliances, designer finishes throughout. Architect-designed homes typically fall here.
- Luxury: Top-tier everything — imported materials, bespoke design, premium automation, and high-end landscaping. Custom architectural homes with no compromises.
- Slope: Flat blocks are cheapest to build on. Gentle slopes add costs for cut-and-fill or split-level design. Steep blocks require significant earthworks, retaining walls, and potentially piered foundations — adding tens of thousands to the build.
- Temporary rent: Based on median rental prices in your city for a comparable dwelling, multiplied by the expected build duration.
- Storage: Monthly self-storage unit costs for a standard household, multiplied by build duration.
- Temporary fencing: Required during demolition and construction to secure the site.
- Soil testing and site survey: A geotechnical report and contour survey are typically required before design can begin.
- Driveway and crossover: The existing driveway is destroyed during demolition. A new driveway and potentially a new council crossover must be built.

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*Source: [KnockdownRebuildCost](https://kdrcost.com/how-we-calculate)*