---
title: "Data Sources & Research Methodology | DuplexCost"
description: "Examine the real-world Australian data sources, council contribution schedules, and volume builder catalogs that inform the DuplexCost calculator engine."
source: DuplexCost
sourceUrl: https://duplexcost.com/data-sources/
lastUpdated: 2026-07-01
citationUrl: https://duplexcost.com/data-sources/
---

# Data Sources & Methodology

Examine the real-world Australian data sources, council contribution schedules, and volume builder catalogs that inform the DuplexCost calculator engine.

How our mathematical engine calculates duplex feasibility and turnkey building costs.

We actively monitor base package pricing and structural options from major Australian volume and boutique duplex builders, including:

Zoning and compliance constraints are verified against authoritative planning documents:

Developer contributions (required by local councils to offset increased density loads) are integrated into our soft-costs calculations:

Weekly rent and yield metrics are calculated utilizing city-level median data Sourced from the ABS Housing Census, Domain and REA Rental Reports, and median suburban transaction indexes, modeling Sydney median rents at $950/week per side and Melbourne at $720/week.

## 1. Volume Builder Catalogues & Turnkey Markups

## 2. State and Local Council Planning Instruments

## 3. Developer Contributions & Infrastructure Levies

## 4. Rental Indexes & Property Valuations

#### Guides

#### Company

## Key Points

- Metricon Homes (DualOcc Range): Ritz, Bordeaux, and La Pyrenees specifications, setting our baseline double-storey attached $Rate/sqm of $2,200 – $2,500.
- Rawson Homes (Duplex Solutions): Chifley and Balmoral catalogues, validating our 12% detached building premium.
- New South Wales: Under the State Environmental Planning Policy (SEPP - Low Rise Housing Diversity Code), validating our minimum 580 sqm lot size and 15m frontage requirements for Complying Development (CDC).
- Victoria: ResCode schedules (Clause 55), validating Neighbourhood Residential Zone (NRZ) minimum lot sizes (600–700 sqm) and Monash/Glen Eira garden permeability/canopy tree rules.
- Queensland: Brisbane City Plan 2014, defining Low-Medium Density Residential (LMR) code assessable pathways.
- Sydney Councils (Section 7.11/7.12): Sourced from Canterbury-Bankstown, Ryde, Parramatta, and Penrith developer contribution schedules, averaging $25,000 per additional lot.
- Melbourne Councils (DCP / municipal levies): Sourced from Monash and Whitehorse DCP plans, averaging $18,000 per dwelling.
- Cost to Build a Duplex
- CDC Duplex Requirements
- Best Sydney Builders

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*Source: [DuplexCost](https://duplexcost.com/data-sources/)*