How Much Does a Home Extension Cost?

Planning a home extension in Melbourne requires careful financial preparation. Home extension cost varies significantly based on your specific requirements and chosen materials.

At Cameron Construction, we’ve helped hundreds of Melbourne families navigate extension budgeting. Understanding the true costs upfront prevents budget blowouts and project delays.

What Drives Your Extension Costs

Extension costs depend on four primary factors that Melbourne homeowners often underestimate. The size and complexity of your extension represents the largest cost driver, with ground floor additions typically ranging from $2,500 to $4,000 per square metre, while double storey extensions cost between $3,500 to $5,500 per square metre according to recent industry data. Complex designs with multiple roof lines, custom structural elements, or integration challenges with existing heritage features can increase costs compared to straightforward rectangular additions.

Material Selection Impact on Budget

Your material and finish choices directly affect the final price tag. Standard brick veneer construction with basic fixtures costs approximately 40 per cent less than premium materials like natural stone cladding or engineered timber. Kitchen and bathroom fitouts represent significant cost centres, with premium appliances and custom joinery adding $15,000 to $40,000 to your budget. Flooring choices alone can vary from $80 per square metre for quality hybrid flooring to $300 per square metre for solid hardwood or natural stone tiles.

Site Conditions Shape Construction Costs

Melbourne’s diverse topography creates varying site challenges that impact pricing. Sloping blocks require additional excavation, retaining walls, and structural engineering (potentially adding $20,000 to $60,000 to your project cost). Properties with poor soil conditions need specialised footings, while sites with limited access for machinery increase labour costs by 15 to 25 per cent. Underground services, mature trees that require protection, or heritage overlays all contribute to higher construction expenses that standard quotes may not capture initially.

Planning Permits and Council Requirements

Council requirements add both time and cost to your extension project. Planning permits for home extensions typically cost between $1,500 and $3,000 (depending on project complexity and local council fees). Building permits range from $200 to $1,500 based on the scope of work.

Properties in heritage overlays face additional approval processes that can extend timelines by 6 to 12 weeks and increase professional fees by $5,000 to $15,000. Each council has specific requirements for setbacks, height limits, and design guidelines that influence your extension’s final design and cost structure.

These cost factors work together to determine your total investment, but understanding the specific pricing for different extension types helps you plan more accurately.

What Does Each Extension Type Really Cost

Ground floor extensions provide the most cost-effective space expansion for Melbourne families, with construction costs that range from $2,500 to $4,000 per square metre according to Australian Bureau of Statistics construction price index data. These single-level additions work particularly well on level blocks where foundation requirements remain straightforward. A typical 40-square-metre ground floor extension that includes kitchen and areas costs between $100,000 and $160,000 for quality construction with mid-range finishes. The price advantage comes from simpler structural requirements, direct access for trades, and reduced scaffolding costs compared to multi-level projects.

Double Storey Extensions Command Premium Pricing

Double storey extensions cost significantly more at $3,500 to $5,500 per square metre, which reflects complex structural requirements and increased labour demands. The Building and Plumbing Commission data shows these projects require specialised foundation systems, steel frames, and comprehensive waterproofing that adds 40 to 60 per cent to construction costs. A 60-square-metre double storey extension typically ranges from $210,000 to $330,000 (including structural work and quality finishes). The investment delivers maximum space gain on smaller blocks while it maintains valuable outdoor areas that ground floor extensions would consume.

Second Storey Conversions Present Unique Challenges

Converting existing roof space into liveable areas costs between $2,800 and $4,200 per square metre, with pricing that existing structural capacity heavily influences. Properties built before 1990 often require complete roof reconstruction and structural upgrades, which pushes costs toward the higher range.

Staircase installation alone adds $15,000 to $25,000 to your budget, while dormer windows or roof modifications can increase costs by another $20,000 to $40,000. These conversions work best on homes with adequate ceiling height and strong existing foundations that can support additional loads without major structural intervention.

Understanding these extension costs helps you choose the right approach, but several hidden expenses can catch homeowners off guard during the construction process.

What Hidden Costs Should You Budget For

Extension projects in Melbourne consistently exceed initial budgets by 15 to 30 per cent due to hidden costs that homeowners overlook during early planning stages. Council fees extend far beyond basic permit applications, with development contribution levies adding $2,000 to $8,000 for larger extensions depending on your suburb. Building permit levies cost 0.128 per cent of construction value for projects exceeding $10,000, while private building surveyor fees range from $3,000 to $8,000 for comprehensive inspections.

Heritage overlay properties face additional consultant fees of $5,000 to $12,000 for specialist reports and extended approval processes that can stretch project timelines by three months. These costs compound quickly when multiple approvals are required.

Council Fees and Development Contributions

Development contribution levies vary significantly across Melbourne councils, with some charging up to $8,000 for substantial extensions. The Building and Plumbing Commission imposes permit levies on all projects exceeding $10,000 in value. Private building surveyors charge between $3,000 and $8,000 for inspection services throughout your project.

Planning permit applications cost $1,500 to $3,000 depending on complexity, while building permits range from $200 to $1,500. Properties in heritage overlays require additional specialist reports that add $5,000 to $12,000 to your budget.

Utility Infrastructure Upgrades Drive Unexpected Expenses

Existing electrical panels in Melbourne homes built before 2000 often require complete upgrades to handle extension loads, costing $3,000 to $6,000 according to Electrical Safety Victoria guidelines. Gas meter relocations add $1,500 to $3,000 when extensions interfere with existing connections. Water main upgrades for additional bathrooms cost $2,000 to $5,000.

Stormwater management represents a significant hidden expense, with new drainage systems and retention tanks adding $8,000 to $15,000 to comply with Melbourne Water requirements. Sewer connection modifications for additional toilets or kitchens cost between $3,000 and $8,000 (particularly on older properties with clay pipes that require complete replacement).

Temporary Accommodation and Project Delays

Kitchen and bathroom extensions force families into temporary accommodation or expensive alternative arrangements during construction phases. Rental accommodation for 3 to 6 months costs $15,000 to $35,000 in Melbourne’s current market, while extended hotel stays during critical construction phases add $200 to $400 per night.

Weather delays during winter months extend projects by 2 to 4 weeks, increasing labour costs by $8,000 to $15,000. Soil conditions, structural discoveries, and council requirement changes consistently impact final costs beyond initial estimates. Budget 20 per cent contingency for extension projects to cover these unexpected expenses.

Final Thoughts

Home extension cost varies significantly based on multiple factors that affect your final investment. Ground floor extensions start at $2,500 per square metre, while double storey additions range from $3,500 to $5,500 per square metre. Hidden expenses consistently add 15 to 30 per cent to initial budgets through council fees, utility upgrades, and temporary accommodation costs.

Accurate budgets demand detailed quotes from registered builders, comprehensive site assessments, and realistic contingency plans. Factor in permit costs, structural requirements, and material selections early in your process. Weather delays, soil conditions, and council requirement changes represent common budget challenges that proper preparation can mitigate.

We at Cameron Construction have guided Melbourne families through extension projects for decades. Our approach includes detailed cost analysis, permit management, and transparent pricing that eliminates budget surprises. Contact our team for a comprehensive assessment of your extension requirements and accurate cost projections tailored to your specific property and goals.