Single Storey Extension Cost: Complete Guide

Single storey extension cost planning starts with understanding Melbourne’s current market rates and the factors that drive your final investment.

At Cameron Construction, we’ve guided hundreds of homeowners through extension projects, from compact rear additions to expansive open-plan living spaces.

This guide breaks down real costs, hidden expenses, and smart strategies to maximise your renovation budget.

What Do Single Storey Extensions Actually Cost

Melbourne’s single storey extensions currently range from $2,200 to $3,500 per square metre for quality construction, with most homeowners investing between $2,400 and $2,900 per square metre according to recent industry data. These figures reflect completed projects that include structural work, electrical, plumbing, and standard finishes, but exclude high-end materials or complex site conditions.

Extension Type Costs

Rear extensions with basic kitchen integration cost $2,200 to $2,800 per square metre, while open-plan extensions that incorporate premium kitchens and multiple services reach $2,800 to $3,500 per square metre. Side return extensions typically fall in the middle range at $2,400 to $3,200 per square metre. Wrap-around extensions command premium rates due to increased complexity and structural requirements.

Site Factors That Drive Costs

Site access significantly impacts your budget, with restricted access sites adding 15-25% to base costs due to manual handling and equipment limitations. Foundation requirements vary dramatically across Melbourne’s diverse soil conditions, with reactive clay sites requiring specialised soil treatment and deeper footings that increase project costs.

Permit and Regulatory Expenses

Planning permit fees range from $1,400 to $2,800 depending on council requirements, while building permits add another $2,000 to $4,500. These costs vary significantly between Melbourne councils (with some charging higher fees for complex applications).

Material Specifications Impact

Material specifications create the largest cost variations in any extension project. Engineered stone benchtops, hardwood floors, and premium fixtures can potentially double finish costs compared to standard specifications. The choice between basic and premium materials often represents the difference between a $2,200 and $3,500 per square metre project.

Understanding these cost factors helps you prepare a realistic budget, but several additional elements will influence your final investment amount.

What Drives Your Extension Budget Higher

Melbourne’s extension costs vary dramatically based on three critical factors that builders often underestimate during initial planning. Site conditions create the biggest budget surprises, with sloping blocks adding $15,000 to $35,000 for retaining walls and complex drainage systems. Poor soil conditions require expensive underpinning or pier foundations, particularly in Melbourne’s eastern suburbs where reactive clay soils dominate.

Access restrictions through narrow side passages or heritage streetscapes force manual material handling, which increases labour costs by 20-30% compared to standard access sites.

Material Selection Creates Cost Extremes

Your material choices determine whether you pay $2,200 or $3,500 per square metre for the same extension footprint. Engineered stone benchtops cost $800 per linear metre compared to $300 for laminate, while hardwood floors add $150 per square metre over standard tiles. Premium double-glazed windows increase costs by $2,500 to $4,000 per extension but deliver long-term energy savings. We recommend that you select three key premium materials rather than upgrade everything, with focus on items that add genuine value like kitchen benchtops, floors, and bathroom fixtures.

Council Requirements Vary Significantly

Planning permit costs fluctuate between Melbourne councils, with Boroondara charging $2,800 compared to Casey’s $1,400 for similar extensions according to recent council fee schedules. Building permit fees depend on construction value and typically range from $2,000 to $4,500 for standard single storey additions. Some councils require additional reports like heritage assessments or traffic impact studies, which add $3,000 to $8,000 to your project timeline and budget. By law, builders or tradespeople must take out domestic building insurance for their clients when the cost of the works exceeds $16,000, affecting contract structures and builder selection processes.

These cost variables highlight why accurate budgets require professional assessment, but smart design strategies can help you maximise value from your investment regardless of site challenges.

How Much Value Do Extensions Actually Add

Melbourne extensions deliver strong returns when homeowners plan strategically, with rear extensions adding substantial value to property values according to recent housing data. Kitchen-focused extensions generate the highest returns at $1.80 to $2.20 for every dollar invested, while bathroom extensions return $1.50 to $1.90 per dollar spent. Open-plan living extensions consistently outperform bedroom additions, with family-focused spaces delivering premium resale values across Melbourne’s established suburbs.

Smart Design Maximises Every Dollar

Design efficiency creates exceptional value without inflated costs. Combined kitchen, dining, and living spaces in one extension reduce per-square-metre costs by 20-25% compared to separate room additions, while creating the open-plan living Melbourne buyers demand. Extensions positioned to capture northern light eliminate expensive artificial lighting during peak hours and reduce ongoing energy costs. We recommend extensions that connect seamlessly with existing spaces rather than isolated rooms, as integrated designs deliver higher resale values and better family functionality. Built-in storage incorporated during construction costs 60% less than retrofitted storage solutions later.

Professional Builders Prevent Costly Mistakes

Experienced extension builders identify potential issues during the planning phase that inexperienced contractors miss, saving homeowners $15,000 to $40,000 in rectification costs. Professional builders secure competitive material prices through established supplier relationships, typically reducing material costs by 10-15% compared to homeowner direct purchases. Quality builders complete extensions 3-4 weeks faster than industry averages, reducing temporary accommodation costs and minimising family disruption. Professional builders handle complex council interactions and building compliance requirements that prevent expensive delays or failed inspections (which can add months to project timelines).

Return on Investment by Extension Type

Rear extensions that expand kitchen and living areas consistently deliver the strongest returns, particularly in Melbourne’s inner and middle suburbs where outdoor space commands premium values. Side return extensions work exceptionally well for Victorian and Edwardian homes, typically adding $80,000 to $150,000 in value for a $60,000 to $100,000 investment. Wrap-around extensions suit larger blocks and deliver substantial value increases, though they require higher initial investments ($120,000 to $200,000) that appeal to specific buyer demographics.

Final Thoughts

Single storey extension cost calculations require homeowners to understand Melbourne’s $2,200 to $3,500 per square metre market rates, though actual investment varies based on site conditions, material choices, and council requirements. Extensions deliver strong returns when homeowners plan strategically, with kitchen-focused additions that generate $1.80 to $2.20 for every dollar invested. Professional builders prevent costly mistakes that inexperienced contractors often miss during construction.

Quality builders identify potential issues during the initial assessment phase, secure competitive material prices through established supplier relationships, and complete projects faster while they handle complex council requirements. Professional assessment reveals true project costs and identifies value-maximisation strategies specific to your property and family needs. Detailed quotes from experienced builders who understand Melbourne’s diverse soil conditions help homeowners make informed decisions.

Cameron Construction specialises in ground floor extensions and premium renovations across Melbourne’s councils. We handle projects from concept to completion, including all necessary permits and compliance requirements (with over four decades of local experience). Contact us for professional assessment of your extension project and detailed cost estimates.