What Is the Cost To Dig Out a Basement?

What Is the Cost To Dig Out a Basement?

Is it possible to dig out a basement to increase the square footage and resale value of a home? If so, how much would it cost In Australia, basement excavation typically ranges from $1,500 to $3,500 per square metre, with final costs depending on soil type, depth, waterproofing, and finishes. 

This guide dives into:

  • Key factors affecting basement digging costs.
  • Hidden fees to anticipate (and how to avoid them).
  • DIY vs. professional excavation risks.
  • Why Substructure Solutions is your trusted partner for compliant, cost-effective projects.

Breaking Down Basement Excavation Costs

1. Site Conditions

  • Soil Type:
    • Soft/ Sandy Soil: $1,200–$2,000 per m² (easy to dig).
    • Rocky/ Clay Soil: $2,500–$4,000+ per m² (requires jackhammers or blasting).
  • Water Table: High groundwater levels demand sump pumps and drainage systems (+$5,000–$15,000).
  • Access: Tight urban sites may need smaller machinery, increasing labour time.

2. Project Scope

  • Size: A 30m² basement costs $45,000–$105,000; larger spaces benefit from economies of scale.
  • Depth: Digging deeper than 2m often requires engineering approvals and reinforced walls (+20–30%).

3. Underpinning Existing Structures

Excavating under a standing home (“underpinning”) involves temporary supports and staged digging to prevent cracks. Adds $20,000–$50,000+ depending on foundation type.

4. Waterproofing & Utilities

  • Basic Waterproofing: Membranes and French drains (80–150/m²).
  • Full Climate Control: HVAC, insulation, and ventilation (+$10,000–$30,000).

5. Finishes

  • Unfinished Shell: $1,500–$2,500 per m² (concrete walls, basic flooring).
  • Turnkey Living Space: $3,000–$5,000+ per m² (lighting, plumbing, flooring).

DIY vs. Professional Basement Excavation: What’s the Real Cost?

The DIY Myth

While DIY digging might seem cheaper, risks include:

  • Safety Hazards: Unsupported trenches can collapse—Australia averages 15 excavation-related fatalities annually.
  • Costly Mistakes: Misjudging soil stability or drainage can lead to floods or structural damage (+$10,000–$50,000 repairs).
  • Permit Pitfalls: Councils require engineering certifications and inspections; DIYers often face delays or fines.

Why Hire a Professional?

Reputable contractors offer accurate quotes upfront. You don’t need to worry about hidden fees and costs. Professionals factor in permits, waste removal and advanced machinery. With the pros, you can also ensure that only the most advanced techniques are used to complete the project, including hydro excavation, laser-guided digging, and non-invasive methods protect your property. With professionals, you can guarantee compliance for they handle all the paperwork for you, including BASIX certifications and council approvals.

5 Hidden Costs to Plan For

  1. Council Permits: $1,000–$5,000 (varies by state).
  2. Soil Testing: Geotechnical reports cost $500–$2,000 but prevent costly errors.
  3. Waste Removal: Disposing of 100m³ of soil averages $3,000–$7,000.
  4. Unexpected Obstacles: Tree roots, buried pipes, or rock shelves add $3,000–$15,000.
  5. Post-Construction Fixes: Cracks from settling soil or poor waterproofing (+$5,000–$20,000).

How to Save on Basement Digging Costs

  1. Optimise Design - Smaller footprints and simple shapes reduce excavation time.
  2. Phase the Build - Complete structural work first, add finishes later.
  3. Bundle Services - Pair basement excavation with foundation repairs or landscaping.
  4. Choose Smart Materials - Concrete blocks over poured walls can save 10–15%.

Why Trust Substructure Solutions?

With 15+ years of specialised experience, we’ve delivered 300+ basement projects across Australia. 

Our edge:

Licensed Engineers

All projects meet AS 2870 (residential slabs and footings) standards.

Fixed-Price Contracts

No hidden charges—quotes include GST, permits, and inspections.

Cutting-Edge Tech

3D modelling ensures precise digging; moisture sensors prevent future leaks.

Proven Track Record

High client satisfaction rate, with projects completed on time and budget.

Real-World Cost Example

Project: Digging a 40m² basement under a Sydney terrace home.

  • Excavation: 2,800/m² x 40m²=$112,000.
  • Underpinning: $35,000.
  • Waterproofing: $12,000.
  • Basic Finishes: $60,000.

Total: $219,000.

Ready to Start Your Project?

Digging out a basement is a major investment, but with expert planning, it can transform your home’s functionality and resale value. In order to create a space that will last, it is important to be aware of the factors that affect costs and to work with a reliable expert, such as Substructure Solutions. 

Contact Substructure Solutions today for a free site assessment and detailed quote. Let’s turn your basement vision into reality—safely, smoothly, and stress-free.

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