Project Cost Guide
Understanding the Real Costs of Building on the Central Coast
Design Investment
My design fees:
Granny flat/Studio: $3,500–$5,000
Single-storey renovation/addition: $6,000–$9,000
Two-storey renovation/addition: $9,000–$12,000
New home (3–4 bed): $12,000–$18,000
Large/complex new home: $18,000–$25,000
All fees are fixed-price and include:
Concept design through to approval documentation
Project dashboard access
Unlimited revisions during concept phase
Council/CDC submission assistance
Construction Budgets
Base Construction Costs (2024/25):
Use the HD2 Construction Calculator for detailed estimates.
Typical Central Coast ranges:
Basic: $1,800–$2,200/m²
Standard: $2,200–$2,800/m²
Premium: $2,800–$4,000+/m²
Site-Specific Cost Adjustments
Flood Zone Properties: +15–20%
Raised floor systems
Flood-resistant materials
Enhanced drainage
Engineering requirements
Bushfire Zones (BAL):
BAL 12.5/19: +10%
BAL 29: +12%
BAL 40: +15%
Fire-rated materials and construction
Sloping Sites:
Gentle (up to 1:10): +5–10%
Moderate (1:8): +10–15%
Steep (1:6 or greater): +15–25%
Retaining walls and structural requirements
Waterfront Properties: +10–15%
Acid sulphate soil management
Marine-grade materials
Additional engineering
Additional Project Costs
Council & Approval Fees:
DA application: $1,500–$3,000
CDC application: $1,000–$2,000
BASIX certificate: $300–$600
Construction Certificate: $1,500–$3,000
Consultant Fees (if required):
Structural engineer: $3,000–$8,000
Surveyor: $1,500–$3,500
Bushfire consultant: $800–$1,500
Arborist report: $600–$1,200
Geotechnical report: $2,000–$4,000
Site Preparation:
Demolition: $15,000–$30,000
Tree removal: $1,000–$5,000 per tree
Site clearing: $5,000–$15,000
Temporary fencing: $2,000–$3,000
Example Project Budgets
Granny Flat (60m²) - Flood Zone:
Design: $4,000
Construction (base): $150,000
Flood adjustment: $22,500
Approvals & consultants: $8,000
Total: $184,500
Family Home Renovation (100m² addition):
Design: $8,000
Construction: $250,000
Approvals & consultants: $10,000
Council contributions: $10,000+
Site costs: $5,000
Total: $283,000
New 4-Bedroom Home (220m²) - Sloping Site:
Design: $15,000
Construction (base): $550,000
Slope adjustment (15%): $82,500
Approvals & consultants: $15,000
Site preparation: $20,000
Total: $682,500
Budget Planning Tips
Always Include:
10–15% contingency fund
GST (included in most quotes)
Moving/storage costs
Temporary accommodation if needed
Ways to Manage Costs:
Engage your builder during design phase
Stage construction over time
Choose standard materials where possible
Keep existing plumbing locations
Minimise structural changes
Payment Schedules
Design Fees (typical):
25% on engagement
35% at concept design
30% at documentation
10% at submission
Construction (typical):
5% deposit
Progress payments per stage
5% retention at completion
Ready to Get Specific?
Every site is unique. For accurate pricing tailored to your property, book your $295 consultation — I'll provide detailed cost guidance specific to your site's challenges and your family's needs.
Questions about costs? Call me on 0450 298 701 or sarah@oandcodesigns.com.au