Construction Cost Calculator

How to Use the Construction Cost Calculator

A quick guide to getting realistic estimates for your Central Coast project

Getting Started

The HD2 Construction Calculator is a helpful starting point for understanding build costs. Here's how to get accurate estimates for your project here

Step 1: Choose Your Build Type

Select "Custom/Architectural Build" — this reflects the quality and detail of professionally designed homes.

(Avoid "Project Home" unless you're comparing basic costs.)

Step 2: Enter Your Build Size

Include:

  • All internal living areas

  • Attached garage

  • Covered alfresco areas (count as 50% of area)

Don't include:

  • Uncovered decks or paths

  • Unenclosed carports

Step 3: Adjust for Central Coast Conditions

The calculator gives base costs. Add these percentages for site-specific challenges:

Flood Zone Properties: +15–20%

  • Raised floor levels

  • Flood-resistant materials

  • Enhanced drainage

Bushfire Zones (BAL Rated): +10–15%

  • BAL 12.5/19: +10%

  • BAL 29/40: +15%

  • Fire-rated materials and construction details

Sloping Sites:

  • Gentle slope (1:10): +5–10%

  • Moderate slope (1:8): +10–15%

  • Steep slope (1:6 or greater): +15–25%

Waterfront Properties: +10–15%

  • Acid sulphate soil management

  • Marine-grade materials

  • Additional engineering

Step 4: Don't Forget Additional Costs

Design & Documentation: 8–12% of build cost

  • Architectural design

  • Engineering

  • Consultant reports

Council & Approvals: $5,000–$15,000

  • DA or CDC fees

  • BASIX certificate

  • Construction Certificate

Site Costs: Variable

  • Demolition (if needed): $15,000–$30,000

  • Tree removal: $1,000–$5,000 per tree

  • Site clearing: $5,000–$15,000

Always include: 10–15% contingency

Example Calculation

4-bedroom home in Matcham (bushfire zone, gentle slope):

Base build (200m²): $400,000
Bushfire (BAL 19): +10% = $40,000
Slope adjustment: +8% = $32,000
Subtotal: $472,000

Design & approvals: $65,000
Contingency (10%): $47,200
Total Budget: $584,200

Important Notes

  • Costs are estimates only — Every site is unique

  • Prices change — Construction costs typically rise 5–10% annually

  • Quality matters — Cheaper isn't always better, especially for challenging sites

  • GST included — Calculator includes GST in estimates

Next Steps

  1. Use the calculator to get your baseline estimate

  2. Apply the adjustments above for your site

  3. Book a consultation — I'll refine these numbers based on your specific property

At your $295 consultation, I'll provide more accurate guidance based on your exact site conditions, current local builder pricing, and your specific design requirements.

Try the Calculator

Pro tip: Good design can often reduce construction costs by working cleverly with your site. That's where thoughtful planning really pays off.

Getting started