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What are site costs when building a house?

Site costs are charges above the base price related to preparing your block for construction — soil testing, site levelling, slab upgrades, retaining walls, drainage, connections and other site-specific requirements.

How much should I budget for site costs?

A conservative buffer is $15,000–$30,000 on a typical suburban block. Sloping or reactive soil sites can exceed $50,000+. Always get a site-specific assessment before finalising your budget.

Are site costs included in a builder's base price?

Rarely. Most volume builder base prices include a small nominal site cost allowance. The actual amount is determined after a site survey and soil test, and differences are charged as extras.

What is a provisional sum for site costs?

A provisional sum is an estimated allowance in your contract for site costs that haven't been fully determined yet. If the actual cost is higher, you pay the difference. Always ask for fixed-price site costs where possible.

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Home›Build Knowledge Hub›Building Process›Slabs & Siteworks›Site Costs Explained

Slabs & Siteworks

Site Costs Explained

What site costs actually cover, why they vary so much, and how to protect your budget before signing a building contract.

6 min·Compare My Build — Independent Resource· Updated June 2025

Introduction

Site costs are the costs incurred to prepare your specific block of land for construction. They are almost never included in a builder's advertised base price — and are one of the most common causes of new build budget blowouts. Understanding what site costs cover, how they're calculated, and how to minimise surprises is essential before signing any building contract.

What Site Costs Cover

Cost Item	What It Covers
Geotechnical report	Soil classification and bearing capacity testing
Slab upgrade	Upgraded slab type based on soil classification
Cut and fill / earthworks	Levelling a sloping or uneven site
Retaining walls	Structural walls to hold soil on sloping blocks
Drainage	Surface and sub-surface drainage for water management
Service connections	Connecting power, water, sewer and gas to the block
Driveway crossover	Kerb cut and crossover to the property boundary
Demolition	Removing existing structures if subdividing or rebuilding

Typical Site Cost Ranges

Cost Comparison

Flat M class site (best case)$5,000 – $12,000

Typical suburban block (H1, mild slope)$12,000 – $25,000

Sloping block with retaining walls$25,000 – $50,000+

Rocky sites or P class soils$30,000 – $80,000+

Service connections (rural)$5,000 – $25,000 extra

Site costs vary dramatically by location, block, and builder. Never sign based on an assumed nominal allowance.

Common Builder Inclusions

›Most builders include a nominal $5,000–$10,000 site cost allowance in their base price
›Actual site costs are determined after soil testing and site survey — not before
›Provisional Sums are commonly used — and commonly blow out
›Fixed-price site cost offers do exist — ask specifically if your builder can provide one
›Some builders offer 'full fixed price' contracts that lock in site costs — worth seeking

Common Trap

A builder advertising a $350,000 base price with a $5,000 site cost allowance may end up costing you $395,000 once actual site costs are determined. Always ask: "What is your maximum site cost exposure on this contract?"