The line items that regularly blow new build budgets — and how to protect yourself before you sign a contract.
Last updated: 14 July 2026 · 927 words
SOURCE · PROFESSIONALS
Find a licensed builder or architect near you
As of 14 July 2026, 57,692 — Development applications indexed from the NSW Planning Portal public register (NSW Planning Portal)
As of 14 July 2026, 128 — Every NSW council's development applications, updated daily (NSW Planning Portal)
As of 14 July 2026, 18 — Construction material prices benchmarked against ABS producer price movements (ABS PPI 6427.0)
Signing a fixed-price building contract feels like certainty, but most new home budgets in Australia run over — not because builders are dishonest, but because the contract price and the total project cost are two genuinely different things. Understanding the gap before you sign is the single most effective way to protect your finances.
Why the Contract Price Is Never the Full Price
Volume builders in particular price their base contracts to be competitive at the display-home stage. Inclusions are carefully scoped, site conditions are assumed to be standard, and dozens of necessary costs sit outside the contract entirely. By the time you reach practical completion, these extras routinely add 15–30% on top of the headline figure — sometimes more on challenging sites or in regional areas.
The costs below are not edge cases. They appear on the majority of new builds across New South Wales, Victoria, Queensland and beyond, yet many buyers only discover them after contracts are exchanged.
Site Costs and Soil Reports
Every builder requires a geotechnical (soil) report before finalising site costs. If your block has reactive clay, rock, fill, poor drainage or a high water table, the slab and footings must be engineered accordingly. Site costs on a straightforward flat block in a new estate might add $8,000–$18,000 (indicative) to your contract; a sloping, rocky or flood-affected site can push that figure to $40,000–$80,000 or more (indicative). Always request a fixed site-cost assessment based on an actual soil test — not a standard allowance — before you sign.
Connections and Service Upgrades
Connecting water, sewer, stormwater, electricity and gas to the boundary is rarely included in a base contract. In established suburbs these services may already be close; on greenfield land or rural lots the trenching and connection fees can be substantial. Underground power upgrades, NBN pit relocation, and council-required stormwater detention systems are common surprises. Budget a $5,000–$25,000 (indicative) allowance and get written confirmation from each utility provider before settlement.
Development Application and Certification Fees
Depending on your council and project type, you will pay either a Development Application (DA) through your local council or a Complying Development Certificate (CDC) through a private certifier. Neither is free. DA fees vary by council and project value; CDC fees are set by certifiers but still significant. Add council infrastructure contributions (also called Section 7.11 or similar levies depending on your state) which can reach $10,000–$30,000+ (indicative) in growth corridors. In New South Wales, BASIX certificates for energy and water efficiency are also a mandatory cost to factor in.
Landscaping, Driveways and Fencing
The NCC requires a habitable, weatherproof structure — not a finished yard. Standard contracts typically end at the edge of the slab or at a nominal turf allowance. Completing the exterior to a liveable standard — driveway, paths, retaining walls, front and side fencing, lawn and garden beds — commonly adds $20,000–$60,000 (indicative) depending on block size, slope and materials. Council conditions may also mandate specific fencing heights or materials along boundary types.
Floor Coverings, Window Furnishings and Appliances
Many fixed-price contracts include only a modest tile or carpet allowance. If your selected finishes exceed that allowance — which is easy to do — you pay the difference as a variation. Window furnishings (blinds, curtains) are almost universally excluded. Confirm exactly what is included in writing, and price the gap to your actual specification before signing.
Upgrade Variations During Construction
Builders earn meaningful margin on variations. Changes to electrical layouts, additional downlights, upgraded tapware, or a relocated wall after the contract is signed are charged at rates that reflect this. Variations during the frame stage and beyond also slow the build. The discipline required is to lock in your full specification — including a thorough interior design session — before the contract is executed, not during construction.
Temporary Accommodation and Holding Costs
New home timelines in Australia currently run to 12–24 months from contract to handover in many markets, partly due to trade availability and material supply. If you are selling an existing home to fund the build, you need to fund rent or bridging finance for that period. Bridging loan interest, rent, storage, and the carrying costs of land while you wait all erode budget that buyers rarely account for at the planning stage.
Insurance During Construction
Your builder is required to hold Home Warranty Insurance (called Home Building Compensation in NSW, Domestic Building Insurance in Victoria) for projects above relevant thresholds. However, you should also confirm your own contract works and public liability cover, and arrange home and contents insurance before handover. These are separate costs with separate providers.
A Practical Pre-Contract Checklist
- Obtain an actual soil test and fixed site-cost assessment — not a standard allowance
- Confirm all utility connection costs in writing with each provider
- Request a full inclusions schedule and check every finish allowance against your real choices
- Ask the certifier or council for an indicative DA/CDC and infrastructure contribution estimate
- Get three quotes for landscaping, fencing and driveway before you set your budget
- Model the holding cost scenario: what if the build takes six months longer than forecast?
- Review the contract with a solicitor experienced in residential construction, not a general conveyancer
How the Numbers Stack Up
| Cost Category | Indicative Range | Often in Base Contract? |
|---|---|---|
| Site costs and footings | $8,000–$80,000+ | Partially (with allowances) |
| Utility connections | $5,000–$25,000 | Rarely |
| DA/CDC and levies | $5,000–$30,000+ | No |
| Landscaping, fencing, driveway | $20,000–$60,000 | No |
| Flooring and window furnishings | $8,000–$25,000 | Allowance only |
| Holding costs and accommodation | Varies significantly | No |
Use the DesignBuildSource cost estimator to model your full project budget, or search our builder directory to find HIA-member builders in your suburb who provide transparent all-inclusive quoting.
BUILD · CALCULATOR
Estimate your build cost in 60 seconds
State multipliers · 7 build types · Compliance disclaimer included
FREQUENTLY ASKED
What are provisional sums in a building contract?
Provisional sums (PS) are the builder's estimated cost for work items where the final price cannot be confirmed at contract signing — typically rock excavation, retaining walls, stormwater management, and connection fees. If the actual cost exceeds the PS allowance, you pay the difference. Provisional sums should be itemised in the contract; a lump-sum PS is a significant red flag.
What are prime cost items in a building contract?
Prime cost (PC) items are contract allowances for fixtures and fittings you'll select later — tapware, door hardware, tiles, floor coverings, light fittings, and appliances. Volume builder PC allowances are frequently below the cost of the products shown in display homes. Review every PC item, price your actual selections, and negotiate increased PC allowances before signing.
What are Section 7.11 developer contributions in NSW?
Section 7.11 contributions (formerly Section 94) are fees levied by NSW councils on new development to fund local infrastructure — roads, parks, drainage, and community facilities. They are calculated as a percentage of the development cost or on a per-lot basis. In growth corridors, they typically add $10,000–$40,000 per dwelling and are paid before a construction certificate is issued.
What connection fees apply to a new home in NSW?
Connecting a new NSW home to water, sewer, electricity, gas, and NBN involves separate fees from the relevant utility providers. Water and sewer connections with Sydney Water typically cost $4,000–$12,000 depending on the service area and distance. Electricity connection fees vary by network distributor and meter type. Budget $8,000–$25,000 in total connection costs, all excluded from the builder's contract.
How much should I budget for landscaping on a new build?
A complete external finish on a standard suburban new build — driveway, paths, lawn, basic planting, letterbox, clothesline, and fencing — typically costs $20,000–$60,000 beyond the builder's contract. Fencing alone averages $8,000–$25,000 for a full block perimeter. These items are almost universally excluded from volume builder base prices.
NEXT STEP
Get formal quotes from verified professionals
Design Build Source lists Australian builders, architects and designers, with licence details displayed from public register data where available.
DBS Editorial
Design Build Source — Australia's construction intelligence platform. Data sourced from ABS, council DA registers, and verified professional quotes.
This guide is for general information only and does not constitute professional advice. Cost figures are indicative estimates based on the DBS Real Cost Database and ABS Producer Price Indexes. Always obtain independent advice from a licensed builder, quantity surveyor, or financial adviser before making construction or financial decisions. Build costs vary significantly by site, design, finish level, and location.
