What is the most expensive part of building a house?

How a Sydney build budget breaks down

Sydney Home Renovation's January 2026 guide ranks the main costs of a new Sydney home as a share of construction cost, with land left out. Its figures are one builder's estimates rather than an official survey, so treat them as a guide to the order of costs rather than a budget.

• Framing, roofing and structure take 25 to 35 per cent of the build.
• Interior finishes take 15 to 20 per cent, about the same as the electrical, plumbing and air conditioning services.
• The foundation and slab take 10 to 15 per cent.
• The exterior envelope and windows take another 10 to 15 per cent.
• Site work, approvals and professional fees make up the last 10 to 15 per cent.

The structure leads because it needs a large volume of material, skilled labour and weeks on site all at once. The same guide puts structural timber for an average Sydney home at $45,000 to $90,000 in materials alone. Framing labour adds another $40,000 to $85,000, depending on the roof and how complex the plan is.

Where the money goes on a custom home in Sydney

On a custom home the most expensive part of building a house shifts with the site and the specification. Sydney Home Renovation estimates that a moderately sloped block adds $40,000 to $90,000 in site work before framing starts, while a steep one can add $110,000 to $230,000. Sandstone, common across much of Sydney, adds $150 to $400 for every cubic metre of rock removed.

The design matters as much as the site. Large openings, cantilevers and long spans need steel and engineering that a simpler plan would avoid. Multiple roof planes and changing ceiling heights also add labour to every stage of the frame.

The finishes then decide how far the budget stretches because they are where your own choices move the number most. On the homes we build, finishes are where costs most often run past the budget, even though the structure takes the larger share. That is why our architecture and interior design sit in house with construction, so every selection is priced against the brief while it is still being drawn. CPP Quantity Surveyors' 2026 Sydney guide places architecturally designed homes with premium finishes at $4,500 to $10,000 per square metre and above. The range is wide because stone, joinery, glazing systems and appliances vary so much in price. Land, design fees, approvals and landscaping sit outside those construction figures. Our guide to the cost to build a house in Sydney shows how to bring them into one budget.

How a NSW building contract is paid

A home building contract in NSW is paid in stages as the work reaches agreed points, from the slab and frame through to lock-up, fixing and completion. NSW law caps the deposit at 10 per cent of the contract price, while the share paid at each later stage is set in your own contract. Read that payment schedule closely, because matching each claim to the work it pays for is easier once you know which parts of the build carry the most cost.

How do you keep the most expensive parts under control?

The structure is the hardest part of a house to change later, so it deserves the most planning time. A soils report and survey before design show what the site will ask of the foundations. A clear footprint, consistent ceiling heights and a resolved roof then keep the frame efficient without making the home ordinary.

Name the finishes early, because a generous allowance for one kitchen can fall well short for another. Prime cost items cover the supply of selections still to be made, while provisional sums cover work that could not be priced when the contract was signed. Ask what each allowance includes before you compare quotes. Our new home selections checklist sets out what to record for each finish so the price and the program stay aligned.

When design, interiors and construction sit in one practice, our builders can price these choices while the drawings are still easy to change. If you are planning a new home, see how we approach custom homes in Sydney from the site and brief through to handover.