The short answer: a quality custom home in North-West Sydney (Box Hill, Castle Hill, Kellyville, The Gables and surrounds) costs $3,500–$5,500 per square metre to build in 2026, putting a typical 280m² family home in the $1.0M–$1.5M range before siteworks, demolition or landscaping. Luxury custom builds move past $6,000/m².
What moves the number most: soil class (Wianamatta clay can swing slab costs by $30–40k), structural complexity, selections, and how many provisional sums sit inside the headline "fixed price." A genuine fixed-price quote has site investigation and selections completed before contract — not deferred to construction.
Everyone wants a number. Almost no builder will give you one in writing before a site visit. We understand why — but we also think we can be more useful than "it depends".
So here's our honest read of what a quality custom build in North-West Sydney looks like in 2026, the variables that move it, and where most quotes quietly hide their weak spots.
A working range, with caveats
For a well-specified custom home in Box Hill, Castle Hill, Kellyville, the Gables and surrounds, current build costs typically sit between $3,500 and $5,500 per square metre. Luxury custom — premium stone, bespoke joinery throughout, imported tapware, structural complexity — comfortably moves past $6,000/m².
A 280m² family home, mid-range custom, is therefore most often in the $1.0M – $1.5M territory — before the slab, before the demolition (if it's a knockdown rebuild), and before landscaping.
The cost-per-m² number is a useful sanity check, not a quote. The factors below are what actually drive the figure on a given site.
Where the money goes
Site works and slab. Wianamatta clay across the North West Growth Area frequently classifies as M, H1 or H2 under AS 2870. A waffle pod on a Class M site might be $35–$50k. A properly engineered raft on Class H1 can push past $70k for the same footprint. Have your site classified before a contract is written.
BASIX and the 7-star NatHERS baseline. Since the NSW BASIX update, all new dwellings must hit a 7-star thermal rating. Insulation, double glazing where it matters, and considered orientation are no longer upgrades — they're the floor. Budget roughly $15–$30k vs a pre-2023 spec.
Structural complexity. Two-storey adds engineering and trade time. Cantilevers, raked ceilings, big spans of glazing — each one carries a real cost.
Selections. Kitchens, bathrooms, joinery and stone are where mid-range becomes high-end fast. A genuine fixed-price quote will have most of this specified before you sign.
Knockdown rebuild adds. Demolition of a 1970s–80s Hills brick veneer typically runs $25–$45k once asbestos is properly handled. Add temporary accommodation while you build.
The hidden variables
A few things we see catching people out:
- Provisional sums that absorb 8–12% of a contract — site costs, drainage, landscaping. Genuine fixed-price contracts keep these to a minimum.
- Council differences. Box Hill straddles Hills Shire and Blacktown. Marsden Park is Blacktown. North Richmond is Hawkesbury. Different DA timelines, different Section 7.11 contributions.
- Long-lead items. Bespoke joinery, imported windows and stone can run 10–16 weeks. Designing around them late in the program costs money.
How we quote it
We do the soil classification, full site investigation, and selections up front. Then we write a fixed price with as few PS and PC items as possible — and we tell you exactly what each one is and why. You can see what's in a Macan price on our inclusions page.
If you'd like a serious conversation about what your site and brief would actually cost, start there. We'd rather quote slowly and accurately than quickly and convenient.
