Sitework is the line item that ruins more first-region builds than any other. Frames are easy to estimate. Cabinetry is easy. Roofing is easy. Sitework is the one that hides.
I have worked across Geelong, the Bellarine Peninsula and the western Melbourne fringe for over two decades. Every time we open a job in a suburb we have not built in before, the first sitework estimate is wrong. Not by a small amount.
What sitework actually contains
When estimators talk about sitework they usually mean four things bundled together:
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- Bulk excavation and benching
- Stormwater and sewer connection works
- Retaining walls, where required by site fall
- Site clean and disposal at completion
In urban infill blocks across Melbourne and Geelong, these four items together usually run between 4% and 7% of the contract value on a custom home. On a knockdown rebuild the percentage is higher because of demolition, asbestos clearance and sometimes contaminated soil.
The trap is not the average. The trap is the variance between sites.
Why the variance is so wide
Two blocks 800 metres apart can have wildly different sitework costs. The variables we have measured the most impact from:
Site fall. A 1-in-30 fall on a 600 m² block is benign. The same fall on a long narrow block over 35 metres becomes a retaining problem. The cost to retain a 1.2 metre cut runs $850 to $1,400 per linear metre depending on engineering and material choice. A 50-metre block with a 1.2 metre cut on one side is $42,000 to $70,000 of retaining alone.
Soil class. P-classified sites trigger engineered slabs and frequently engineered piers. A waffle pod slab on M-class costs around $98 per m² placed in 2024 prices in the Geelong region. The same footprint on P-class with bored piers can run $145 to $180 per m². On a 220 m² footprint that is $10,000 to $18,000 of unanticipated cost if you priced for M-class.
Stormwater connection point distance. Council-mandated connection point on a long block can mean 25 to 40 metres of stormwater pipe through landscaped or finished surface. At $120 to $180 per linear metre installed in tight access, the connection alone can be $3,000 to $7,000 over what you would have priced as a typical urban infill.
Tree removal and protection. Significant tree exclusion zones in the City of Greater Geelong and most metro councils require an arborist report and tree protection fencing through the entire build. A single retained tree adds $2,500 to $4,500 in protection costs and sometimes triggers a redesign of stormwater and excavation paths.
The cost of getting it wrong
Sitework is almost always priced before the soil report and the survey come back. Builders use a per-m² rate that worked on the last job. The first job in a new suburb is usually wrong by between $8,000 and $35,000 against actuals. On a custom home with an 18% margin that is between half a percent and 2% of the entire contract margin, gone before the slab is poured.
The pattern is consistent across every region we have data on.
The first job in a new suburb is the job you make mistakes on. The trick is to price it like you have already made them.
What to do instead
We use a three-step process for any job in a region we have not previously built in.
One. Pull the sitework actuals from the closest comparable jobs we have, by build type and block size. If we have no closely comparable data we use the regional rolling average for the suburb if available.
Two. Add a regional unfamiliarity loading on the four sitework line items. The loading is 8% to 15% depending on how confident we are in the data set. The loading is visible to the client and explained in the assumption log.
Three. Caveat the sitework allowance in the contract until soil reports, surveys and council connection points are confirmed. The caveat language gives both sides the right to revise the sitework allowance based on actual site conditions before slab.
We have not lost a job to this loading. We have stopped losing margin to sitework.
What the data shows
Across our last 24 months of completed jobs in the Geelong and western Melbourne regions, the average overrun on sitework on first-region jobs was 22% above the original allowance. The average overrun on second-and-subsequent jobs in the same region dropped to 6%.
The data tells you exactly what is happening. The first job you teach yourself the region. The second job you price the region.
The point of running a cost intelligence platform is to teach yourself the region before the first job, not after it.
If your business is moving into a new postcode this year, the single most expensive line item to get wrong is the one nobody pays attention to. Sitework is where margin disappears in November and reappears as a hard conversation in March. Price it like you already know what it costs. Then go and find out.
