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Site works — the costs that are not in the base price

From Modular Living Australia — the independent knowledge base Last updated: 8 Oct 2026

Site works are not included in a modular home's base price, and published estimates vary widely: a soil test about A$400–A$1,500, site preparation about A$10,000–A$18,000 on a flat block and A$45,000–A$180,000 on a sloping or difficult one, and service connections about A$7,600–A$30,600.^{[1][2][3][4][5]} Crane hire is put at about A$260–A$1,530 per hour with four- to ten-hour minimums.^[5] These are commercial guidance, not independent survey data.

A modular home's advertised price is a factory price. It buys the building. It does not buy the ground it stands on, the hole it sits in, the crane that lifts it, the pipes that reach it or the paperwork that permits it. One published NSW cost guide states plainly that a quoted rate per square metre typically refers to the building envelope only — foundations, frame, roof and internal fit-out to a standard specification.^[4]

The gap between the advertised figure and the final invoice is called site works, and it is the single largest source of budget surprise in Australian residential construction. Published estimates for the same category of work differ by an order of magnitude, because the answer genuinely depends on the block.

There is no standard definition of what "site works" covers, which is the first problem when comparing quotes. Published guides describe the category as covering site preparation, clearing, excavation, retaining walls, drainage, piering for reactive soils and utility connections.^[3][2] Modular-specific guidance adds soil testing, engineering, transport, crane hire, service connections and approvals to the list of items sitting outside the advertised price.^[5] For an off-site build the list divides usefully into three groups: ground works (soil investigation, engineering, excavation, retaining, footings and slab or piers); access and delivery (whether a semi-trailer and crane can physically reach the build position — covered separately in delivery, transport and craneage); and connections and approvals (water, sewer or on-site wastewater, power, stormwater, and council certificates and contributions).

Why the ranges are so wide §

Published cost guides do not agree with each other, and none of them is an independent survey. One 2026 guide reports site preparation — excavation, retaining walls, drainage and piering — at about A$18,000 for a flat suburban Brisbane block and A$60,000 to $90,000 for a sloping Sydney North Shore block.^[3] A separate NSW guide puts land preparation at A$45,000 to $180,000, covering demolition, tree removal, soil testing, excavation, cut-and-fill earthworks, retaining walls and temporary site access.^[4] A third guide puts a flat block with good soil at about A$10,000 and a sloping block with reactive clay at A$45,000 or more.^[2] A fourth, modular-specific guide takes a different approach again and reports site preparation and utility connections as adding 10 to 20 per cent to base module costs.^[7]

These are not compatible estimates and should not be averaged. They describe different site conditions, different scopes and different states. What they agree on is direction: flat, serviced, accessible suburban blocks sit at the bottom of every range; sloping, unserviced or constrained blocks sit at the top.

Before anything is built: reports and certificates §

Soil test and site classification A geotechnical investigation and written report classifying the soil under AS 2870, reported at A$400 to $1,500, with most standard suburban blocks in the A$500 to $900 range.^[1] Trade guidance states that a building certifier cannot approve plans without a current, site-specific classification report.^[8]

Site feature survey Levels, boundaries, existing structures, trees and services. Listed as a separate budget item in modular cost guidance.^[5]

Engineering Footing and slab design, which follows from the soil classification rather than preceding it.^[5]

Energy assessment In NSW a BASIX certificate is required before lodging a development application or complying development certificate for a new dwelling; lodging without one triggers a request for further information that pauses the assessment.^[9] Elsewhere a NatHERS assessment fills the equivalent role.^[3]

Wind classification An AS 4055 wind classification can be carried out during the same site visit as the soil test.^[8]

The soil test is the cheapest item on this list and the one that determines the most expensive. Commercial guidance describes the common failure mode directly: a contract is signed with a site-cost provisional sum based on assumed good soil, the test returns a highly reactive classification, and the foundation budget is exceeded before any concrete is poured.^[1]

A quote issued before the soil report is a quote with a hole in it. The number in the site-works line is an assumption, and assumptions in building contracts are usually written as provisional sums — meaning the buyer pays the difference if the assumption was wrong.

Site classification and what it does to the foundation §

The National Construction Code classifies sites by foundation soil type and refers to AS 2870 for the detailed differentiation.^[6] The classes describe how much the ground is expected to move as its moisture content changes:

Two points are often misunderstood. First, a P classification is not a finding that the site is unbuildable — it indicates site-specific conditions that require the engineer's consideration.^[8] Second, for classes M, H and E the code applies a further division based on the depth of expected soil movement, producing M-D, H-D and E-D classifications where deep-seated movement applies.^[6]

The cost consequence is direct but, again, disputed between sources. One NSW guide reports that reactive soil conditions requiring reinforced waffle slabs or pier systems add A$15,000 to $35,000 to basic slab costs.^[4] A different guide puts the additional cost of deeper footings on Class H or E ground at roughly A$5,000–$20,000,^[2] while a third cites about A$8,000–$25,000 in piering for H2 or P-class sites.^[3] Treat any site-works allowance quoted before the soil report as provisional — none of these figures apply until your own site has been tested.

The two foundation figures above disagree substantially — A$12,000–$20,000 for a two-bedroom slab against A$55,000–$95,000 for a 200 m² home. Part of that is dwelling size, part is scope definition, and part is that neither figure is drawn from a survey. All are published by companies with a commercial interest in the answer.

Why this matters more for modular, not less §

Off-site construction shortens the factory half of the programme — published guidance describes factory manufacturing windows of about 8 to 14 weeks^[10] — but it does nothing to shorten or cheapen the site half. Two consequences follow.

First, the site work has to be finished before the modules arrive. In a conventional build, footings and services are the start of a long sequence and any delay is absorbed. In a modular build, the modules are scheduled onto a truck and a crane on a specific day. If the slab is not cured or the access is not ready, the delivery is rescheduled — and the crane is not free.

Second, the site half becomes a larger proportion of the total. When the building itself is faster and more predictable, the site works stop being a rounding error and become the main source of variance in the final invoice.

Delivery day §

Modules arrive on trucks and are placed by crane. Published modular guidance reports crane hire at approximately A$260 to $1,530 per hour with four to ten hour minimums plus travel, and notes that remote or complex lifts can push delivery-day totals to roughly A$23,000 to $30,600.^[5]

The variables are access rather than distance alone: whether a semi-trailer can reach the block, whether the crane has standing room and a clear lift path, whether overhead powerlines or street trees interfere, and whether traffic control or escort vehicles are required.^[5] These are questions to resolve before a contract is signed, because they cannot be resolved cheaply afterwards. See delivery, transport and craneage for the full picture of install day.

Connecting services §

Published modular guidance reports electricity, water, sewer and telecommunications connections at approximately A$7,600 to $30,600 depending on location, and notes that rural blocks commonly require a septic system at A$15,300 to $38,200.^[5]

Where a block sits relative to existing infrastructure matters more than any other variable here. New estates frequently have services stubbed to the boundary; established infill blocks may require substantially more work, and one guide singles out sewer connections requiring a private pump-out as a common example.^[3] Connection charges are set by the relevant utility and vary by state and by network, so no single national figure applies. Published national figures for these charges are not covered by the sources compiled here — get written quotes from the relevant water authority and electricity distributor for your address.

Council and certifier charges §

Statutory and professional charges sit outside the construction contract entirely. One 2026 guide groups them as development application or complying development certificate fees, infrastructure contributions, energy assessments, the occupation certificate and surveyor fees, and reports inner Sydney councils charging over A$25,000 in contributions on a single dwelling.^[3]

Contribution rates are set locally. In NSW they are levied under section 7.11 of the Environmental Planning and Assessment Act and calculated under each council's own contributions plan, and they can apply to secondary dwellings as well as new houses.^[11][12] Because the rates differ by council and change over time, the council's published contributions plan is the only reliable figure for a given address; no national or state average is given here.

Where a prefabricated, manufactured or transportable dwelling is used in NSW, Part 3 of the Local Government (Manufactured Home Estates, Caravan Parks, Camping Grounds and Moveable Dwellings) Regulation 2005 applies alongside the planning approval — a separate instrument that a construction quote will not cover.^[12]

Reading a quote §

The recurring theme across published guidance is that these items are quoted separately and are, in the words of one guide, almost never included in builder contracts.^[3] These questions are worth asking of any quote before signing:

1. Has a soil investigation been done on this block, and what class did it return? If not, the site-works figure is an assumption, not a quote.^[1]
2. Is the site-works figure a fixed price or a provisional sum? A provisional sum is an estimate that will be reconciled against actual cost — and the buyer typically pays the difference if the assumption was wrong.
3. What exactly is in the site-works line, and what is explicitly excluded?
4. What radius does delivery cover? Transport and installation are sometimes included only within a set distance of the factory.^[5]
5. Who arranges and pays for the crane, and what happens if the lift takes longer than the quoted hours?^[5]
6. Who pays council contributions, and have they been quoted for this specific address?^[3]
7. What contingency should be held? Published guidance suggests 10% on a flat-block new build, 15% on a sloping site and 20% on a knockdown rebuild.^[3]

What is not covered here §

There is no published independent survey of Australian site-works costs. Every figure on this page comes from a builder, a trade or a commercial cost-guide publisher, each of which has a commercial position. Where sources conflict, both ends are shown above rather than reconciled.

State-specific service connection charges, council contribution rates and on-site wastewater approval requirements are not covered by the sources compiled here and vary too widely to summarise. The relevant utility and the local council are the sources for those.

Related guides §

• Delivery, transport and craneage — the other half of the on-site cost.
• Foundations for modular and prefab homes — slab, stumps, piers and screw piles compared.
• What "turnkey" actually includes
• Gardens and outdoor space with a modular home — trees, decks, retaining walls and landscaping.
• How much does a modular home cost in Australia?
• Glossary — site classification, provisional sums, prime cost items.

References §