HIA contracts: the full suite explained

TL;DR

HIA publishes the most widely used residential building contract suite in Australia. Fixed-price new home contracts are the workhorse for most residential jobs; cost-plus is available but restricted by state legislation (in VIC, work must be $1M+ or the scope genuinely can’t be priced at signing). Every state has its own HIA edition aligned to local legislation. Access via HIA Contracts Online (credit-based, members pay roughly half of non-member rates). If you’re choosing between fixed price and cost-plus, fixed price protects your margin on a well-scoped job; cost-plus protects the client on unknowable scope, but only where the law allows it.

What the HIA contract suite covers

The Housing Industry Association publishes residential building contracts for all Australian states and territories. The suite covers:

New home construction (lump sum / fixed price)
Alterations, additions and renovations
Cost-plus (where permitted by state law)
Small works (below the state’s written contract threshold)
Kitchen, bathroom and laundry supply and install
Swimming pool and landscaping (QLD)
Commercial works (small and medium, with or without architect)
Subcontractor and trade contracts (project and period)
Supporting documents (variation forms, progress claim certificates, EOT notices, preliminary agreements)

All HIA residential contracts are drafted by lawyers and updated automatically when state legislation changes — a key reason builders and certifiers accept them readily.

Contracts Online: how access works

HIA delivers all contracts through Contracts Online, a web-based platform (verified 2026-05-09). Key mechanics:

Feature	Detail
Delivery model	Credit-based. Buy credits, spend them to produce contracts.
Minimum credits	2 credits per contract (builder copy + owner copy). Extra copies cost more.
Member pricing	HIA members pay roughly half of non-member rates per contract.
Non-member access	Available via guest account; higher per-contract cost.
Legislative updates	Automatic when state legislation changes. No manual version tracking.
Multiple logins	Staff can have separate logins under one account.
Storage	Contracts stored online; download and print as needed.

For specific credit and subscription pricing, contact HIA at 1300 650 620 or log into the Contracts Online platform.

State editions at a glance

Each state’s contracts are tailored to local legislation. The contract name and scope differ by jurisdiction.

New South Wales

Legislation: Home Building Act 1989 (NSW) (verified 2026-05-09).

Written contract mandatory for residential work over $5,000 (verified 2026-05-09, NSW Government).

Contract	Use when
NSW Residential Building Contract for New Dwellings	New home construction or taking over incomplete works requiring substantial completion
NSW Residential Building Contract for Renovations and Additions	Alterations, additions, modifications to existing structures
NSW Residential Building Contract for Works on a Cost Plus Basis	Scope is genuinely unknowable at contract signing
NSW Residential Building Contract for Small Works over $20,000	Non-complex residential projects $20,000+ that don’t require a full new home contract
NSW Residential Building Contract for Small Works between $5,000 and $20,000	Projects under $20,000 (cabinets, carports, garages, pergolas); below HBCF insurance threshold
NSW Kitchen, Bathroom and Laundry Supply and Install Contract	Supply-and-install work limited to these room types
NSW Medium Works Commercial Contract	Small to medium commercial work
NSW Project Trade Contract	Builder-to-subcontractor for a single trade package
NSW Period Trade Contract	Ongoing subcontractor relationship across multiple jobs

Deposit cap: 10% for all NSW residential contracts (verified 2026-05-09, NSW Government).

Victoria

Legislation: Domestic Building Contracts Act 1995 (VIC).

Contract	Use when
VIC New Homes Contract	New home construction
VIC Alterations, Additions and Renovations Contract	Existing structure modifications
VIC Cost Plus Contract	Work $1M+ OR renovation/restoration where scope can’t be priced at signing (verified 2026-05-09, HIA)

The VIC cost-plus restriction is stricter than other states: you cannot use cost-plus simply because you prefer it. Non-compliance means the contract may not be enforceable without a VCAT order.

Queensland

Legislation: Queensland Building and Construction Commission Act 1991 (QLD).

Contract	Use when
QC1 New Home Construction Contract	Standard new home; allows provisional sums and unforeseen circumstance clauses
QC2 Peace of Mind New Homes Construction Contract	New home; builder knows site conditions fully; no provisional sums or unforeseen clauses
QC3 Alteration, Addition and Renovation Contract	Renovations, additions, partial construction phases
QLD Domestic Construction Cost-Plus Contract	Scope genuinely cannot be priced even excluding provisional sums
QLD Small Works Contract	Domestic work under $20,000 not affecting foundations
QLD Kitchen, Bathroom and Laundry Supply and Install Contract	Supply-and-install KBL work, off-site fabrication involved
QLD Swimming Pool and Landscaping Contract	Pool and landscaping scope
QLD Minor Works Contract	Work under $3,300 or small commercial projects

QC1 vs QC2: QC1 is the safer default for most builders. QC2 locks out variations via provisional sums, so use it only when the scope and site are fully known before signing.

Western Australia

Legislation: Home Building Contracts Act 1991 (WA) (full text) governs residential building work between $7,500 and $500,000 (verified 2026-05-09, HIA WA submission 2025).

Contract	Use when
HBCA Lump Sum Building Contract (Form 6A)	Residential new homes and major renovations under HBCA
WA Alterations and Additions Contract (Form 38E)	Alterations and additions over $7,500 and under $500,000
WA Pre-fabricated Homes Contract (Form 45C)	Modular or transportable home construction
WA Small Works Contract	Domestic work $7,500 or under (HBCA does not apply)

South Australia

Legislation: Building Work Contractors Act 1995 (SA).

HIA publishes an SA Standard Building Contract for New Homes and an SA Small Works contract (for domestic alterations and renovations up to $30,000) (verified 2026-05-09, HIA product listing).

Fixed price vs cost-plus: the core decision

See the dedicated articles for full treatment: HIA fixed price contracts and HIA cost-plus contracts.

The short version:

Factor	Fixed price	Cost-plus
Scope clarity	Required: complete drawings and specs	Works for unknowable scope
Cost risk	Builder carries overruns	Client carries cost; builder takes fee
Builder’s fee	Margin built into contract sum	Explicit fee (set amount or % of cost, default 20% if unspecified)
Legislative restriction	Available in all states	Restricted in VIC (must be $1M+ or renovation with unknowable scope)
Client exposure	Predictable budget	Open-ended; estimate required at signing
Variation risk	High if PC/PS items present	Lower: actuals are paid

Cost-plus requires a written fair estimate at contract signing. That estimate is not the price; it is the builder’s best calculation at the time. Miscommunicated estimates can attract Australian Consumer Law liability, so document your reasoning.

Default builder’s fee on HIA cost-plus: if you elect a percentage rather than a fixed fee, the HIA contract defaults to 20% of the cost of building works if no percentage is stated (verified 2026-05-09, HIA cost-plus guidelines).

Member vs non-member access

HIA Contracts Online is available to both HIA members and non-members. Members pay significantly less per contract (verified 2026-05-09, HIA Contracts Online). If you regularly produce more than a handful of residential contracts per year, HIA membership typically pays for itself on the contract cost savings alone, independent of other member benefits (legal helpline, contract advice, training).

For current membership and contract credit pricing: hia.com.au/signup or call 1300 650 620.

Trade and subcontractor contracts

The HIA suite includes two trade contract formats:

Contract	Use when
Project Trade Contract	Single-project subcontractor scope (plumbing package, electrical package, etc.)
Period Trade Contract	Ongoing relationship across multiple jobs. Pair with Work Orders for each individual job.

Both specify scope, payment terms, defects liability, and insurance requirements for the subcontractor. Using these instead of a handshake or unsigned quote is the single biggest risk-reduction step a residential builder can take with subbies.

What can go wrong

Wrong contract for the job. Using a small works contract for a $300,000 renovation that hits the new homes threshold. The wrong form may not satisfy state legislation mandatory requirements and creates insurance gaps.
Cost-plus in VIC without meeting the threshold. In VIC, a cost-plus contract used for a $700,000 renovation is technically non-compliant under the Domestic Building Contracts Act 1995 (VIC). Enforcement risk falls on the builder.
QC2 in QLD when site conditions are uncertain. QC2 excludes unforeseen circumstance clauses. Discovering an unexpected slab condition mid-build with no provisional sum mechanism is a dispute waiting to happen.
Not updating to the current edition. HIA contracts update when legislation changes. Contracts Online handles this automatically for digital contracts. If you are using old paper packs, check whether the edition is still current before signing.
Filling in the builder’s fee field incorrectly on cost-plus. If the percentage field is left blank, the default 20% applies. Verify the fee structure is correctly stated in the schedule before countersigning.
Missing or incomplete schedules. PC sums, PS items, site details, insurance details. An unsigned or incomplete schedule is a blank cheque for disputes at reconciliation.

References

HIA Contracts Online (Housing Industry Association) (verified 2026-05-09)
NSW Building Contracts and Related Documents (HIA) (verified 2026-05-09)
QLD Building Contracts and Related Documents (HIA) (verified 2026-05-09)
Which building contract should you use in Victoria? (HIA) (verified 2026-05-09)
Guidelines when using cost plus contracts (HIA) (verified 2026-05-09)
Guide to providing home building contracts (NSW Government) (verified 2026-05-09)
HIA Submission: Review of Western Australia’s home building contract laws (HIA, September 2025) (verified 2026-05-09)
Home Building Act 1989 (NSW) (verified 2026-05-09)