The short answer: the biggest red flags in a residential building contract are vague or excessive Provisional Sums and Prime Cost items, broad escalation and variation clauses that let the builder pass through costs you didn't intend to accept, weak warranty terms or missing HBC insurance details, ambiguous start dates and timeline penalties, and any clause that limits the builder's defect liability below the NSW statutory minimum.
A custom home contract is dense. Most homeowners read the cover page and the price, then sign. The clauses that actually matter — and that account for almost every dispute we see between builders and clients — sit in the middle of the document, often in language that looks routine.
Here are the patterns worth pushing back on before you sign.
Red flag 1 — PS and PC items that hide the real cost
The pattern: the contract sum looks competitive, but inside it are 15–25 Provisional Sums (PS) and Prime Cost (PC) items, each for thousands of dollars, none specified.
Why it matters: PS allowances move based on actual cost. PC items move based on what you actually choose. A contract with $80,000 in open PS/PC lines isn't a $1.2M build — it's a $1.2M-plus-whatever build.
What to push back on:
- Ask why each PS exists and whether it can be replaced with a fixed line by doing more work upfront (site investigation, selections)
- Compare PS/PC totals across competing quotes — they should be similar if the site was investigated to the same depth
- For each PC item, ask for the allowance amount and the typical actual cost. If "allowance $1,000 / typical $3,500" — you're being underquoted
Red flag 2 — Soft escalation and rise-and-fall clauses
The pattern: language allowing the builder to increase the contract sum based on "increases in material costs," "labour rates," "market conditions," or similar.
Why it matters: in a genuine fixed-price contract, the builder carries the cost-rise risk. Escalation clauses transfer that risk back to the homeowner. After the 2021–2023 cost inflation cycle, these clauses became more common — and more aggressive in scope.
What to push back on:
- Strike out broad escalation language entirely if you're paying for fixed-price
- If escalation has to stay, cap it at a specific percentage and tie it to a published index (e.g. ABS Producer Price Index for construction)
- Confirm the rise-and-fall clause has a corresponding fall-clause (if material prices drop, your contract sum drops). Most don't — that's the giveaway
Red flag 3 — Variation clauses with broad pass-through rights
The pattern: clauses that let the builder issue variations for "unforeseen site conditions," "regulatory changes," or "matters outside the builder's control" — with little definition.
Why it matters: variations on big-ticket items (foundations, drainage, retaining walls) can be tens of thousands of dollars. Broad language gives the builder unilateral discretion to pass these costs through.
What to push back on:
- Require that any variation includes a written description, cost, and homeowner approval before work proceeds
- For the "unforeseen site conditions" clause specifically: ask whether the site has been investigated. A properly geotechnically-investigated site has very few genuine surprises
- Cap variation administration fees — some contracts charge a flat fee per variation just to process it
Red flag 4 — Weak or missing warranty/HBC details
The pattern: the warranty section is vague, doesn't reference the Home Building Act 1989, or doesn't include HBC certificate details.
Why it matters: the statutory warranty applies regardless of what the contract says, but a contract that doesn't reference it clearly suggests the builder isn't comfortable with the law. The HBC certificate is mandatory for any residential build over $20,000 — its absence is a serious problem.
What to push back on:
- Confirm the contract references NSW Home Building Act 1989 statutory warranties
- Confirm the HBC certificate number is in the contract or appended
- Ask for any extended warranty in writing with specific terms (what's covered, what voids it, claim process)
- See our explainer on NSW builder warranties
Red flag 5 — Vague start date and timeline language
The pattern: "construction will commence following council approval" or "completion within a reasonable timeframe."
Why it matters: without firm dates, the builder isn't on the hook for delays. You can be paying rent for 6 months past your expected handover with no contractual recourse.
What to push back on:
- Tie the start date to a specific milestone with a cap (e.g. "construction to commence within 4 weeks of CC issue, no later than [date]")
- Confirm a written construction program is appended to or referenced in the contract
- Confirm what happens if the builder misses the practical completion date — most NSW contracts include a liquidated damages clause (small daily penalty) but it varies
Red flag 6 — Payment schedules front-loaded against milestones
The pattern: the payment schedule asks for 30–40% on slab pour, with no corresponding deliverable.
Why it matters: payment schedules in NSW residential contracts must be roughly tied to actual progress. Front-loading payments creates cashflow risk — if the builder fails, you've paid more than you've received.
What to push back on:
- Compare the payment schedule against the construction stages — payments should be roughly proportionate to work completed
- The Home Building Act limits deposits to 10% of contract price for work over $20,000 (5% if over $7,500). A builder asking for more is breaching the Act
- For progress payments, the Act requires they be claimable only after the relevant stage of work is completed
Red flag 7 — Limitation of liability clauses
The pattern: clauses limiting the builder's total liability, excluding consequential damages, or attempting to disclaim certain defects.
Why it matters: in NSW, the statutory warranties cannot be contracted out of. But limitation clauses can affect non-statutory damages — and complicate disputes if something goes wrong.
What to push back on:
- Have the limitation clause reviewed by a building lawyer specifically — these vary widely in enforceability
- Strike out any clause that attempts to limit liability for personal injury, fraud, or wilful misconduct
- Strike out any clause that conflicts with the statutory warranties under the Home Building Act
Red flag 8 — Dispute resolution that favours the builder
The pattern: clauses requiring arbitration in a specific venue, with named arbitrators, or that preclude going to NCAT (NSW Civil and Administrative Tribunal).
Why it matters: NCAT is the standard dispute forum for NSW building contracts and is faster and cheaper than private arbitration. A clause preventing NCAT recourse limits your options.
What to push back on:
- Confirm the dispute resolution clause allows NCAT proceedings for matters under the Tribunal's jurisdiction
- If private arbitration is offered, confirm the arbitrator is jointly nominated (not unilaterally chosen by the builder)
- The right to escalate to a court for matters of law should be preserved
Red flag 9 — Variations to specifications late in the contract
The pattern: a specification document that's incomplete or refers to "or equivalent" on key items, with no clear approval mechanism for what "equivalent" means.
Why it matters: "Or equivalent" gives the builder discretion to substitute cheaper materials or fixtures with no homeowner review. Quality can degrade significantly through these substitutions.
What to push back on:
- Specifications should name brands and models for major items (appliances, tapware, tiles, joinery hardware, windows)
- "Or equivalent" should require homeowner written approval before substitution
- The specification document should be appended to the contract as a numbered schedule
Red flag 10 — Anything verbal that's not in the contract
The pattern: during sales conversations, the builder commits to inclusions, finishes, or timelines that don't appear in the written contract.
Why it matters: unwritten promises don't bind. If it's not in the contract, it's not happening — regardless of what was discussed.
What to push back on:
- Every verbal commitment goes into the contract as a written term
- Email confirmations of conversations are useful but not a substitute for contract amendments
- If the builder resists writing something down, take that as data
The questions to ask before signing
- Is the contract a NSW-standard building contract (HIA, Master Builders, or equivalent)? Custom contracts deserve more scrutiny than standard templates.
- Has the contract been reviewed by my building lawyer or solicitor? A 1-hour review is cheap relative to the contract value.
- Have I seen the full specification, with no "or equivalent" on key items?
- Is the HBC certificate appended or referenced by number?
- Are PS and PC items minimised, with each one explained?
If a builder resists any of these questions or any of the pushback above — that's the most important data of all.
How we write our contracts
We use NSW-standard residential building contracts. We have very few Provisional Sums and Prime Cost items because we do the site investigation and selection work upfront. We don't carry rise-and-fall clauses. The HBC certificate is provided before deposit. The specification is appended in detail.
If you're at the contract-comparison stage and want a second pair of eyes — particularly on the PS/PC structure or on escalation clauses you're not sure about — get in touch. Even if Macan isn't the builder you ultimately choose, an hour of help reading a contract pays back many times.
Important caveat: this is general information about residential building contracts in NSW, not legal advice. Have any contract reviewed by a building lawyer or solicitor specialising in construction matters before signing. Building law changes — check the current text at the NSW Fair Trading website.
