If there’s one thing years of experience have taught me as a construction lawyer in Brisbane, it’s that most disputes don’t come from major legal battles; they start with small, preventable contract mistakes. A missed clause here, a vague scope of work there, and before you know it, both parties are locked in a costly dispute that drains time, money, and trust.

Whether you’re a homeowner, builder, subcontractor, or developer, understanding what can go wrong in your Construction Agreements isn’t just good practice; it’s essential protection. Contracts are the backbone of every project, and yet, too often, they’re treated as formalities rather than the working documents they need to be.

Let’s walk through the most common contract mistakes I see every week in Brisbane’s construction scene, the legal principles behind them, and how you can avoid falling into the same traps.

Why Construction Contract Mistakes Matter

The Australian construction industry is one of the largest and most complex sectors of the economy, generating billions of dollars annually. According to the Australian Bureau of Statistics, it consistently ranks among the top contributors to GDP and employs hundreds of thousands across the nation. With that level of activity comes risk, and legal disputes are a significant part of it.

Studies consistently show that ambiguous contract terms, incomplete documentation, and poor variation procedures are leading causes of disputes in construction projects. Research published in the Journal of Legal Affairs and Dispute Resolution in Engineering and Construction found that over 60% of construction disputes stem from unclear or incomplete contract terms. It’s not that people intend to cut corners, it’s often that they don’t know what’s missing until it’s too late.

Here in Queensland, laws like the Building Industry Fairness (Security of Payment) Act 2017 and the Queensland Building and Construction Commission Act 1991 (QBCC Act) set clear standards for what contracts must include, and how payments and variations should be managed. When contracts fail to comply, they not only expose you to disputes, but they can also be legally unenforceable.

The 10 Most Common Contract Mistakes (and How to Avoid Them)

1. Vague or Incomplete Scope of Works

The problem: The contract simply says “renovate kitchen” or “supply and install roofing” without detailed drawings, material specs, or performance standards.

Why it matters: Ambiguity invites disagreement. Without specifics, both parties might have completely different expectations of what “completion” looks like.

The fix: Attach detailed scope documents, drawings, specifications, and a list of inclusions and exclusions. Include clear completion criteria and a sign-off procedure. Under QBCC guidance, the scope must be “sufficiently detailed” to avoid uncertainty, vague descriptions can invalidate parts of the agreement.

2. Poorly Defined Payment Terms

The problem: Phrases like “payment on completion” or “as agreed” appear instead of a structured payment schedule.

Why it matters: Cash flow is critical in construction. Without clear milestones, disputes arise over when payments are due or whether they’re justified.

The fix: Use a detailed payment schedule with milestones, due dates, and retention terms. The Building Industry Fairness (Security of Payment) Act mandates specific timelines for progress payments and claims. If your contract conflicts with the Act, statutory rights override it, meaning you might lose control over how payments are managed.

3. No Formal Variation Process

The problem: Changes are agreed verbally on-site, with no paperwork.

Why it matters: Variations are the leading cause of cost blowouts and disputes. Without written confirmation, one party may deny ever agreeing to the change, or dispute its cost.

The fix: Require all variations to be in writing, signed by both parties, and to include cost and time implications. Even urgent on-site decisions should be followed up in writing within 24–48 hours.

4. Unbalanced Risk Allocation and Insurance Gaps

The problem: One party takes on all risks, often through broad indemnity clauses or missing insurance details.

Why it matters: Overreaching indemnities can be unenforceable or financially devastating. In small business contracts, they may even breach Australian Consumer Law provisions on unfair terms.

The fix: Limit indemnities to what’s reasonable, and confirm that insurance policies (public liability, contract works, professional indemnity) align with the project’s risks. Always request certificates of currency before work begins.

5. Missing or Weak Dispute Resolution Clause

The problem: The contract jumps straight to court proceedings without requiring negotiation or mediation.

Why it matters: Litigation is slow and expensive. Without a structured process, even minor disagreements can spiral into lawsuits.

The fix: Insert a “dispute resolution ladder”, negotiation, then mediation, then arbitration or litigation as a last resort. Courts often favor parties who attempt alternative dispute resolution (ADR) before filing proceedings.

6. Non-Compliance with Statutory Requirements

The problem: Contracts missing mandatory details like QBCC licence numbers, statutory warranties, or cooling-off rights.

Why it matters: Non-compliant contracts can be unenforceable and expose you to penalties. The QBCC Act outlines strict content requirements for residential building contracts, including written form, party details, and statutory terms.

The fix: Use QBCC-compliant contract templates or have your lawyer cross-check your agreement against statutory requirements before signing.

7. Unrealistic Project Timelines and Liquidated Damages

The problem: Deadlines that don’t consider weather delays, supply chain issues, or council approvals.

Why it matters: Unrealistic timeframes make liquidated damages disputes inevitable.

The fix: Base timelines on practical schedules and include a fair mechanism for extensions. Ensure liquidated damages are reasonable and proportionate, or they risk being considered a penalty, and therefore unenforceable.

8. Ambiguous Completion and Defects Liability Terms

The problem: No clear definition of “practical completion” or defects liability period.

Why it matters: Parties disagree on whether the project is finished and when final payments or retentions are due.

The fix: Define practical completion, include a defects checklist, and specify the defects liability period (typically 12 months). Link final payments to formal completion certification.

9. Overuse of Boilerplate Templates

The problem: Copy-pasting a contract from a previous job or an online template.

Why it matters: No two projects are identical. A template might omit key risk provisions relevant to your project.

The fix: Treat templates as a starting point, not a final product. Have a qualified lawyer review and tailor it to your project’s scope, procurement method, and risk profile.

10. Poor Record-Keeping and Notice Procedures

The problem: Notices and claims are sent informally via text or verbal updates.

Why it matters: Many legal rights (like extensions of time or delay claims) depend on timely, valid notices.

The fix: Follow the contract’s notice requirements to the letter, use the correct address, method, and timeframe. Keep daily site records, photos, and written confirmation of instructions.

Lessons from Research and Law

A 2020 study by Campos-Gutierrez et al. on construction disputes found that ambiguity in contract documentation, poorly managed variations, and payment delays accounted for the majority of conflicts. The research aligns with Queensland’s own dispute trends, where the QBCC reports that documentation failures and scope disputes consistently lead their complaint statistics.

Under the Security of Payment legislation, strict notice periods and payment schedules exist to protect contractors’ cash flow. Yet, non-compliance remains widespread, often because the underlying contracts are unclear.

In short, the law gives parties tools to prevent disputes, but contracts must use them correctly.

A Practical Checklist Before You Sign

Here’s what I always check when reviewing a Construction Agreement:

Clear identification of all parties and licence numbers (if applicable)
Detailed scope of works with drawings and specifications
Payment schedule compliant with the Security of Payment laws
Formal written variation process
Fair indemnity and insurance provisions
Realistic program and extension of time clauses
Step-by-step dispute resolution procedure
Statutory compliance with QBCC and BIF Act
Defined completion and defect processes
Notice requirements that match your project’s communication practices

If your contract ticks these boxes, you’re already ahead of most disputes I see.

Why Early Legal Advice Matters

Too often, clients come to me after the problem has already occurred, a payment withheld, a variation denied, a schedule blown out. By then, options are limited.

Engaging construction lawyers Brisbane early, before signing, allows you to negotiate better terms, ensure statutory compliance, and avoid hidden traps. Legal advice at the start costs a fraction of what disputes cost at the end.

Avoiding Disputes Before They Begin

Construction contracts don’t have to be minefields. With careful drafting, clarity, and compliance, they become powerful tools that protect both parties and keep projects on track. Most disputes I see could have been avoided with a clear scope, a fair payment schedule, and proper variation documentation.

If you’re about to sign a contract or already managing one that feels unclear, take the time to get it reviewed. A well-drafted Construction Agreement is more than a legal formality, it’s your blueprint for a smooth, dispute-free project.

And if you’re unsure where to start, reach out. The best time to talk to a lawyer isn’t when the problem hits, it’s before it ever has a chance to begin.