It’s one of the most common conversations in commercial management. The job has been held up for weeks waiting on design from the principal. Everyone on site knows why. The emails go back and forth, the programme slips, and somewhere in the middle of all that, the 28 days to lodge an extension of time claim quietly runs out. Then the letter arrives about liquidated damages.

So is the claim dead? Sometimes. Not always. And the answer usually sits in one clause most people never read closely.

What AS 4000 actually requires

Under the unamended AS 4000, clause 34 runs on two separate tracks:

  • Clause 34.2: either party must promptly give written notice of anything that will probably cause delay, with the cause and an estimate.
  • Clause 34.3: the contractor is entitled to an extension of time only if it lodges a written claim within 28 days of when it should reasonably have become aware of the cause, evidencing the facts of causation and the extent of the delay.

The clock starts when you should reasonably have known, not when the delay ends and not when you finally get around to the paperwork.

Then clause 34.5 puts the superintendent on a clock too. They have 28 days to assess your claim, and if they don’t, the extension is deemed granted as claimed. The same clause gives the superintendent a power to extend time at any time before the final certificate, whether or not the contractor has claimed or is entitled (UTS ePress).

That last sentence is the reserve power, and it matters more than most people realise.

Why a missed time bar isn’t always the end

In Peninsula Balmain Pty Ltd v Abigroup Contractors Pty Ltd [2002] NSWCA 211, decided under AS 2124’s equivalent clause, the contractor had not claimed its extensions properly. The NSW Court of Appeal held that the superintendent’s reserve power can be used for either party, and that the superintendent must act honestly and impartially in deciding whether to use it (Construction Law Made Easy).

On those facts, a fair superintendent would have extended time for delays the principal caused. The date for practical completion moved and liquidated damages came down (Bradbury Legal). The NSW Court of Appeal followed the same reasoning in Probuild v DDI Group [2017] NSWCA 151 (i-law).

Put simply, a principal that delayed the job can’t always sit behind your missed deadline and collect liquidated damages for its own delay.

Why you shouldn’t rely on it

That’s the good news. Here’s why I wouldn’t build a commercial strategy on it.

  1. The court left room to refuse. If a claim comes in so late that the facts are hard to verify, that can be a fair reason for the superintendent to refuse (Construction Law Made Easy). The longer you wait, the weaker your position.
  2. Principals have rewritten the clause. Amended contracts often describe the reserve power as an “absolute discretion”, “for the sole benefit of the principal” or “no obligation to exercise”. In one Growthbuilt case, the court refused to imply a duty of good faith where the power was expressed as an absolute discretion for the principal’s benefit (CMS).
  3. Without the reserve power, you’re arguing contested law. In Gaymark v Walter Construction (NT, 1999), the reserve power had been deleted, the contractor missed its notices, and the court still found time “at large”. It is a first-instance decision, widely criticised and rejected in England (Storia), and Turner v Austotel in NSW went the other way (FEG). That is not an argument you want your margin riding on.

What to check when you’ve missed it

  1. Clause 34.3 as amended. Is the claim period a condition precedent? Has it been shortened or changed to business days?
  2. Clause 34.5 as amended. Is the reserve power unamended, rewritten as an absolute discretion, or deleted? This decides how much room you have.
  3. The deemed grant. Has the 28-day deemed approval survived the amendments?
  4. Ask now, with evidence. If the reserve power is still there, write to the superintendent asking them to use it, with the instruction or request records and an impacted programme. Speed matters.
  5. Get advice if the amounts are significant. The outcome depends on your exact wording.

The better answer: don’t need the rescue

The reserve power is a fallback. The real protection is never missing the window in the first place.

Most missed time bars don’t happen because people don’t know the rule. They happen because the instruction or the hold point was never captured properly when it happened, so nobody started the clock. For the variation side of the same problem, see time bar clauses in Australian construction contracts.

That’s the problem Varipack is built for. Site crews capture instructions by voice and photo when they happen. The original field timestamp is kept even if the phone syncs later. Each project carries its own contract-specific notice settings, so the notice and time-bar checks run against your contract, not a generic 28 days. The original evidence stays as the primary record.

Varipack doesn’t decide entitlement for you, and it doesn’t replace commercial judgement. Not every instruction is a valid variation or a qualifying delay. What it does is make sure the clock gets started and the evidence exists while you still have time to act. See how Varipack works →

If you’re a subcontractor who has felt that sinking feeling of finding the window has already closed, I’d like to hear how it happened.

This article is general information, not legal advice. Your rights depend on the exact terms of your contract and the facts. Get specific advice before relying on any of this.

Sources and further reading