AS4000 vs AS2124: comparing Australia's two dominant construction contracts

Two contracts, one industry standard

AS4000-1997 and AS2124-1992 are the two most widely used Standards Australia general conditions of contract for lump-sum construction work in this country. Both are drafted for a construct-only delivery model — the principal engages a consultant to design, then contracts a builder to build. Both use a superintendent to administer the contract. Both are recognisable to anyone who works in construction procurement.

The similarities end at the structure. AS2124 is a 1992 form that reflects an older, principal-friendly risk allocation. AS4000 is the 1997 update — same DNA, but recalibrated after years of criticism about contractor exposure. Choosing between them (or amending either) is a substantive commercial decision, not a stylistic one.

AS2124-1992 in short

• Vintage. First published 1992, superseding AS2124-1986. Still used widely by state government principals and older public infrastructure agencies.
• Risk skew. Broader principal-favouring provisions on latent conditions, delay damages and variations.
• Time bars. Extension-of-time notices are relatively short and strict.
• Superintendent. Acts partly as agent of the principal and partly as an independent certifier — a duality that continues to generate disputes.

AS4000-1997 in short

• Vintage. Published 1997 as a general revision of AS2124, drafted by a Standards Australia committee representing principals, contractors and consultants.
• Risk skew. More balanced. Latent conditions carry a defined framework, and time-bar language is tighter but the trigger points are clearer.
• Payment. Modernised progress claim, progress certificate and final claim regime — designed to operate alongside state Security of Payment legislation.
• Superintendent. Same dual role, but with clearer obligations to act honestly and with impartiality in its certifying function.

Where the two diverge in practice

Latent conditions

AS2124 excludes liability for latent conditions unless notice is given promptly and specific requirements are met. AS4000 has similar mechanics but a clearer definition of what qualifies as a latent condition and how the additional cost or time is measured.

Variations

Both forms allow the superintendent to direct variations. AS4000 is more prescriptive about pricing methodology and the contractor's right to be paid where a direction is later disputed as being within scope.

Extensions of time

AS2124's EOT provisions are shorter and the case law on strict compliance is well-developed. AS4000 broadens the categories of qualifying delay events and gives the superintendent a discretion to grant an EOT even where the contractor has failed to give notice — a "prevention principle" safety valve that AS2124 lacks.

Liquidated damages

Both cap LDs at the rate stated in the annexure. AS4000 is clearer that LDs are the principal's sole remedy for delay unless the annexure says otherwise.

Dispute resolution

AS2124 provides for arbitration by default. AS4000 introduced a tiered process: senior executive negotiation, then expert determination or arbitration by election. Neither displaces a party's right to bring adjudication under the applicable Security of Payment legislation.

Which one should you use?

For most private commercial construction work in Australia, AS4000 is now the default starting point. It reflects the current commercial expectations of both principals and contractors, and it plays cleanly with the statutory payment regime.

AS2124 is still appropriate where a principal (particularly a government principal) has a longstanding suite of amendments drafted against it, or where the risk allocation the principal wants is closer to the older form. It is also common on large civil infrastructure work where the parties want the historical certainty of AS2124's well-tested wording.

For design and construct projects, use AS4300-1995 — not AS4000. For minor works, AS4906-2005 or AS4902-2000 (D&C) may be more appropriate.

Common amendments to watch for

• Time bar tightening. Reducing the EOT notice window to 5 or 7 days, and making the notice a condition precedent to any entitlement.
• Cap on liability. Introducing an aggregate liability cap (often a percentage of the contract sum) with carve-outs for personal injury, IP infringement and wilful misconduct.
• Consequential loss exclusion. Excluding indirect and consequential loss but defining what is included in "direct loss" — the drafting here decides who wears delay damages beyond the LD rate.
• Superintendent replacement. Reserving a broader right for the principal to replace the superintendent, sometimes with a nominated firm rather than an individual.
• Security. Increasing the retention or bank guarantee amount and extending the release timing to reflect defects liability plus a tail.

Getting it right

Whether the base form is AS4000 or AS2124, the commercial outcome is set by the annexure and special conditions. A "standard" AS4000 with a 40-page annexure is not a standard contract. Envision Legal reviews and negotiates AS4000, AS2124 and AS4300 contracts for principals, head contractors and subcontractors across Australia.

This article contains general information only and does not constitute legal advice. Envision Legal accepts no liability for any loss arising from reliance on this content. You should seek independent legal advice tailored to your specific circumstances.