AS4300-1995 is the General Conditions of Contract for Design and Construct published by Standards Australia. It is one of the most widely used construction contracts in Australia for commercial, civil and government Design and Construct projects. Rachelle Hare advises Contractors, Principals and subcontractors on AS4300 across Queensland and Australia.
AS4300-1995 is the Australian Standard General Conditions of Contract for Design and Construct, published by Standards Australia in 1995. A 2024 University of Melbourne study found it remains one of the most frequently used construction contracts in Australia, particularly for commercial and civil D&C projects.
The fundamental difference between AS4300 and the construct-only forms (AS4000 and AS2124) is design responsibility. Under AS4300, the Contractor takes responsibility for the design as well as construction. The principal provides either a design brief, a preliminary design or a design that is then novated to the Contractor. From that point, design liability sits with the Contractor.
This design responsibility carries significant commercial consequences. It affects professional indemnity insurance requirements, defects liability exposure, scope boundary management, and how variations are assessed when the Contractor's design differs from what was expected. Understanding these consequences before signing is what a thorough AS4300 review addresses.
AS4300 is administered by a Superintendent, who occupies a dual role: acting as the Principal's agent in some functions and as an independent certifier in others. The Superintendent's powers under AS4300 are substantial and their decisions can significantly affect payment, time and cost outcomes on a project.
AS4300 covers three different Design and Construct arrangements. Which variant applies determines how design responsibility is shared between the Principal and the Contractor.
The principal provides a design brief setting out the project requirements. The contractor develops the design from the brief and constructs the works. The contractor carries full design responsibility from the brief forward. This is the most commonly used AS4300 arrangement and places the greatest design liability on the Contractor.
The principal provides a Preliminary Design, usually developed to a defined percentage of completion. The contractor takes that design, completes it and constructs the works. The contractor is responsible for the completed design. Where the preliminary design contains errors or inadequacies, the scope of the Contractor's design responsibility and the extent of any cost sharing is often a source of dispute.
The principal engages a designer during the tender phase, then novates the designer's appointment to the Contractor after award. The contractor takes on the designer's obligations and becomes responsible for the design. The interaction between the original designer's work and the Contractor's design liability requires careful management, particularly for professional indemnity insurance.
AS4300 is 30 years old. Since it was published, significant legislative changes have occurred in Australia that the contract does not address. Many Principals issue it with heavily amended Special Conditions. Understanding both the base document and the amendments is essential before any AS4300 Design and Construct Contract is signed.
Clause 42 governs progress payment claims, the Superintendent's assessment process, and when payment is due. It interacts with Queensland's Building Industry Fairness Act 2017 in ways the base document does not contemplate. The payment timeframes in the contract cannot exceed the maximums set by BIFA for building work. Understanding how Clause 42 and BIFA operate together matters for every Queensland AS4300 project.
AS4300's variation mechanism covers changes to the Scope of Works and the Principal's Project Requirements. Variations must generally be directed in writing by the Superintendent. The interaction between the Principal's design brief, the Contractor's developed design, and what constitutes a variation is one of the most commonly disputed issues under AS4300. Tight variation notice requirements can extinguish entitlements to additional payment if not managed actively.
AS4300 requires the Contractor to give written notice of a claim for an extension of time within a specified period after the delay event. The contractual notice timeframe and the consequences of failing to serve notice in time are critical. Special Conditions frequently shorten the notice period below the standard form default. Missing the notice requirement can extinguish an EOT claim regardless of whether the delay was caused by the Principal.
Clause 12 sets out the Contractor's design obligations and the warranties they give about fitness for purpose and compliance with the Principal's Project Requirements. These obligations are broader than in a construct-only contract. The interaction between design warranties under AS4300 and the Contractor's professional indemnity insurance requires specific attention, particularly in design novate and construct arrangements where the novated designer's original work is involved.
AS4300 provides for termination by the Principal for default and convenience, and termination by the Contractor for principal default. The convenience termination provisions entitle the Contractor to costs and a reasonable profit on work done, but the assessment and payment process involves the Superintendent and is subject to dispute. Special Conditions frequently modify termination provisions in ways that affect what the Contractor can recover.
AS4300 was published in 1995, before the GST, the Personal Property Securities Act, the harmonised WHS legislation and proportionate liability reforms came into effect. These matters are not addressed in the base document and must be covered by Special Conditions. Contracts that go out without adequate Special Conditions on these issues leave both parties with uncertainty on how significant legal frameworks interact with the contract terms.
AS4300 is almost never used unamended. Principals issue it with Special Conditions that modify the standard risk allocation. Most amendments shift risk onto the Contractor. Understanding what the Special Conditions have done to the standard form is the central task of any AS4300 Design and Construct Contract review.
Common areas of amendment include liability caps and indemnity provisions, payment timeframes and retention mechanics, EOT notice requirements and delay damage rates, design responsibility boundaries, termination payment entitlements, and dispute resolution provisions.
Rachelle has reviewed and negotiated AS4300 Design and Construct Contracts in her in-house roles at Thiess, Laing O'Rourke and Acciona, and in private practice at Corrs Chambers Westgarth and McCullough Robertson. She has advised on AS4300 projects across Queensland, New South Wales and the ACT, including commercial buildings, civil infrastructure, government projects and defence facilities.
Get your AS4300 Design and Construct Contract reviewed →AS4300 and AS4000 are the two most widely used Australian standard form head contracts. Choosing between them comes down to who carries the design. If the Principal provides the complete design and the Contractor builds it, AS4000 is the appropriate form. If the Contractor takes on design responsibility, AS4300 is the appropriate form.
Contractor carries design responsibility from the Principal's Project Requirements. Design warranties apply. Professional indemnity insurance requirements are specific to design. Superintendent administers. Lump sum. Novation of consultants possible. Design liability exposure extends beyond construction defects to fitness for purpose.
Principal provides and retains the design. Contractor builds to the design. No design responsibility on the Contractor except for temporary works. Superintendent administers. Lump sum or schedule of rates. AS4000:2025 is the updated version released in June 2025 with PPSA, WHS and dispute resolution changes. Core risk allocation unchanged from 1997.
Rachelle Hare has reviewed, drafted and negotiated AS4300 Design and Construct Contracts throughout her 25+ year career. As Acting General Counsel at Thiess, she managed AS4300 engagements from inside a major contractor. In private practice at Corrs Chambers Westgarth and McCullough Robertson, she advised Principals and Contractors across Queensland and New South Wales on AS4300 procurement and disputes.
She has worked on AS4300 projects across commercial construction, civil infrastructure, government and defence. That breadth means she understands how both Principals and Contractors use this contract in practice, and where the disputes most commonly arise.
At Blaze Business & Legal, she provides fixed-price AS4300 Design and Construct Contract reviews, Special Conditions analysis, and advice on AS4300 issues on live projects. Fixed-price quote before work begins.
Rachelle Hare has reviewed and negotiated AS4300 Design and Construct Contracts across Queensland and Australia throughout her 25+ year career. Fixed-price quote before any work begins.
Fixed-price reviews. Fast turnaround available. Statements of Departures if required.
