Design and construct puts one contractor in charge of design and construction under a single contract. AS 4902 is the standard form most Sydney commercial projects use for this delivery method. A developer’s own architect can be novated to the contractor once the contract is signed.

Single point accountability shifts fitness for purpose risk onto the contractor, not the client. Design and construct suits projects where design certainty and program speed matter more than direct control over each design decision.

What One Contract Means Under AS 4902

AS 4902 is the standard contract form behind Sydney design and construct projects. The standard sets out what single point accountability commits a contractor to.

AS 4902-2000 is the most widely used design and construct contract in Australia. The standard sits within the same suite of conditions as AS 4000, the general construction contract form.

Single point accountability removes the handoff between separate architects and builders that traditional tendering carries. One contractor answers for both design and construction outcomes under this contract.

The Principal’s Project Requirements Set the Starting Brief

The client provides Principal’s Project Requirements at contract signing. These cover preliminary drawings, specifications and performance criteria the finished building must meet.

The contractor develops the design from this brief through to construction. Design decisions after signing sit with the contractor, within the requirements set at the start.

Novation Moves Your Design Team to the Contractor

A developer’s own architect or consultant can be novated to the contractor once the contract is signed. Novation means the same design team continues the project, now working for the contractor instead of the client.

Novation preserves design intent while shifting contractual responsibility. The client keeps continuity of design without holding the design risk directly.

Why Developers Choose Single Point Accountability

Single point accountability removes the coordination gap between separate design and construction contracts.

One Contractor Carries Design and Build Risk Together

A single contractor answers for both design and construction outcomes under this model. Traditional tendering splits that responsibility across a separate architect and a separate builder.

Risk concentration is the entire commercial logic behind design and construct. The client trades direct design control for a single point of contact and a single point of liability.

Overlapping Design and Construction Compresses the Program

Construction can begin on early packages while later design elements are still being finalised. Traditional tendering does not allow this overlap, since construction only starts once design and documentation are complete.

Program compression is one of the clearest commercial advantages of this model. Projects with a fixed completion deadline benefit most from this structure.

Design and Construct vs Construction Management: Which Risk Sits Where

Design and construct concentrates design and build risk in one contractor, while construction management spreads delivery across separately managed trade packages.

Design and construct suits projects where the client wants one accountable party for the finished outcome. Construction management suits projects where the client wants visibility and control over each individual trade package.

Neither model outperforms the other in isolation. The right choice depends on how much design certainty exists at the outset and how much direct oversight the client wants to retain. Our breakdown of construction management in Sydney sets out how that alternative structure works.

Where Design and Construct Risk Sits

Fitness for Purpose Is the Contractor’s Obligation

AS 4902 places fitness for purpose obligations on the contractor, not the client. The finished building must perform as the Principal’s Project Requirements describe, and the contractor carries that obligation.

Construct only contracts place design risk with the client’s own consultants instead. Design and construct shifts that risk onto the contractor, who prices it into the contract sum accordingly.

Variations and Extensions of Time Decide Who Pays for Change

Variations and extension of time provisions determine how scope changes are priced and who absorbs delay. These clauses receive the heaviest negotiation of any part in a design and construct contract.

Clear variation terms at signing prevent disputes once construction starts. Our builder evaluation checklist covers why undefined variation terms cause the most common cost overrun on commercial projects.

When Design and Construct Is the Wrong Model

Design and construct is not the right model when a client needs direct control over individual design decisions throughout the build.

Clients who want to select finishes, materials and design details progressively lose that flexibility once a design and construct contract is signed. Design authority sits with the contractor within the agreed requirements, not with the client on an ongoing basis.

Projects with an incomplete or evolving brief carry more risk under this model. Ambiguity in the Principal’s Project Requirements at signing becomes a variation claim later.

Director-Led Accountability on Every Design and Construct Program

Director-led oversight keeps design and construction accountability in one place through every stage of a design and construct program.

Single point accountability only works when that accountability sits with someone consistently involved from signing through to handover. Our director-led delivery approach keeps senior oversight in place across the full program, not only at contract execution.

Frequently Asked Questions

What is a design and construct contract? 

A design and construct contract makes one contractor responsible for both design and construction under a single agreement. AS 4902 is the standard form for this in Australia.

Who owns design risk under a design and construct contract? 

The contractor carries fitness for purpose obligations under AS 4902. The finished building must meet the Principal’s Project Requirements set at contract signing.

Can a client keep their own architect under a design and construct contract? 

Yes, through novation. The client’s architect or consultant transitions to work for the contractor once the contract is signed, continuing the same design intent under new contractual terms.

Key Takeaways: Choosing Design and Construct for Program Certainty

Single point accountability trades direct design control for one contractor answering for design and construction together.

Tau Constructions delivers design and construct projects under AS 4902 with director-led oversight from signing through to handover. Our design and construct service outlines how we structure this accountability across a Sydney build.