Design first or design and build? Deciding who should own the remaining design decisions

When a business commissions a new building, a fit-out, a production line or a piece of special-purpose equipment, it faces an early choice that shapes the whole project. One path is to have the design completed first, by your own team or an independent designer, then ask contractors or suppliers to build exactly what has been designed. The other is to describe what you need and ask a single contractor or supplier to both design and deliver it.

In construction these are often called traditional (or construct-only) delivery and design and construct (or design and build). In equipment and manufacturing projects the equivalent choice is between build-to-print, where the supplier makes what your drawings show, and design-and-supply or turnkey arrangements, where the supplier designs to your requirements. The labels matter less than the underlying question: who should own the design decisions that remain open when you go to market?

Getting that answer wrong is a common source of disputes, cost overruns and disappointing results. This article explains the trade-offs, the misunderstandings that cause trouble and a practical way to decide.

Design is rarely finished when you go to market

Very few projects reach procurement with every design decision made. Some decisions stay open because specialist suppliers know more than the client, because technology choices are still evolving or because detailed integration is best done by whoever will build the result. The real choice is how much design to complete before engaging the market, and who will complete the rest.

In traditional delivery, the client controls design before construction. The client, through its designer, makes most design decisions and carries more responsibility for whether the design works.
In design and construct, the contractor turns the client’s requirements into an integrated design and delivers it. More design responsibility, and more design risk, transfers to the contractor.

Each approach creates its own risks.

The trade-offs

Factor	Traditional (design first)	Design and construct
Client control over design	High	Lower once the contract is let
Price comparison between tenders	Easier, because everyone prices the same design	Harder, because each tenderer proposes its own design
Single point of responsibility	No: designer and builder are separate	Yes: one party designs and builds
Interface risk between design and construction	Higher	Lower
Use of contractor or supplier expertise	Limited	Greater
Time to start construction	Often longer	Often shorter, as design and construction can overlap
Client’s need for a clear performance brief	Important	Essential
Client’s internal design capability needed	High	Still important, to define and check

Neither approach is automatically better. The right choice depends on how mature the design is, how capable the client is, how much expertise the market has and how much the client needs to control the result.

Five common misunderstandings

“Design and construct transfers all design risk.” It transfers some. The client still carries risk for its own brief, information it provides, approvals it controls and changes it makes.
“Traditional delivery gives maximum certainty because the design is complete.” A complete design can still contain errors, gaps and coordination problems, and in a traditional model those usually remain the client’s responsibility.
“We can issue detailed drawings and still make the contractor responsible for performance.” If you prescribe the solution in detail, the contractor has little freedom to achieve the performance, and responsibility becomes blurred.
“We can keep approval rights over every design decision without affecting risk.” Extensive approval rights can amount to controlling the design, which can shift responsibility back towards you and slow the project.
“Choose the model that is fastest.” Schedule matters, but it should not be the only factor.

Match authority with accountability

The guiding principle is to align design authority with design accountability:

If you want to control the detailed design, accept that you retain more of the risk that comes with it.
If you want the contractor or supplier to be responsible for performance, give it enough freedom to make the design decisions needed to achieve that performance.

The strongest arrangements align five things: technical freedom, approval authority, professional responsibility, acceptance testing and change control. When they point in different directions, disputes follow.

Five tests for choosing the model

1. Design maturity

How much of the design already exists? If you have a proven standard design used before, a traditional or build-to-print approach may preserve that standard and allow competitive pricing. If you are starting from a concept, design and construct may make better use of market expertise.

2. Internal capability

Can you, or an independent designer working for you, manage the design and check its quality? If not, carrying design responsibility yourself is risky.

3. Market expertise

Do contractors or suppliers know more about the solution than you do? For specialised technology, such as automation systems, refrigeration or process equipment, specialist suppliers often design better solutions than a general designer.

4. Integration

Would separating design from construction create significant interface risk? Complex systems with many interdependent parts often benefit from a single responsible party.

5. Control

How much detailed design authority do you genuinely need? Standardisation across sites, brand requirements or specific operational needs may justify keeping more control.

Defining the outcome is always your job

Transferring design responsibility does not remove your obligation to define what you need. A design-and-construct contract with a vague brief invites tenders that solve different problems, are hard to compare and lead to disputes about what was promised.

A good performance brief covers:

Function: what the result must do.
Performance: measurable requirements such as capacity, speed, temperature, accuracy, energy use or noise.
Constraints: site conditions, standards, safety and environmental requirements, budget and schedule.
Interfaces: how the result connects with existing buildings, equipment, utilities, systems and people.
Acceptance tests: how you will verify that the result meets requirements.
Non-negotiables: requirements that must not be traded away.

Even when you outsource design, keep enough technical capability, internally or through an independent adviser, to act as an intelligent client: someone who can understand, question and check the design. Never outsource your ability to judge whether a design is fit for purpose.

A worked example

This is an illustration. A small food manufacturer needs a new packing room with a conveyor, a checkweigher, a labeller and a cold room. It has two options.

Option 1: design first. The owner engages an independent engineer to design the layout, specify each item of equipment and prepare drawings. Three suppliers quote to supply and install the specified equipment, and a builder quotes for the room. The tenders are easy to compare, but the owner is responsible for making sure the separately supplied equipment works together. During commissioning, the checkweigher’s reject mechanism does not suit the conveyor speed, and the labeller’s control system will not talk to the checkweigher. Each supplier says its equipment meets the specification. The owner pays for modifications.

Option 2: design and supply. The owner writes a performance brief: pack 40 cartons a minute, weigh and reject underweight cartons, label each carton with product and batch information, hold the room at a specified temperature, fit within the existing building and meet food safety and electrical requirements. Two integrators propose complete solutions. Comparing them takes more effort, because the designs differ, so the owner hires the independent engineer for a few days to evaluate them. The chosen integrator is responsible for the whole line meeting the brief, demonstrated through agreed acceptance tests.

For this owner, with limited internal engineering capability and a system whose parts must work closely together, the second option suits better. A business with a proven standard packing line used at several sites, and strong in-house engineering, might reasonably choose the first.

Hybrid approaches

The choice is not always all or nothing. Common hybrids include:

Design to a point, then hand over. The client’s designer develops the concept and key decisions, and the contractor completes the detailed design. In construction, the client’s designer is sometimes transferred to the contractor to finish the design, an arrangement often called novation.
Specialist design within a traditional project. The main design is completed by the client’s designer, but specialist systems, such as refrigeration, automation or fire services, are designed and supplied by specialist subcontractors to performance requirements.
Early contractor involvement. A contractor or supplier is engaged early, sometimes under a separate agreement, to advise on buildability, cost and programme before the main contract is let.
Standard design with local adaptation. A proven standard design is supplied to the contractor, who adapts it for site-specific conditions and takes responsibility for those adaptations.

Hybrids can capture the benefits of both approaches, but they need especially clear statements of who is responsible for which design decisions and where the boundaries sit.

Governance after the contract is signed

Whatever model you choose, decide in advance:

Who can approve design changes, and how quickly.
What your approvals mean. Distinguish between reviewing a design to check it meets your brief (assurance) and directing how it should be done (control). Directing the design tends to take back responsibility.
Who verifies the design, provides constructability or manufacturability feedback and conducts final acceptance.
How changes in your requirements are handled, priced and documented.

Long approval cycles can become a schedule bottleneck and blur accountability. Keep reviews focused on whether the design meets the brief.

Signals worth watching

A design-and-construct contract accompanied by highly prescriptive drawings.
A traditional contract with major design interfaces still unresolved.
Repeated approval cycles that delay work and blur who is responsible.
Variations caused by gaps between the designer’s and the builder’s scopes.
Suppliers each claiming their part meets the specification while the system as a whole does not work.

How this applies to a small Australian business

Small businesses often commission projects infrequently and may lack in-house design expertise. Practical guidance:

For simple, well-understood work, such as a standard shed or a straightforward fit-out, a clear design first and competitive quotes often work well.
For specialised or integrated systems, such as automation, refrigeration, process equipment or complex services, design-and-supply from a capable specialist can reduce interface risk.
Invest in a good brief. A few days of an independent engineer’s time to write requirements and acceptance tests is usually well spent.
Keep an intelligent client on your side to evaluate proposals and check designs.
Read the contract carefully, especially design responsibility, approvals, variations, acceptance and warranties, and get advice on significant contracts.
Check licensing and approvals: some design and building work must be done or certified by licensed or registered practitioners, depending on the state and type of work.

The article on how much design you need before seeking quotes covers the related question of timing.

Questions to put to contractors and suppliers

When evaluating design-and-construct or design-and-supply offers, ask each tenderer:

How does your proposed design meet each performance requirement, and what margin does it leave?
Which parts of the design will you complete after award, and when will we see them?
Which assumptions about our site, existing equipment or operations does your design rely on?
Who in your team is responsible for the design, and what qualifications or registrations do they hold?
How will you demonstrate that the completed work meets the acceptance tests?
What happens if a test fails, and how quickly will you fix it?

Their answers reveal whether the tenderer genuinely understands your requirement and is prepared to own the design. Compare the answers side by side, and treat vague or evasive responses about design responsibility as a warning, however attractive the price. A slightly more expensive tenderer who clearly owns the design and the acceptance tests is often the lower-risk choice over the life of the project.

Common mistakes

Choosing a delivery model by habit rather than by the project’s characteristics.
Writing a vague brief for a design-and-construct contract.
Prescribing detailed solutions while expecting the contractor to guarantee performance.
Keeping approval rights that amount to design control while trying to transfer design risk.
Losing the ability to judge the design after outsourcing it.
Ignoring interfaces between separately procured items.
Selecting on schedule alone.

Questions to ask

Which design decisions remain open, and who is best placed to make them?
Does our design authority match the responsibility we expect to keep or transfer?
Is our performance brief clear enough to support design freedom?
What technical capability must we keep to act as an intelligent client?
Which interfaces become simpler or harder under each model?
What will our approvals mean, and how will we keep them from slowing the project?
How will we test that the result meets our requirements?

Bringing it together

The choice between designing first and asking a contractor to design and build is really a choice about who owns the remaining design decisions. Traditional delivery keeps control with you, along with more of the risk. Design and construct transfers more design responsibility, but only works with a clear performance brief and enough freedom for the contractor to meet it. Decide based on design maturity, your own capability, market expertise, integration complexity and the control you genuinely need. Whichever model you choose, define the outcome clearly, keep an intelligent client on your side, and make sure design authority and design accountability point the same way.

Source: KEVOS notes. Examples in this article are illustrations. This article is general information, not legal advice.