DBB means design–bid–build; DB means design–build. In Australian construction, DB is commonly called design and construct (D&C). The main difference is who holds the design appointment and when the builder becomes responsible for the design.
| Question | Design–bid–build | Design–build / D&C |
|---|---|---|
| Who appoints the designers? | Usually the client | Usually the contractor, sometimes after a transfer of an existing design team |
| When is the builder appointed? | After the client develops design and tenders the build | While the contractor still has design to develop or complete |
| How many main appointments? | Separate design and construction contracts | One main design and construction contract |
| Where is client design control? | More direct through the client’s designers | Defined through the brief, requirements and agreed review process |
When might DBB suit the client?
It can suit a project where the owner needs close design control and can spend the time to develop and coordinate detailed documentation before tender. The contractor prices the described works. The client still needs to manage design quality and information interfaces, and changes after contract award can affect time and cost.
When might D&C suit the client?
It can suit a project whose performance and quality can be stated clearly, especially where contractor design input and overlapping design and construction offer value. The contractor coordinates its designers with delivery. The owner must be able to assess whether tender proposals and subsequent design meet the brief.
Is one always faster or cheaper?
No. Procurement time, tender competition, design maturity, risk allocation and later changes affect the result. A fast D&C tender with an incomplete brief can leave expensive decisions for later. A well-documented DBB project can price clearly, but it takes time to reach tender. Government guidance sets out benefits and risks for both approaches rather than declaring a universal winner.
Choose the route by the project’s design needs, client capability, programme and risk profile. Then make the brief, documentation and contract match that choice. Read the D&C definition or how a design and build project proceeds.
Sources and further reading
- Office of the Victorian Government Architect — procurement of buildings
- NSW Government — construction procurement contract systems
Related guides
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