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Who carries the design responsibility?
Foundation Series · Episode 8 of 12
Tina Patel & Bart Kolosowski · 19 February 2026
A contract should do more than record a price. It should make responsibilities and the process clear.
Bart and Tina compare traditional, design-and-build and contractor-designed portions, then explore what homeowners need to understand about the agreement behind their build.
A red brick is not the same as the red brick you had in mind
Bart uses a simple specification example: asking for a red brick is different from naming a particular product. The level of detail matters when a contractor is responsible for developing parts of the design.
Under a design-and-build arrangement, the requirements need to explain what matters to you while identifying where the contractor has room to choose the solution. That freedom can support delivery, but it can also change how much control you retain.
The useful question is which choices must be fixed and which may be developed by the builder. Discuss that with the team before you compare proposals or assume the finished specification is already agreed.
01
Choose the route
Agree the delivery arrangement.
02
Define the design
Allocate each package clearly.
03
Set requirements
Record the outcome you expect.
04
Agree the process
Understand payments and change.
Design-and-build passes on work; it does not make the work disappear
The route can bring design and delivery under the contractor’s organisation. That still requires people with the skills to develop information, coordinate specialists and manage the process.
Tina and Bart describe why a capable traditional builder may not have the same experience or resources for design-and-build. The contractor needs to be suited to the responsibility being proposed.
They also discuss what happens when the existing design team moves to work for the contractor. Clarify who employs whom, how decisions will be communicated and what support remains on your side.
Who designs the glazing, staircase or joinery?
An architect may set the appearance and intent of a staircase or glazing package, while the specialist supplier develops the detailed solution used to manufacture it.
Contractor-designed portions can make that division explicit within an otherwise traditional arrangement. The scope still needs to identify the intended result and how the specialist design will be coordinated with the rest of the home.
Do not leave the responsibility between two appointments. Ask who develops the detail, who checks its interfaces and when it needs to be ready for the programme.
Understand how the agreement works before construction starts
A headline price and a signature do not explain every part of a construction agreement. The design documents, specification and agreed procedures also matter to the way the project is delivered.
The hosts recommend clarity about scope, payment, change, timing and defects. Different standard forms and project arrangements use different roles and processes; the choice should suit the job and the people administering it.
Ask your adviser to explain the agreement and any proposed amendments before you commit. Everyone should understand how instructions and decisions will be recorded while the work is under way.
Three decisions to take into your project
01 Choose responsibilities before the form.
Discuss the procurement route while planning how the design will be developed.
02 Make important requirements explicit.
Identify the specifications and choices you need the agreement to preserve.
03 Understand the administration.
Agree who gives instructions and how payment, changes and defects will be handled.
The full conversation
The Foundation Series is our 12-episode guide to the home project journey. Architect Tina Patel and quantity surveyor Bart Kolosowski work through the decisions, people and processes involved, step by step.
In Episode 8, Bart and Tina explain procurement routes, the division of design responsibility and why a well-understood construction agreement supports a smoother project.
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