These are different procurement routes, not a rule that builders must always be contacted last. [1]
Use early conversations for the right purpose
At an initial meeting, ask about comparable work, availability, access to the site and what information is needed to prepare a quotation. Label any early budget discussion as provisional. Do not ask different builders to price different verbal descriptions and then compare the totals as though they cover the same work.
Give the same brief to the designer and prospective contractors. Keep one list of decisions still to be made: layouts, structural openings, finishes, equipment and what work is excluded.
Understand the two main routes
Separate designer and builder
In a traditional route, the design team is normally appointed first, with sufficient design information prepared before competitive tendering. Contractors then price a common scope. RICS warns that tendering from incomplete information reduces certainty about cost and time. [1]
Design & build
A design-and-build arrangement combines design and construction responsibilities under the chosen contractual structure. It does not remove the need to define the client's requirements or the design work included. Ask who appoints the engineer, who coordinates revisions and who checks that the construction information is complete. [1]
Planning drawings are not the whole construction package
Building regulations approval is separate from planning permission. An approved planning scheme does not, by itself, establish compliant construction details. [2]
For structural work, agree whether the engineer's service includes calculations, drawings, specification and site advice. The engineer's design dimensions should not be treated as fabrication dimensions for ordering steelwork without the contractor's checks. [3]
Questions to settle before accepting a price
Ask each bidder to identify the drawing revisions used, assumptions, exclusions and any work priced only as an allowance. Request separate treatment of items you will buy yourself. Then ask what happens to the price when a still-open decision is resolved.
The aim is not to eliminate every uncertainty before a conversation with a builder. It is to avoid confusing an early estimate with an agreed price for a sufficiently defined job.
Decide who coordinates the project
The building regulations dutyholder arrangements require cooperation between designers and contractors. On a domestic project, identify the people controlling the design and construction phases and clarify the principal designer and principal contractor arrangements. A company label alone does not allocate every responsibility. [4]
Before authorising work, keep the design scope, construction scope and responsibilities together in one project record. Treat unanswered coordination questions as matters to resolve, not as services you assume someone else has included.