Sub-Consultant
A specialized design professional, such as a structural, mechanical, or electrical engineer, retained by the project's architect rather than directly by the owner or general contractor, forming a design team under the architect's own contract with the owner.
Why it matters
Who hires whom in a design-build-contract chain actually matters for liability: a structural engineer working as the architect's sub-consultant is generally answerable to the architect, not directly to the contractor, which shapes how a design dispute gets resolved if something in that engineer's design goes wrong.
On a real project
An architect retains a structural engineer as a sub-consultant under the architect's own contract with the owner, rather than the owner or general contractor hiring the structural engineer directly, which is the typical arrangement on a design-bid-build project.
Who this matters most to
A Structural Engineer is frequently retained as a sub-consultant to the architect rather than contracted directly by the owner, which shapes the reporting and liability relationships on the project.
Where this goes wrong
A contractor assumes it can go directly to a structural engineer to resolve a design question, not realizing the engineer is a sub-consultant to the architect and contractually answers to them instead. The contractor's request gets rerouted through the architect, adding delay that could have been avoided by understanding the actual contractual chain from the start.