Traditional roles for deferred design performed by the constructor
Describing the contractor’s design obligations is not a new or unique concept. Design professionals have deferred aspects of design responsibility to contractors as long as there have been architects, engineers, and contractors. Deferring design works best when final design of specific elements is resolved as a component of construction deliverables, rather than a detailed portion of the construction document set.
The constructor has traditionally been responsible for design solutions associated with constructability (means and methods). There are cost benefits to the project when deferred design components form a part of the constructor’s solution that fits within their responsibilities for means and methods through effective scheduling and elimination of potential rework. For example, the RPR may provide the engineering information associated with connections between steel members or accumulated building load paths required for design of foundation components (piles, piers, and similar structures), while the constructor provides shop drawings containing the final design solutions. These solutions are prepared by a supporting registered professional to meet building code requirements for design responsibility, but the supporting registered professional does not take responsibility for the engineering of those components (which remains with the RPR).
The increasing complexity of construction through the latter half of the 20th century means it is becoming more common for design components to be described as forming a part of the constructor’s design contribution. This includes design of building elements not strictly associated with engineered outcomes of construction methodology. These components are typically pre-engineered (i.e. not requiring site-specific engineering) or require specialist contributions RPRs do not have within their knowledge base or experience.
There is increasing responsibility for building envelope and fire-protective solutions, conveying systems, and other pre-engineered elements forming a part of the deferred or collaborative design assigned or delegated as part of the contractor’s project deliverables. These form the basis for discussion in this practice guide.
Avoid deferred engineering
Deferred design is not intended to defer engineering. The RPR is fully responsible for indicating required performance and engineering within the documents provided to the constructor. As indicated in Part 1 of this series, the concept of ‘design’ versus ‘engineering’ is critical in communicating what responsibility is being deferred to the constructor.
One example of inappropriate deferred engineering could occur if a structural engineer unintentionally omits critical annotations fully describing the size of steel members and the loads and eccentricities associated with connections between them. The final delegated design requirement from the constructor is the connection solutions provided by the steel fabricator based on the engineering information within the documents supplied by the structural engineer.
If information is omitted, the steel fabricator may become responsible for confirmation of the sizes of the steel members. However, this should not be the fabricator’s responsibility unless clear direction for that component is also provided through identification of any engineering requirement in the specification documents.
Engineering (building code compliance) cannot be delegated. However, many professional design practices have inadvertently delegated engineering through the improper application of notes on drawings indicating a delegated design requirement without or with incomplete engineering direction, causing professional responsibility to the project to be questioned by contractors. Often, the ‘delegated design’ annotation is written on a drawing set by a well-meaning technologist that did not confer with the RPR. The RPR responsible for that component of engineering is the only person who can direct the need for delegated design.