This week our staff chatted about the concept of delegated design and what it is, when it happens, and who is in charge of it.
What is Delegated Design?
Delegated Design generally means transferring certain aspects of design responsibilities from Architects (A) to General Contractors (GC). It relates to the ‘means and methods’ of construction which may go beyond an architect’s ability to design a non-proprietary building system or give the contractor some flexibility in how a system is constructed. Also, the Designer (Architect or Engineer) may want to push the cost of the design of a building system (i.e. metal stairs and railings) off to the contractor to keep design fees reduced.
Is the Architect still responsible for the design of the delegated design system?
Although certain aspects of the delegated design system are the responsibility of the Contractor, system design oversight remains with the Architect in that the delegated design system will likely have design requirements that are in addition to the Contractor’s design responsibility to fit into the “big picture” of a building and meet the Owner’s project goals. Overall code compliance of the system is also the responsibility of the Architect and it is incumbent on the Architect to confirm that the delegated design component or system meet the requirements of the code by confirming that the delegated design submittals meet or exceed specified code compliance goals.
How does it relate to Architectural drawings?
Usually the architect will identify items to be constructed utilizing a delegated design process in the specification.
A building system defined by performance specification is defined by specific design criteria that gives the contractor some flexibility to meet the system requirements. There may be several ways to achieve the requirements of a performance specification utilizing means and methods of construction. Delegated design is a requirement of performance specification used when the contractor is required to engineer a system to meet building code compliance and an engineer’s certification is required. The appearance of the system may be included in the Drawings, however, the structural aspects of the assembly require engineering that may be beyond the design control of the Designer due to the varying manufactured components of an assembly with different manufacturer’s products.
Items are identified on the drawings using keynotes that direct the contractor to the specification. The GC provides shop drawings showing the delegated system design and is stamped by a Massachusetts registered engineer and/or accompanied by stamped engineering structural calculations for the Architect and Design Team to review. The Architect’s review of the shop drawings primarily deals with the aesthetic and general compliance with the design intent but also is required to ensure that the delegated system design meets specified code provisions. If the Architect finds that the delegated design meets specified design criteria, the Architect approves the shop drawings for the GC to use for construction.
Examples of delegated design:
- Curtain Wall Systems – The curtain wall construction often depends on the curtain wall manufacturer’s system capabilities or means of reinforcing the CW framing system which are specific to each individual manufacturer’s system. The system should be designed to meet the architect’s vision of mullion thickness, mullion pattern, glass position in the frame and CW opening conditions. The architect will provide the design criteria (wind load, seismic load, etc. factors that the delegated design engineer will use to determine the structural resistance capabilities for the curtain wall system and an anchoring method to attach the CW to the surrounding building construction based on the characteristics of the selected curtain wall manufacturer’s system.
- Metal Panel Systems – Similar to the curtain wall system…
- Accessory parts of connection to structure and MEP system – Often supports for a heavy pipe, duct or even rooftop HVAC equipment will require the contractors to design the supports, dunnage, hangers, etc. This is again based on the needs of the contractor’s equipment manufacturer requirements (weight, dimensions, equipment point load locations, duct inlet/outlet locations, etc.) for their specific equipment.
- Elevator / Escalator – The elevator manufacturers have different designs for the elevator car guiderails, brackets, machine room equipment. The contractor’s selected elevator supplier will design the guiderail/bracket system and related design loads to integrate into the surrounding building construction.
- Metal stairs, handrails and guardrails – Although our structural engineer could design these systems, typically we have the contractor’s metal fabrications contractor provide a delegated design for these components to save design costs. The metal stair and rail system is most times located in a stair tower that the architect may not need a high level design appearance so will leave the assembly of the stair up to the contractor. The architect will provide basic stair dimensions and a handrail/guardrail design. The contractor will have some flexibility in how the stair is fabricated but the specifications will require the contractor to fabricate the stair and railings to meet code required load requirements.
Delegated design vs. early consultant engagement
Acquiring constructability information early in the design phase through consultants can be very helpful, but sometimes it depends on availability and expertise of the consultants. Manufacturers of a system may be willing to contribute design information early on in the process to inform the integration of these systems in the project design. Collecting this additional information from “experts” helps the Architect better understand the delegated design system, its requirements and limitations that impact the adjacent building components. Depending on the project type, we may not have leverage on public projects to entice manufacturers to participate in early design of a delegated design system, likely because the information required is not yet available or they are unwilling to design something for a project that might be supplied by another competitor (public projects require 3 manufacturers of any given product or system).