The short answer
| Construction drawings | Shop drawings | |
|---|---|---|
| Prepared by | Architect and engineers (design team) | Contractor, subcontractor, fabricator or their detailer |
| Purpose | Show design intent; basis for permit, pricing and contract | Show how a specific item will be made and installed |
| Scope | Whole project, all disciplines | One trade or component (steel, millwork, glazing, duct…) |
| Detail | Enough to define the design | Every dimension, connection, material and fixing |
| Approval | Permit authority | Design team review before fabrication |
Why shop drawings exist
Design drawings deliberately leave fabrication decisions to the trades: the exact connection a steel fabricator uses, how a cabinet maker builds a carcass, which extrusions a glazing system uses. Shop drawings fill that gap. They let the design team confirm the trade has understood the design – and let the trade fabricate with confidence.
The submittal and approval process
- The subcontractor or fabricator prepares shop drawings from the contract documents and field dimensions.
- The general contractor reviews them for coordination and submits them to the architect or engineer.
- The design team reviews for conformance with the design intent and returns them marked, for example 'approved', 'approved as noted' or 'revise and resubmit'.
- The trade revises if needed, then fabricates from the approved drawings.
Who is responsible for what?
Responsibility is set by the contract, but in general the design team remains responsible for the design and the contractor for dimensions, quantities, fabrication methods and coordination between trades. A design team's review of shop drawings normally does not relieve the contractor of responsibility for errors in them. In the US, documents such as AIA A201 describe this split; other countries have their own standard contract forms.
Common types of shop drawings
- Structural steel, rebar and precast
- Millwork and joinery
- Glazing, curtain wall and storefront
- HVAC ductwork, plumbing and electrical coordination drawings – see MEP coordination
Tips for faster approvals
- Follow the specification section numbers in your submittal.
- Cloud every change on resubmissions.
- Raise RFIs early instead of guessing in the drawings.
- Show field dimensions clearly as verified or to be verified.
Our shop drawing services prepare submittals for every major trade.
In short: construction drawings say what to build; shop drawings prove the trade knows exactly how it will build it.
Keeping track of submittals
A simple submittal log – item, specification section, date submitted, reviewer, status and date returned – keeps everyone honest about where each package stands, and shows early which approvals threaten the fabrication schedule.
Digital shop drawings and BIM
Many trades now produce shop drawings from 3D fabrication models – Tekla for steel and precast, Revit fabrication parts for ductwork and pipework, specialist software for millwork and glazing. The model also produces CNC data and quantities, and can be checked against the design model for clashes before submittal. The approval process stays the same, but errors are found much earlier.
Examples of the difference
A structural drawing might show a steel beam as W12x26 with a moment connection at each end and a note referring to the connection design. The steel shop drawing shows that same beam with its exact cut length, every hole position and diameter, the end plates with their dimensions and welds, the piece mark used on site, and the camber if any. Similarly, an architect's interior elevation shows a reception desk's size, materials and finishes; the millwork shop drawing shows every panel, joint, hardware item and fixing.
Who pays for shop drawings?
Shop drawings are part of the trade's scope and are usually included in the subcontract price. Many fabricators outsource them to specialist detailing firms, which is why shop drawing services are a large part of the drafting industry. Delays caused by poor shop drawings usually fall on the trade, which is another reason to use experienced detailers for critical packages.
What a good shop drawing includes
- Project name, specification section and submittal number.
- Plans, elevations and sections at a readable scale, keyed to the contract drawings.
- Every dimension needed for fabrication, with field-verified dimensions marked.
- Materials, grades, finishes and product references.
- Connection and fixing details to the building structure.
- Clouded changes and a revision block on resubmissions.
Submittals, product data and samples
Shop drawings are one kind of submittal. Others include product data (manufacturer's sheets showing the selected product meets the specification), samples (physical finishes and materials) and mock-ups. Specifications normally list which submittals each trade must provide. Missing or late submittals are one of the most common causes of schedule delays on site.
Coordination drawings: the step in between
On complex projects, especially with heavy MEP, trades prepare coordination drawings before or alongside shop drawings. These combine the work of several trades in one drawing or model, so conflicts are resolved before each trade finalises its own shop drawings. Today most coordination happens in BIM, with combined services drawings issued from the coordinated model.
How long shop drawing review takes
Contracts usually give the design team a set review period – often around two weeks per submittal, sometimes less for simple items. Plan the submittal schedule backwards from fabrication lead times, and submit early for long-lead items such as structural steel, curtain wall and switchgear. A rejected submittal restarts the clock, which is why complete, accurate shop drawings save so much time.
