Why do steel fabricators prepare the beam when the structural engineer has already prepared the same beam? Because the two drawings provide different information. Where construction drawings are compared to shop drawings, construction drawings show what is required to be built. Shop drawings show how the work done by the particular trade is to be done.
Construction drawings are done by the architect and engineers, represent the design, and constitute the contract. Shop drawings are done by the contractor, subcontractor, or fabricator in order to demonstrate the way that a particular part of the job is to be fabricated and erected. Under the terms of AIA A201, the shop drawings are not contract drawings and the architect will check them for compliance with the design.
What Are Construction Drawings?
Construction drawings are the design team’s set. Together with the specifications, they make up the contract documents, which is what makes them binding. A typical commercial set includes:
- Architectural sheets. Drawing Plans, Elevations, Sections, Wall Types, Doors and Finishes Schedules.
- Structural sheets. Foundation and framing plans, member sizes, typical details, and general notes prepared through Structural CAD Drawing Services.
- MEP sheets. Layouts for Ducts, Pipes and Conduits, Riser Diagrams and Equipment Schedules.
- Specifications. Specifications in the writing form regarding materials, products, testing and workmanship.
They show design intent. In the structural plan, you will know that there is a W12x26 beam span from one column to another column and the load that the connection must take. Normally, it does not inform the fabrication shop about where the bolt holes will be placed. That level of detail is left to the people building it.
What Are Shop Drawings?
Shop drawings as described by AIA A201 are drawings, diagrams, schedules, and other information which have been developed for the work by the contractor or a subcontractor/supplier/manufacturer showing some aspect of the work. On a real job, that looks like this:
- Structural Steel Shop Drawing Services include piece drawings for each member, connection details, and erection plans.
- Rebar. Bar lists, bending schedules, and placing drawings.
- HVAC sheet metal. Duct layouts with fittings, joints, and hanger locations.
- Curtain wall. Panel layouts, anchor details, and sealant joints.
- Millwork. Elevations, sections, and hardware locations for casework.
In order to explain the difference between the two, an example would be the rebar. The structural drawings provide information such as bar size, spacing, and cover. The shop drawings of rebars contain all information related to the bar mark, length, bend, and position of placement for each bar.
That’s the common thread. Every dimension on a shop drawing is there because someone will build directly from the sheet.
How Do They Compare Side by Side?
The differences come down to who makes them, what they’re for, and what weight they carry:
| Construction drawings | Shop drawings | |
|---|---|---|
| Prepared by | Architect and engineers | Contractor, subcontractors, fabricators, suppliers |
| Purpose | Define the design and what will be built | Show how a specific part will be fabricated and installed |
| Level of detail | Design intent and typical details | Fabrication level: every piece, dimension, and connection |
| Contract status | Part of the contract documents | Not contract documents under AIA A201 §3.12.4 |
| When produced | Before bidding and construction | After award, during the submittal phase |
| Reviewed by | Owner and permitting authority | General contractor, then architect and engineers |
| Used by | Bidders, plan reviewers, every trade | One trade’s shop and field crew |
Why Aren’t Shop Drawings Contract Documents?
According to the AIA A201 §3.12.4, shop drawings, product data, and samples are not part of the contract documents. They are meant to indicate how the contractor will satisfy the requirements of the design and not amend the design.
This fact bears some consequences. For instance, if there is a duct shop drawing that avoids a certain beam, but no one notices it, the architect stamps the document. This does not formally approve the change because the architect reviews the submittal under §4.2.7 only to check whether it conforms to the design concept. If the contractor does not clearly identify a deviation during the submittal process, the contract drawings govern, and the responsible party bears the cost of correcting the work.
How Is the Submittal Process Done?
The process of shop drawing submittals is relatively similar for all cases from shop to design and vice versa:
- Preparation. The subcontractor or fabricator prepares them using the project drawings and measurements taken on site.
- Contractor review. General contractor examines coordination with other trades and compliance with the contract and signs them.
- Design review. Architects check them and send each one to an appropriate engineer.
- Return. The reviewer returns each submittal with a status such as “approved,” “approved as noted,” “revise and resubmit,” or “rejected.”
- Resubmittal. The team corrects anything that does not receive approval and sends it through the same review process again.
Under AIA A201 §3.12.7, teams cannot start work that requires a submittal until the appropriate party approves it, so a slow review cycle for steel or curtain wall can delay the entire schedule. The shop won’t cut until the stamp comes back.
Where Do Shop Drawing Mistakes Usually Come From?
The usual culprits are unglamorous:
- Outdated sheets. A detailer works from a superseded drawing or misses an addendum.
- Trade conflicts. Two trades each produce a correct shop drawing, but the duct and the sprinkler main both claim the same space. These coordination issues are a common reason teams use clash detection in BIM before fabrication starts.
- Field conditions. The building doesn’t match the drawings, like an existing beam sitting lower than the survey shows.
- Unflagged deviations. The team sends a substitution or reroute with the submittal without clearly identifying the change in writing.
The coordination problem is the one a model handles best. When teams combine each trade’s fabrication-level model, they can identify discrepancies before fabrication starts instead of discovering them after installation. This is LOD 400, wherein the model holds the same level of detail as that of the shop drawings.
How Are Shop Drawings Different From As-Built Drawings?
As-builts are a third set. As-built drawings record what the team actually installed, including field changes, and the team delivers them to the owner at closeout. Shop drawings come before fabrication, while as-builts come after installation. Teams often create as-builts by updating information from both the shop drawings and construction drawings.
Need shop drawings turned around without holding up the schedule? Optimar Precon’s detailers prepare shop drawings for steel, rebar, and MEP trades, checked against the latest contract set before they go out for review.
FAQs
The contractor, subcontractor, fabricator, or supplier prepares it, usually with a detailer assigned specifically to that task. The architect and engineers will check them but do not make them.
Not as contract documents. Under AIA A201, teams treat shop drawings as submittals. If a shop drawing conflicts with the contract drawings, the contract drawings govern unless the appropriate parties formally approve the change.
The architect reviews them, but only for conformance with the design concept. An approval stamp doesn’t relieve the contractor of responsibility for deviations it didn’t point out.
Under AIA A201 §3.12.7, work that requires a submittal cannot begin until the appropriate party approves that submittal.
