Shop drawings are the detailed trade-specific drawings created by the contractor, manufacturer and subcontractors to demonstrate the precise manner in which a component will be made, assembled and installed. A shop drawing that was either lost, outdated or never properly verified. This does not happen often. It is the everyday existence on thousands of construction sites and precisely the reason why the study of shop drawings is important to anyone who designs, constructs or funds a construction project.
This guide dissects all that a contractor, architect, engineer or project owner has to know: what exactly shop drawings are, who makes and accepts them, what types of shop drawings are used in various trades, why shop drawings are so important to the budgets and schedules and how the review process works to protect budgets and schedules.
What Is a Shop Drawing in Construction?
A shop drawing is a very elaborate technical drawing, prepared by a contractor, subcontractor, manufacturer or fabricator. This illustrates how exactly a particular element of the building will be made, assembled and fitted on site.
Unlike the design drawings, shop drawings are prepared by the architect, explaining how this particular part is to be built, not how a building should be built and not how it is supposed to work. It contains the dimensions, materials, tolerances, connection techniques and the sequence of assembly that must be followed by a fabrication shop or installation crew to have the job done right the first time.
Consider the set of drawings created by an architect as a recipe that describes the dish and its ingredients in a general outline. A shop drawing is the sequential cooking technique, which is written down in a manner that the cook must plate it. This degree of granularity is necessary for steel detailers, millwork shops, glazing contractors and MEP installers since the general design intent is not sufficient to drive a CNC machine or a welding crew.
The construction documents are issued by architects and structural engineers to outline the overall design. The contractors and suppliers react by translating such documents into production-ready instructions. That translation step is what a shop drawing is all about and it is one of the quickest methods of bringing costly mistakes to a construction project.
Shop Drawings vs. Construction Documents: Key Differences
Misidentifying these two types of documents leads to actual issues on actual job sites. Therefore, the differentiation is worthy of a sharp dissection as opposed to a loose analogy.
Design drawings or sometimes referred to as construction drawings, are created by the architect or engineering team. They provide a legal and technical foundation to the entire project, which includes layout, materials, code compliance and performance requirements. Such documents are included in the signed contract and all other drawings on the project should correspond to them.
One level further below is a shop drawing. It is manufactured following the issuance of the contract documents and it is typically manufactured by the party that produces or installs a certain component. It is much finer, frequently showing exploded views of assemblies, weld marks, bolt designs and precise tolerances in fractions of an inch or millimeters.
| Category | Construction Documents | Shop Drawing |
| Created by | Architect or engineer | Contractor, fabricator, or supplier |
| Main goal | Communicates design intent and code compliance | Communicates exact fabrication and installation steps |
| Level of detail | General dimensions and performance criteria | Exact measurements, tolerances, and connections |
| Used during | Permitting, bidding, and design approval | Manufacturing, prefabrication, and on-site assembly |
| Contractual status | Forms part of the legal contract documents | Supports the contract but does not replace it |
A single fact foams at the mouth of many a project manager: a shop drawing is not a legal substitute for the construction documents. In case of conflict between the two, the signed contract documents nearly always prevail and the fabricator should revise the shop drawing accordingly. It is the way in which minor variations become huge change orders that a shop drawing is treated as a casual drawing as opposed to a submittal that can be reviewed.
Who Creates and Approves Shop Drawings?
No one wants the architect to describe every weld on a steel frame and that is the very reason why this division of labor exists. Shop drawings are drawn by the individuals who are nearest to the manufacturing and installation process and not by the design team that created the building.
Who Prepares Them
The production of shop drawings is usually the role of:
- General contractors: Organize submissions of all the trades and ensure uniformity before submitting them to be approved.
- Subcontractors: Describing their particular extent, like HVAC duct routes, plumbing risers or electrical conduit layouts.
- Manufacturers: Provide fabrication drawings of pre-engineered items such as curtain wall systems, elevators or custom millwork.
- Fabricators and detailers: Translate structural design purpose into production-ready details of items that are assembled off-site such as steel connections and precast panels.
Who Reviews and Signs Off
After a shop drawing is created, it must be placed in a formal submittal and review process before anybody can fabricate it. It is checked against the design intent and against the code compliance by the architect or engineer of record. The project manager of the general contractor approves it as per the schedule and scope. In BIM-based projects, a BIM coordinator will execute a clash detection pass to identify geometric conflicts between the trades before they turn into physical conflicts on the field.
A shop drawing may only be able to support fabrication or installation legally after this chain of approvals has been done. The most avoidable causes of field rework include skipping a sign-off or construction on an outdated version.
Types of Shop Drawings Used in Construction
Not all trades are attractive in the same manner and it is that variety that makes shop drawings so versatile as a tool throughout a whole project. The following are the categories that are most frequently found on commercial and residential job websites.
Structural Steel Shop Drawings
These include beams, columns, braces and connection nodes, to the extent of bolt-diameters and weld symbols. Such a scale would not be possible without this degree of accuracy because at scale, all the members must fit their connection point perfectly.
Precast and Reinforced Concrete Shop Drawings
Facade panels, hollow core slabs and precast stairways require drawings that specify the locations of reinforcements, lifting points and the final sizes before a single yard of concrete is poured at the plant.
MEP Shop Drawings
Shop drawings in the mechanical, electrical, and plumbing systems are some of the most coordination-intensive on any project. They chart duct routing, pipe paths, conduit runs, and equipment clearances and they are needed to reveal clashes between systems before installation.
Millwork and Architectural Shop Drawings
Custom cabinetry, trim, stone countertops and architectural woodwork are based upon shop drawings to define reveals, edge profiles and finish details with a level of detail that would never be possible to define at full scale using a generic architectural drawing.
Curtain Wall and Glazing Shop Drawings
Facade systems are integrated structural, thermal and aesthetic thus a single assembly is created. Consequently, detailed shop drawings are unacceptable to scale up the panel, to place anchors and to detail how to weatherproof the system.
Why Shop Drawings Are Important in Construction
A construction project that lacks well-drawn shop drawings is similar to a ship being sent to the sea without a chart. The overall trend may be correct, but each reef and shoal is an unexpected event and not an expected danger and the unexpected on a construction site is always an expensive thing.
The numbers back this up clearly. A plan grid and FMI industry research revealed that 26% of construction rework is due to poor communication and the other 22% is due to incorrect or incomplete project information. Combined, the two factors, both of which shop drawings are specifically designed to correct, push almost half of all avoidable rework in the industry.
Individually, the Construction Industry Institute estimates typical direct field rework of between 5% of total project cost and a reported range of 2% to 20% based on project complexity and quality of coordination. Even the low end of that, on a commercial construction costing $20 million, would be a six-figure expense that could be largely avoided by a properly vetted shop drawing process.
This is what good shop drawings can provide throughout a project lifecycle:
- Clash prevention. Structural and coordinated MEP and structural shop drawings show conflicts between ducts, beams and pipes on paper rather than on site where a crew is standing about awaiting.
- Faster fabrication. Manufacturers and fabricators act under approved, clear instructions rather than guessing at the architect’s intent, reducing the production cycles.
- Fewer RFIs. A complete shop drawing provides answers to most of the field queries before they are even posed, reducing the cycle of request-for-information that delays schedules.
- Accurate cost control. Strict quantity takeoffs are supported by detailed bills of materials, making procurement and budgeting based on reality as opposed to estimates.
- Defined accountability. A shop drawing sign gives a good record of who signed what which would be vital in the event of a dispute or defect claim in the future.
What Should a Shop Drawing Include?
Take ten shop drawings of trades, all open and the format will be different but the constituents are hardly ever different. The reviewer is aware of what to look at and can identify a submittal that is weak in a few seconds.
| Element | What It Covers |
| Title block | Project name, sheet number, trade, date, and preparer contact details |
| Reference notes | Links to the related design drawing, detail number, and specification section |
| Dimensions and tolerances | Exact measurements for every component, plus allowable variance |
| Materials and finishes | Material grade, coating, finish, and approved manufacturer alternates |
| Connection details | Bolts, welds, anchors, and joints, coordinated with neighboring trades |
| Bill of materials | Itemized parts list with quantities and identification codes |
| Approval signatures | Sign-off blocks for the preparer, checker, and approving engineer |
Any submittal that lacks any of these items, particularly the bill of materials or the connection details, is likely to be returned with a “revise and resubmit stamp. Those days or even weeks, on a complex package are the reason why first time right is so important.
The Shop Drawing Review and Approval Process
A shop drawing that has not been carefully reviewed is similar to an unverified guess but in professional formatting. Design intent and field reality actually come into reconciliation during the review stage which follows a relatively standard regimen on most projects.
- Submittal preparation. The drawing package is compiled by the responsible trade, and is referred to the appropriate revision of the design documents, and passed through the general contractor.
- Initial coordination check. The general contractor or BIM coordinator filters glaring conflicts in other trades prior to the package being sent to the design team.
- Design team review. The architect or engineer of record verifies the drawing to the design intent, code requirements and the original specifications.
- Markup and disposition. The submittal is marked as Approved, Approved as Noted or Revise and Resubmit by the reviewers with certain comments attached.
- Resubmission if needed. Any reworked or recorded items are reworked and put through another review process until all are given full approval.
- Release to fabrication. Cutting, welding, casting or installing the actual component can only be done based on an approved shop drawing.
It is tempting to skip steps in this sequence under schedule pressure and it is also through how defects introduced during construction can find their way into completed buildings. In general, even a hurried approval does not save time as the rework that will follow is usually more expensive than the review would have been.
Common Mistakes That Undermine Shop Drawings
Experienced teams are not exempt from making foreseeable traps and the majority of them can be traced back to process discipline as opposed to technical expertise.
- Working from an outdated revision. Citing an outdated copy of the design documents forms an internally consistent yet initially incorrect shop drawing.
- Vague field-verification notes. An admonition that merely notes verification in the field without evidence and follow-up is likely to present as an actual issue during installation.
- Missing trade coordination. Describing a single system without verifying against a nearby ductwork, piping or structure is a primary source of physical clashes.
- Incomplete bills of materials. A bracket or fastener absent on paper translates to stopped production in the shop.
- Treating approval as a formality. Approving a submittal without a real technical review is like rubber stamping of a submittal.
Final Thoughts
Any successful construction, big or small, a retail fit-out or a forty-storey tower is reliant on an unspoken strata of documentation that hardly ever receives public accolade: the hatch of drawings that transforms architectural fantasy into something that can actually be constructed by a welder, a fabricator or an installer. This is what a shop drawing can truly provide, project after project.
The right way to do this process is not just because it adds paperwork to itself. It is regarding avoiding the type of $31-billion-a-year losses in the industry, predetermined by miscommunication and faulty data that can be prevented to a large extent with the help of better coordination. When the teams approach shop drawings as a strategic control, and not a bureaucratic control, they will always complete the projects with fewer RFIs, less rework and with more constrained budgets.
Knowing what a shop drawing is can help you wrap your head around complex construction blueprints. However, it won’t do much good when it comes to minimizing cost overruns. That’s where the Smart Constructs company jumps in. We help contractors, developers, architects, and project managers use precise shop drawings in a way that increases profit margin and bid approvals.
FAQs
What is a shop drawing?
It is primarily intended to convert overall design intent into precise dimensions, material and assembly specifications required by a fabricator or installer to construct a particular component properly.
Who does the shop drawings?
They are prepared by contractors, subcontractors, manufacturers and fabricators and are usually coordinated and presented as a complete package to the design team by the general contractor.
Are shop drawings a substitute for construction documents?
No. They assist in and expound on construction documentation. However, the signed contract documentation prevails in case of any conflict between the two.
What is the average time for the shop drawing approval?
The review of simple submittals can be cleared within a few days, whereas complex, multi-trade, coordinated packages may require several weeks based on complexity and turnaround by reviewers.
What is the consequence of not having a shop drawing approved before fabrication?
Milling based on an untested drawing is a risky way to manufacture parts that are not designed or in the field and can be very expensive to fix, delay and cause controversy over who is at fault.
