Shop Drawings vs Construction Drawings for MEP Projects

Drawing accuracy is crucial for each construction project. It defines the design intent, allows installing systems properly, and ensures all elements fit together perfectly. However, one of the most persistent questions in the industry is the difference between shop drawings and construction drawings. Although these terms are sometimes used interchangeably, there is no way these drawings can be considered identical in meaning and application. The purpose of construction drawings is to show the overall design intent, while shop drawings are responsible for implementation of individual elements according to the overall design. 

Understanding the difference between these drawings is essential for successful completion of each construction project. Especially in cases of complex MEP (mechanical, electrical, and plumbing) projects. The failure to differentiate these two kinds of drawings and misunderstanding of their purposes can cause errors, complications, and even additional expenses. So, regardless of your position (architect, MEP contractor, general contractor, fabricator, etc.), it is necessary to understand shop drawing services and construction drawing services.  

What are Construction Drawings? 

Construction drawings are fundamental project planning and design documents. They are usually prepared by architects and engineers at the design stage, following directions of property owners. Construction drawings contain the whole project design and are the technical basis of the entire project. 

Usually, a complete set of construction drawings consists of: 

• Floor plans;
• Elevations;
• Sections;
• Schedules with doors, windows, finishes, and equipment;
• Notes and specifications;
• Structural drawings with load-bearing elements, columns, beams, and foundations;
• MEP systems layouts;
• Site plan.

Construction drawings have many important functions. They are used for project cost estimation during the bidding process, as well as for ensuring the compliance with laws and industry standards. In addition, construction drawings are contract documents which make sure everyone understands the objectives of the project. 

Construction drawings are prepared at the pre-construction stage, in the process of design development. Construction drawings answer the question «What is being built?». 

What are Shop Drawings? 

As we have already mentioned, construction drawings are made in order to show the whole picture of the future project. However, to make certain elements of the project ready for fabrication, it is required to develop shop drawings. Unlike construction drawings, they give precise technical information about specific elements of a construction project. 

Shop drawings are typically developed by contractors, subcontractors, fabricators, manufacturers or other specialists after the signing of the construction contract. Each subcontractor develops shop drawings independently. Each of these drawings requires approval before fabrication begins. 

The level of detailing in shop drawings is much higher than in construction drawings. Typically, these drawings consist of: 

• Exact dimensions;
• Specifications of the material;
• Connection details;
• Instructions for assembly;
• Guidance on the process of installation of components;
• Tolerances;
• Reference numbers and exploded views;
• Assembly diagrams.

The standards of accuracy for shop drawings are much higher than for construction drawings. In order to make shop drawings contractors investigate the site and measure all dimensions carefully. The preparation process of shop drawings requires high attention to details because the quantity of detailing is bigger. 

Shop Drawings vs Construction Drawings: Detailed Comparison 

Here are the main features of these two kinds of drawings presented in the table: 

So, construction drawings show what will be built, and shop drawings show how it will be built, fabricated, and installed. 

Why the Difference Is Important?

As we have said, understanding the difference between these drawings is not only a theoretical problem. Confusing these terms is dangerous for the project and can cause a number of serious difficulties. 

If the design intent is misinterpreted during the fabrication process, the component won’t fit on the jobsite. If the importance of shop drawings as a coordination tool is underestimated, the clashes between MEP systems and structures remain undiscovered until the installation. And the results are the additional expenses, delays, and problems in relationships between project participants. 

Research done by the Construction Industry Institute shows that effective collaboration in development of shop drawings can reduce the amount of the rework costs up to 30%. On the contrary, inadequate cooperation leads to delays in approval process, mistakes in fabrication and on-site clashes. 

For the complex projects, especially MEP projects, distinguishing these drawings is important for preventing clashes and installation problems. MEP systems should be carefully coordinated with the architectural and structural elements of the building. Without accurate shop drawings, which correspond to the field conditions, there will be HVAC ducts hitting structural beams, pipes going through columns and conduits having no clearance. 

Detailed documentation is essential for the effective coordination between design and execution teams. Complete, clear and coordinated construction drawings form the basis for creation of shop drawings. Precise and coordinated shop drawings guarantee proper fabrication and installation of components. Here is the place where MEP modeling services can be useful for the process of coordination and detailing. 

The Role of Shop Drawing Services in Construction 

Shop drawing services are helpful when developing detailed instructions for fabrication. They allow making sure that the component, which will be fabricated in the factory, will be assembled properly on the job site. 

The main advantages of professional shop drawing services are: 

• Better coordination – Shop drawings allow verifying clearances, planning of installation sequence and preventing geometric or functional conflicts between the systems;
• Decrease in the number of RFIs – The presence of accurate and detailed drawings decreases the number of questions, which can appear during the process of installation;
• Faster approval – Shop drawings, which are developed according to construction drawings and project specifications are easy to approve;
• The increase in installation accuracy – Precise instructions help to assemble everything correctly and do not require any rework;
• The decrease in the number of field conflicts – Well-coordinated shop drawings identify possible clashes beforehand.

Shop drawing services are especially useful for the subcontractors and special vendors. They need to develop accurate instructions for manufacturing of components, which should be fitted within a larger system. These components can be anything from HVAC ducting to plumbing systems and electrical conduits. 

The Role of Construction Drawing Services 

Construction drawing services are needed for developing technical documents, which will define the scope of work and its technical requirements. These services form the foundation of the whole construction process. 

Complete, clear and coordinated construction drawings form the basis for the development of accurate shop drawings. Good quality of construction drawings simplifies the process of developing shop drawings. 

The main advantages of professional construction drawing services are: 

• Better communication of design intent;
• Precise cost estimation, which allows estimating the materials,laborand construction costs; 
• The compliance with building codes;
• Development of the foundation for shop drawings.

How MEP Modeling Services Aid in Both Drawing Types 

MEP modeling services close the gap between construction drawings and shop drawings through intelligent modeling of mechanical, electrical and plumbing systems. Such modeling aids visualization, helps with clash detection and promotes accurate detailing. 

The main advantage of MEP modeling services lies in clash detection even before the construction stage. By merging architectural, structural and MEP models, clashes can be detected and resolved in the virtual world. For example, it allows detecting clashes like HVAC ducts hitting structural beams, piping conflicts with columns, conduits without clearance and others. Clashes are detected and solved in the model and not at the construction site. 

MEP modeling services help with construction drawings and shop drawings in the following ways: 

• Higher quality construction drawings –modeledsystems offer accurate layouts for incorporation in the construction drawing set. 
• Better shop drawings – BIM models produce detailed shop drawings, thus saving time on manual drafting.
• Better coordination –modeledsystems help visualize how the work of different trades is interconnected. 
• Lower rework rates – solving clashes early saves you from additional costs associated with making adjustments at the construction site.

Some examples of MEP modeling applications include HVAC ducting coordination, piping routing, electrical conduit planning and plumbing systems incorporation. BIM-based MEP modeling is extremely helpful in complicated projects. 

Challenges Commonly Faced in Drawing Coordination 

Even though construction drawings and shop drawings are clearly distinguished from one another, there are still coordination problems. Common problems include: 

• Misinterpretation of design intent – in case shop drawing teams do not understand the construction drawings’ requirements.
• Failure in coordination between trades – in case each trade develops its shop drawings independently and without reviewing the interaction with other systems.
• Late revisions – in case design changes appear at the time of developing shop drawings.
• MEP system clashes – in case HVAC, electrical and plumbing systems clash with each other and/or with structural elements.
• Inaccurate dimensions or missing details – in case construction drawings contain inconsistent or inaccurate details for further shop drawing development.
• Approval delays – in case shop drawings have errors that require sending them for resubmission.
• Misinterpretation errors during fabrication – in case the shop drawings are not precise enough for fabricators to work from.

Such problems usually result from treating the review of shop drawings as an ordinary approval step. It is the gap between “what” (construction drawings) and “how” (shop drawings) where cost overruns and schedule delays tend to come from. 

Tips to Make Your Project Delivery Better 

Here are some tips to avoid coordination problems and make sure your project succeeds: 

1. Begin with clear and consistent construction drawings. Quality of construction drawings determines the efforts that will go into producing shop drawings. Thus, invest in professional construction drawing services.
2. Have experienced detailing teams produce shop drawings. Compared to construction drawings, shop drawings require much higher standards of accuracy. Experienced teams know how to translate design intent into details.
3. Start working with MEPmodelingservices early. Incorporate MEP modeling in the beginning to be able to detect and resolve clashes before the stage of developing shop drawings. 
4. Review and approve drawings before fabrication. Never start fabrication until you receive shop drawings that have been approved by all parties involved.
5. Have version control and revision tracking. As the project progresses, changes are inevitable. Thus, use some drawing management platform to track all revisions.
6. Have all drawings aligned with project specifications. Make sure that construction drawings, shop drawings and MEP models reflect project specifications.
7. Take shop drawing review as an opportunity to coordinate things.

Conclusion 

Construction drawings and shop drawings perform different but equally necessary tasks in every construction project. Construction drawings show the design intent and define what has to be built. Shop drawings describe how the components will be fabricated and installed. 

Both are necessary for efficiency, accuracy and low level of risks. Construction drawings lay the foundation. Shop drawings add precision. With both, successful project delivery is possible. 

In the context of complicated MEP projects, the distinction is particularly important. Professional shop drawing services, construction drawing services and MEP modeling services ensure accurate translation of design intent into details, early clashes detection and successful project completion on time and under budget. 

Frequently Asked Questions 

1. What is the difference between shop drawings and construction drawings?

Construction drawings represent design intent and show what has to be built. They are produced by architects and engineers in the design phase and include floor plans, elevations and general specifications. Shop drawings show how certain components will be fabricated and installed. They include exact dimensions, connection details and assembly instructions. Thus, construction drawings present the big picture while shop drawings present the execution plan. 

2. Who prepares shop drawings in a construction project?

Shop drawings are usually prepared by the party responsible for fabricating or installing the particular components. This may include subcontractors (like mechanical or electrical ones), specialist fabricators, manufacturers or independent detailing companies offering shop drawing services. In large scale projects, general contractor coordinates the submission of shop drawings from all trades. However, the actual preparation of these drawings is made by specialists with deep knowledge of the particular system. 

3. Are shop drawings required before fabrication?

Absolutely, yes. Fabrication should never begin until the shop drawings are approved. Having shop drawings makes sure that the components to be manufactured fit in the particular place of building and coordinate with other systems. Beginning of fabrication without approved shop drawings is highly risky practice that causes rework, material waste and delays in the schedule once the discrepancies were found. 

4. How do construction drawings support shop drawing services?

Construction drawings provide the basis for developing shop drawings. They provide design parameters, spatial constraints, material specifications and performance requirements. High quality construction drawing services produce coordinated and dimensionally accurate documents which simplify the process of creating shop drawings and minimize misinterpretations. The better the construction drawings, the easier the process of creating shop drawings. 

5. Why are MEPmodelingservices important for drawing coordination? 

MEP modeling services are vital since they allow having 3D visualization and clash detection before any physical work is performed. With MEP modeling services, intelligent models of mechanical, electrical and plumbing systems are created to identify clashes with architectural and structural elements at the design phase. Such approach makes sure that construction drawings and shop drawings are well coordinated across all trades and prevent any unexpected situations, reduce RFIs and eliminate costly rework caused by uncoordinated MEP systems. 

6. What is the role of shop drawings in reducing project errors?

Shop drawings play an important role in the reduction of errors by translating the abstract concepts into detailed and actionable instructions. They allow detecting dimensional inconsistencies, verify clearances, confirm connection methods and make sure that fabricated components will match real field conditions. Providing clear assembly and installation instructions, shop drawings eliminate guesswork on site and minimize misinterpretations of the design documents. With proper review process, shop drawings function as a quality control checkpoint which greatly reduces errors in installation. 

Looking for professional assistance with your project’s documentation? Camellia Buildtech offers professional shop drawing services, construction drawing services and MEP modeling services tailored to your project needs. Contact us at Camellia Buildtech to discuss your project’s needs!