Shop Drawings vs Construction Drawings: What’s Different?

by Alexander Fraser

Drawings play a massive role when it comes to the construction industry. The drawings help to convey what the owner wants to build. 

The engineers and contractors are responsible for making the owner’s dreams a reality. Engineers create construction drawings while contractors create shop drawings. 

You’re probably wondering, “what are shop drawings?” In this article, we will look at shop drawings vs construction drawings. You’ll learn about each and its significance in a project.

When glossing over a set of shop drawings, you might think they are just like the construction set. Look closer and you will find that there are some details that differ from the engineer’s drawings. 

Contractors are required to perform a thorough investigation of the construction site for their shop drawings. With this information, they can create a set of drawings that accurately represents how the contractor will perform the work. 

There’s a ton of coordination that goes into creating the shop drawings. This is coming from the perspective of the contractor.

Don’t get me wrong; engineers also have a lot of work to create their design drawings. They are unable to get everything correct. So, they rely on the contractor to verify the site for their shop drawings. 

In this article, we will cover the difference between shop drawings and construction drawings. We will also look at the types of drawings in detail. 

I will cover the following topics in this article: 

What Are The Differences Between Construction Drawings and Shop Drawings?

Here I will cover five differences between construction drawings and shop drawings. We will look at the following:

  • When to Use the Drawings in the Construction Process
  • Who Creates the Shop Drawings vs Construction Drawings
  • The Accuracy of Each Type of Drawing
  • The Details of the Shop Drawings vs Construction Drawings
  • The Purpose of Each Type of Drawing

When to Use the Drawings in the Construction Process

Construction Drawings

An engineering firm would create construction drawings for a project owner to release to contractors to bid on. They will finalize the drawings before the actual construction work. 

In the construction industry, there are a few names for drawings. They can also go by:

  • Bid Set Drawings
  • Contract Drawings
  • Architectural Drawings
  • MEP Drawings

Occasionally, a permit set will be released for contractors to bid on. These drawings still need to go through a review by your county. Things may change, and the engineer will display the changes in the construction drawings. 

One project I worked on had many changes from the permit to construction set drawings. As a result, we had to submit a decent size change order to the general contractor. 

Shop Drawings 

You’ll want to finish your shop drawings before actual construction begins. 

As the contractor, you should verify the existing site conditions and design to satisfy the project design intent. You’ll develop shop drawings which will be the closest representation for the construction work.  

You will send the shop drawings to the engineer of the project for their review. Once you have approved shop drawings, you’re ready to build. 

Who Creates the Shop Drawings vs Construction Drawings

Construction Drawings

The architect or engineer will create the construction drawings. A project owner typically consults a firm when they want to build something. 

The owner may issue an request for proposal (RFP) to different design firms to bid on as they do with contractors. 

Based on the RFP, a team of design professionals will develop a set of plans which meets the owner’s requirements. They will also conduct job site visits to determine how they can satisfy the owner. 

Occasionally, engineers will create the entire design from the as-built drawings. Doing this creates issues for the contractor who will perform the work. 

It results in many RFIs as the drawings need to be more accurate and will result in changes to the design. Changes to the plans after the contract award means change orders for the contractor. 

You’ll surely upset the customer if you have any change orders they must fulfill. 

Shop Drawings

The contractor makes the shop drawings. Working for a mechanical contractor, we create a set of drawings for all plan and spec projects. 

As the contractor, you are responsible for ensuring the finished product functions correctly. It requires a lot of time to review the job site, the equipment selected, and the constructibility of the design. 

Regarding construction, the contractor is entitled to perform the work most cost-effectively. They satisfy the contract as long as they meet the plans and specifications. 

The contractor will review the design, applying their expertise and knowledge of the job site to the shop drawings. 

If you find more efficient ways to construct something, the shop drawings are where you’ll show that. 

Overall, the shop drawing will be like the construction drawings, but with minor changes throughout. 

The Accuracy of Each Type of Drawing

Construction Drawings

As mentioned earlier, the engineer or architect will visit the site to view its conditions. Their findings will guide the development of the construction drawings during the design phase. 

The engineer will do their best to design based on the existing conditions. The drawings they provide may be less than 100% accurate, but they act as a guideline for construction. 

Sometimes the drawing scaling might be incorrect, or they miss concealed items. 

That is where your contractor will come in and make their shop drawings. 

Shop Drawings

As the contractor, you will conduct a thorough investigation of the job site. You will need to take exact dimensions, look at potential issues with the design, confirm clearances, etc. 

All these items will be required when developing the shop drawings and to validate the design.

The only drawings that are more precise than shop drawings are your as-built drawings. 

The contractor makes as-built or record drawings at the end of a job. They will mark up their shop drawings with redlines during construction to show any changes made in the field. 

You must create a final version of the shop drawing incorporating all the markups. These will be your as-built drawings to submit with the closeout documents. All closeout construction documentation will go to the project owner. 

The Details of the Shop Drawing vs Construction Drawing

Construction Drawings

As mentioned earlier in the article, construction drawings act as guidelines for construction. So, there may be details that may not work with the site conditions. 

Engineers and architects must develop their drawings in a timely manner. They won’t be able to see everything on a project. 

They rely on the contractor’s shop drawings to correct any deficiencies with the design. 

There may be many issues if you have an engineer who only bases the design on as-built plans. You’ll send multiple RFIs in the project to confirm the design intent. Their answer will provide you with detailed information needed to finalize your shop drawings. 

Shop Drawings

The contractor will conduct site visits to understand how the building system operates. As a mechanical contractor, performing this step will aid you greatly. 

Understanding the different systems allows you to validate the design. For example, you can suggest modifying the pipe size based on the design flow requirements. If the pipe is too small, you won’t meet the required flow for the system. 

Overall, the changes I see made in the shop drawings are minor. You should implement them when you either find a better solution or need to correct the design. 

An Example of Construction Drawings vs Shop Drawings

The image below is from the construction drawings where we needed to replace a chiller. 

shop drawing vs construction drawings construction drawing chiller drawing what is a construction drawing MEP drawing what is a shop drawing shop drawing vs construction drawing construction drawing vs shop drawing

There wasn’t anything wrong with the design, but we felt that we could make some modifications to it. 

Instead, we shifted the chiller, moved the location of the pump, and changed the piping. See a shop drawing example below.

shop drawing vs construction drawings Shop Drawing Changes from construction drawing to shop drawing what is a shop drawing shop drawing vs construction drawing construction drawing vs shop drawing

Here’s the reasoning behind why we made these changes. 

  1. We wanted to install the pump in a new location to complete the work before the existing equipment went down. The goal is to reduce the duration of the equipment outage. 
  2. We moved the chiller location on the floor plans to meet the recommended clearance around the equipment. Restricting the clearance would make the chiller a challenge to maintain. 
  3. We adjusted the piping due to the new placement of the chiller and pump. 

We only wanted to benefit the building occupants and improve the design. That is the type of changes you want to include in your shop drawings. 

What is a Shop Drawing in Construction? 

The contractor creates shop drawings to represent how they plan to perform the work. The contractor will use and modify the construction drawings as they see fit. Conduct numerous site investigations to validate the design and show this in the shop drawings. 

Your main objective with shop drawings is verifying the design will work. Fix any issues found and show them as needed. 

Finding Clashes in the Design

One responsibility of the person working on the shop drawings is clash detection. 

There are times in the design when collaboration issues occur. As a result, some of the various trade’s work may interfere with one another. 

When this occurs, someone will need to change the route for their pipe or find the new exact location of the equipment. Notify the engineer of the issues as you find them. 

The person working on the shop drawings (often called the drafter) is responsible for identifying this. It’s not their sole responsibility, but it does help the team when they’re looking for these items. 

I always prefer to resolve something during pre-construction rather than in the field. 

Are Shop Drawings Always Required?

Only some projects will require you to make shop drawings. The project manager usually decides to complete shop drawings. 

To simplify, you should create shop drawings if your project’s contract documents contain plans and specifications.

The specs will mention what submittals to complete for the project. Shop drawings will be in the list of required submittals. Know that only some trades must submit shop drawings. 

What are Construction Drawings?

An architectural or engineering firm will provide construction drawings to display how to construct something. They release the plans with a construction RFP for contractors to bid on. These drawings will act as the guidelines for how to complete the work. 

A project owner will ask an engineering firm to provide a design to meet their needs. They will then work on multiple sets of drawings going through various stages of submittal reviews. 

During the design stage, you’ll have the following steps for a drawing set:

  • 60% Design
  • 90% Design
  • 100% Design
  • Final Design

Once the final design set is approved, the owner will release it for bidding. 

Contractors will use their best judgment while estimating the work. Any changes that occur with the design following the project award will result in a change for the contractor. 

The project owners rely on engineers and architects to produce accurate drawings. A mistake in the design may also cost these firms money so the contractor can complete the work. 

As a contractor, you often refer to the contract drawings when any out-of-scope work is in question. 

It’s good to get familiar with the drawings and review the them in their entirety. As a project manager, you must ensure your work jives with the other trades. 

Do Shop Drawings Superseded Contract Drawings?

Shop drawings will only supersede the contract drawings once approved by the engineer of the construction project. The engineer is responsible for ensuring the contractor understands the design intent with their drawings. Additionally, any modifications made to the design needs to comply with local codes and industry standards. 

Remember that the shop drawings will go through various stages during their development. The drawings won’t be final on the first iteration. 

The construction management and superintendent must review the shop drawings. 

Your project manager will look to ensure the scope of work is in the drawings. The superintendents will look for installation issues with the design. Identify any issues before submitting them to the engineer for review. 

While the drawings are in development, your team must know the drawings are not ready for construction. 

A note somewhere on the drawings will be sufficient. Just make sure it is noticeable. 

Conclusion

Construction and shop drawings hold a vital role in the construction industry. Depending on your company, you may only deal with construction drawings. 

Working for a mechanical contractor, our primary focus is the mechanical shop drawings. Making sure they’re accurate for the field crew is a challenge. 

If you’re required to produce shop drawings, you should work closely and collaborate with your team. 

You’ll have your drafters who will work diligently with a BIM model to provide you with the drawings. Also, talk with your superintendents when you have questions. I haven’t run into a superintendent that didn’t want to help me learn their trade. 

Preparing shop drawings is a team effort at the end of the day. It will benefit you greatly to have a good set of drawings. It will eliminate questions from the field and prevent project delays during the construction phase. 

With our many digital platforms, creating, viewing, and maintaining shop drawings has never been easier. The evolving technology in this industry is only making construction processes more efficient.  

Before you go, I suggest you check out my article on “What is a Construction RFI.” When issues arise with the design, you’ll need to resolve them using an RFI. It will go to the engineer or architect to provide a response and correction. 

Thank you for reading. 

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2 comments

Keith Palazzolo June 7, 2023 - 10:22 pm

In the over 35 years in the HVAC field I found most construction plans either didn’t have accurate measurements or where lacking in information.
Most common issue is with the steel work.
If the plan calls out for me to maintain a certain bod measurement but their is steel in the way who’s bos is lower than the call out I can’t possibly make it work.
So I send in a need for clarification report and it takes weeks to even get a call back about the problem, a delay in the finish date is enviable.
I’ve had projects delayed waiting for answers.
Once I had a change of equipment caused by the wrong equipment being specified, the steel work that the equipment is sitting on needed to be completely changed. This caused a massive delay because the steel workers were off the site. New steel was designed. Old steel needed to be removed and new steel installed. All while the project was handed over to the owners. Steel was completed and we were sent out to the job the install the equipment, but the Twin Towers were attacked and all of Manhattan was shut down for months as the project was located a short distance away. By the time we where able to get back into the city and start the install all over again the other trades had closed up the section of the ceiling that was were the equipment was being hung. GC had to hire a demo company to open the ceiling. It took us two days to install the equipment, one day to do control wiring, the electricians didn’t finish their work, and one day to get the electricians back to do the power. Then almost two days to do t&b. Another week for the carpenters and drywallers to do their work, another week for painting & finish trim.
Then I had to turn in as-builts.
All because no one wanted to be told they made a mistake.

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Alexander Fraser June 11, 2023 - 7:09 am

Thanks for sharing, Keith! I too have noticed that I can’t rely fully on the construction set drawings provided for the project. Typically find it’s best to field verify where you can. I spend a lot of time working on correcting design issues by submitting RFIs. It can be such a headache at times.

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