Red line drawings are a crucial part of the architectural design process. They serve as a quality control measure, allowing architects and designers to review and make changes to construction drawings before they are used by contractors to construct a building.
In this article, we will explore the importance of red line drawings, the process of “picking up redlines,” and how they provide a valuable learning opportunity for emerging professionals in the field.
We will also discuss tips and best practices for working with red line drawings, including how to keep track of changes and how to approach the task of reviewing and making changes to these important documents.
What is a red line drawing?
In short, a red line drawing is a type of architectural drawing that has been reviewed and marked up with errors, changes, and revisions.
These markups are typically done in red ink, making them easy to find. These drawings are used as a quality control measure in the process of creating construction drawings, allowing architects and designers to review and make changes before they are used by contractors to construct the building.
During the design and construction phase of a project, there are multiple instances when a member of the design team is handed over a set of drawings to be reviewed. And more often than not (especially in the early stages of a project), there will be areas that require further coordination and therefore alteration of the drawing.
These alterations are usually marked with a red pen to make them more visible – creating what is commonly referred to as a “red line drawing”. Producing precise and clear working drawings for an architectural project is not as simple as one might think. And completing a perfect drawing on the very first attempt is near to impossible.
It requires the input and collective expertise of many people in order to produce a complete set of construction drawings and for newly qualified architects and students, it may take many years of experience to master.
But carrying out red line amendments is an excellent way to learn and grow – where it is often a right of passage before taking on your own projects.

Why are red lines needed?
As mentioned above, creating a well-coordinated and complete set of construction drawings, especially on the first try is almost impossible. More often than not, you will need to revise these drawings and re-draft them several times over, to address both minor and major changes.
There are various factors that influence the use and requirement for red line drawings such as:
Self-checking
After drafting a design, it is advisable for the draftsmen to go over the drawing themselves before handing it over to a senior team member for examination. While going over the draft, you yourself might find a mistake that had previously been overlooked.
Once detected, the mistake can be highlighted with a red line and a new draft can be created.
One thing to keep in mind is that finding mistakes in your drawings is nothing to be ashamed of. When drafting a design, you may miss blatant mistakes simply because you have been looking at the same drawing for a very long time. So it is advisable to take a break and go through the drawings again after some time.
Printing the draft and creating your own red line drawing can prove very efficient in this regard.
Feedback
As mentioned, a draftsman may make various mistakes while producing a set of drawings and often these mistakes are pointed out by a senior architect or supervisor through red lines after they assess the drawing.
The red line drawings are then given back to the draftsman who redraws the drawing along with the changes. This feedback could be related to policy compliance, a design change, or simply a drawing error.
Client-requested changes
Fulfilling the client’s design brief and requests regarding the design is always the top priority for the design team. Even if that means adding last-minute changes. Once an architect has completed the project drafts, they discuss the design and requirements with the client. The client might then suggest additional amendments to the design which the architect will usually highlight in red pen.
Unexpected on-site changes
As architects we often face unforeseen situations on-site that might require a change to the current design. It could be anything ranging from a slight drawing error to a non-compliance with city building codes.
In these situations, an architect has to revise the design and create a new drawing using a red line.
City Requirements
Depending on where you are located, each city and area has distinct requirements for its buildings and structures, and often might ask the architect to make changes in accordance with these. This may lead to various minor alterations in the design.

Why are red line drawings useful?
Red line drawings are an essential part of the design process and have various uses that are not just limited to the ongoing design process. For example, red line drawings are useful…
As a learning tool
For anyone new in the architectural field, red lines drawings are a goldmine of knowledge. By going through the red line drawings of experienced professionals, you can learn what mistakes are commonly made, and how to catch and fix them.
To ensure proper designing
Architectural drawings are the foundation of a project and if any errors are left in these drawings, they can translate into the built form and cause a lot of damage during construction.
red line drawings ensure that all mistakes are caught and fixed, aiming to safeguard the construction process as much as possible. It is much more feasible to make changes on paper than to make changes on-site.
To track changes
Red lines are essentially the layers of changes that a design goes through in order to reach its final form. Hence, going periodically through these red lines can help you keep track of exactly what changes have been made in the design since it was started. These red lines may prove to be an essential tool in understating an architect’s design methodology and process.
Who are they for?
While several people benefit from red line drawings (for example, the client, the contractor, and the senior architects, etc.), they are primarily meant for the draftsmen. Once an error or alteration has been pointed out in the drawings, the architect then conveys them in detail to the draftsman.
This helps the draftsman in creating a newly revised and improved set of drawings .
How should you use them?
While there is no dictated way to use an architectural drawing. There are a few steps to follow when you are given a red line drawing to redraft.
- Go over the drawing in detail and make sure that you understand every single suggestion made.
- In case a few things escape your understanding, ask someone more experienced to explain them to you. Once understood, you can start redrafting the drawings.
- While making changes it is possible that you might miss a couple of errors. In order to avoid this, make sure to cross out each section that you have amended with a black marker (or any other marker that stands out against the red highlights). By doing this you ensure that all of the suggested adjustments have been made.

What is the difference between as-builts and redline drawings?
As-built drawings are the final set of drawings and specifications that reflect how a building was actually built. These documents are created after the construction process is completed, and they serve as a record of the actual physical layout and features of the building.
They include details such as the location of electrical and plumbing systems, the size of rooms, and the types of materials used. As-builts are important because they provide a clear understanding of the building’s actual physical characteristics and can be used for future reference and maintenance purposes.
They are generally provided to the building owner after the completion of the construction project.
Are they the same as redline drawings
No, as-builts are not the same as redline drawings. Redline drawings as discussed above, are the original set of drawings that have been marked up to reflect changes made during the construction process. They are used to document changes that occur during the construction of a building.
As-builts, on the other hand, are the final set of drawings and specifications that reflect how a building was actually built. They are created after the construction process is completed and provide a record of the actual physical layout and features of the building.
It is important to understand the difference between the two, as redlines may not always reflect all changes made by different contractors, and as-builts should be used when troubleshooting projects that are still in construction.
The general contractor may reconcile all redlines into a single document set, but if redlines from multiple contractors conflict, the GC may just pick one of the redlines instead of reaching out to both contractors. It’s important to ensure that you are working on as-builts, not redlines, when troubleshooting projects to avoid confusion and wasted time.
To sum it up
Red line drawings are an imperative part of the design process and help ensure the successful completion of any architectural project. If you are new in the profession, make sure to go through the annotated drawings of other architects to strengthen your own understanding. And always make your own red line drawings before handing them over to a senior.
Paying attention to these drawings will not only prove advantageous for you but will also save everyone on the team a lot of time and money by avoiding last-minute changes on-site.
FAQ’s about redline drawings
What does redline mean in engineering?
In engineering, “redlining” refers to the process of marking up original drawings, plans or specifications to indicate changes or revisions that have been made during the design or construction process. This is typically done using a red pen or other red ink, which is why the process is called “redlining.”
The redlines are used to indicate the changes made to the original document, and they help to ensure that everyone involved in the project is aware of the changes and is able to implement them correctly. It’s used to help identify and track changes made during the construction process and can be used to ensure that the final product is built according to the intended design.
What is a red line markup?
A redline markup is a set of notations, lines, or other marks that have been added to an original drawing, plan, or specification to indicate changes or revisions that have been made during the design or construction process. These marks are typically made using a red pen or other red ink, which is why the process is called “redlining.”
Redline markups are used to indicate the changes made to the original document, and they help to ensure that everyone involved in the project is aware of the changes and is able to implement them correctly.
They are commonly used in construction and engineering projects, and they can include notations on changes to dimensions, equipment locations, materials, and other details. They can also include new or modified drawings and notes that have been added to the original document.
How do you redline a plan?
There are several ways to redline a plan, but the most common method is to use a red pen or other red ink to make notations, lines, or other marks directly on the original document. Here are some steps that can be followed to redline a plan:
- Obtain a clean, clear copy of the original plan.
- Review the plan carefully and make note of any changes or revisions that need to be made.
- Use a red pen or other red ink to make notations, lines, or other marks on the plan to indicate the changes or revisions.
- Make sure to clearly label each notation or mark, and include any relevant information such as the date and the name of the person making the change.
- Double-check the redlined plan to make sure that all changes have been properly documented and that the notations are clear and easy to understand.
- Make additional copies of the redlined plan and distribute them to the relevant parties involved in the project.
- Keep an electronic copy of the redlined plan, in case it needs to be referred in the future.
It’s important to note that some companies and organizations use specialized software to redline documents electronically, with the advantage of being able to track changes and access the documents remotely.
It’s also important to keep in mind that redlining is a critical step in the construction process, as it helps to ensure that the final product is built according to the intended design, and allows the team to identify and track changes made during the construction process.
How do you redline a drawing in CAD?
Redlining a drawing in CAD (computer-aided design) is a bit different than redlining a paper drawing, as it is done electronically. Here are some steps that can be followed to redline a CAD drawing:
- Open the CAD drawing in the appropriate software (such as AutoCAD or Revit).
- Review the drawing carefully and make note of any changes or revisions that need to be made.
- Use the appropriate tools in the software to make notations, lines, or other marks on the drawing to indicate the changes or revisions. Some software’s have specific tools for redlining such as “redline” tools, “comment” tools or “markup” tools.
- Make sure to clearly label each notation or mark, and include any relevant information such as the date and the name of the person making the change.
- Double-check the redlined drawing to make sure that all changes have been properly documented and that the notations are clear and easy to understand.
- Save the redlined drawing with a new file name to indicate that it has been redlined.
- Distribute the redlined drawing to the relevant parties involved in the project.
It’s important to note that some CAD software also allows to track changes with a revision history and even to compare different versions of the drawing. Some software also allows to create a pdf file with the redlines, comments and markups, making it easy to share with non-CAD users.
Redlining a drawing in CAD has the advantage of being able to track changes, access the documents remotely, and make changes quickly and easily.
It’s also important to keep in mind that redlining is a critical step in the construction process, as it helps to ensure that the final product is built according to the intended design, and allows the team to identify and track changes made during the construction process.
What is redlining in interior design?
In interior design, redlining refers to the process of marking up original floor plans, elevations, or other architectural drawings to indicate changes or revisions to the design of a space. This process is similar to the one used in construction and engineering, where redlines are used to indicate changes that have been made to the original document.
Interior designers use redlines to indicate changes to the layout of a space, the location of furniture, electrical and lighting fixtures, and other elements of the design. They can also be used to indicate changes to the materials, colors, and finishes used in a space.
The redlining process can be done using a red pen or other red ink to make notations, lines, or other marks directly on the original document, or with specialized software that allows designers to redline a drawing electronically, with the advantage of being able to track changes and access the documents remotely.
It’s important to note that redlining in interior design is a critical step in the design process, as it allows the team to identify and track changes made during the design process, and it helps to ensure that the final product is built according to the intended design. And also it allows the client to see the changes and approve them before the construction process starts.