What Is Redline in Construction?
Definition
A redline is a markup made in red on a construction drawing to indicate a change, correction, or as-built condition that differs from the original design. Redlining is the process of marking up drawings to document field changes, and redline drawings are a key input for producing as-built and record drawings at project close-out.
The term redline comes from the longstanding practice of using red ink to mark changes on construction drawings. Red was chosen because it stands out clearly against the blue or black lines of the original drawing. Redlines can indicate many types of changes: as-built conditions where the work was installed differently than drawn, corrections needed, design changes from the architect, or field modifications approved by the engineer.
Redline drawings are maintained throughout the construction process. The general contractor is typically required to keep a current set of redline drawings that document any deviations from the original plans. Each trade is responsible for marking up their redlines as work is installed. These redlines become the basis for the final as-built drawings submitted at close-out.
The quality of redline documentation directly affects the usefulness of the final as-built drawings. Redlines should be clear, legible, and include enough information (dimensions, notes, material callouts) for someone who was not on the project to understand what was changed and why. Sloppy or incomplete redlines result in as-built drawings that do not accurately reflect the constructed conditions.
Why It Matters
Redlines are the bridge between what was designed and what was built. They document every field deviation, which is critical for future maintenance, renovation, and emergency response. A building owner who cannot locate a hidden pipe or conduit because the as-builts are incomplete faces expensive investigation and potential damage during future work.
How HomeFloorPlan Helps
HomeFloorPlan replaces the paper redline set with digital redlining tools that every trade can use from their phone. As work is installed, field crews mark changes directly on the digital plans in real time. These digital redlines are automatically compiled, creating a living as-built record that is always current and never gets lost or damaged like paper plans.
Frequently Asked Questions
What is the purpose of redlining construction drawings?
Redlining documents changes made during construction that differ from the original design drawings. These redline markups create a record of actual field conditions and serve as the basis for producing as-built and record drawings at project close-out.
Who is responsible for maintaining redline drawings?
The general contractor is responsible for maintaining a current redline set. Each subcontractor is responsible for marking up changes to their own trade work. The GC compiles all trade redlines into a complete set that is submitted as part of the close-out documentation.