How to Redline the Set as You Build

Why this matters

No job gets built exactly as drawn. A water line drops under a beam nobody showed, a floor drain moves to clear a footing, a sleeve goes in where the slab crew could reach it. Each change is small, and each is invisible once the ceiling, wall or slab closes. The only reliable record of where things actually went is the one the crew writes on the drawings while the work is still open. Redlines written on the day are precise and cost minutes. Redlines reconstructed at closeout from memory are guesses, and the next person to cut into that slab trusts them anyway.

What happens downstream when nobody keeps them is covered in As-Builts and What Happens When Nobody Updates Them, and the basic markup habits in How to Mark Up a Drawing for the Next Tech. This card is the daily discipline that produces a record set worth having.

What a redline is, and what it is not

A redline is a hand markup on the field set showing a difference between what the drawings show and what was installed. The marked-up field set becomes the contractor's record of construction, which the spec commonly requires at closeout under Division 01 (MasterFormat 01 78 39, Project Record Documents, where the project uses that numbering). The design team or the contractor then turns those redlines into the as-built or record drawings.

A redline records a change. It does not authorize one. A moved floor drain should exist on paper first as an answered RFI, an architect's supplemental instruction, or a written direction, and the redline cites that document. A redline with no authority behind it records that the crew departed from the drawings on their own, which is not a record you want to be the author of. See related: The Paper That Changes a Job: RFI to Change Order.

The color convention, and why to ask

A common convention: red for additions and changes (what was built that the drawing does not show), green for deletions (what the drawing shows that was not built), and sometimes yellow highlight over work installed exactly as drawn, so the reader can tell "built as shown" from "not reviewed yet." It is common, not universal. Some GCs use blue for comments or questions, some reverse red and green, and some specs prescribe their own. Ask the GC on day one, read the record-documents section of the spec, and write the convention in the corner of the cover sheet of your field set so a new crew member does not invent one.

If the set is electronic, the same rules apply to markup layers and colors, and the file has to be saved somewhere the whole crew uses, not on one tablet.

Two days of redlines, worked

Tuesday and Wednesday on a tenant improvement, plumbing plan P-201. Three changes, each from a real cause, each marked before close-in.

 A. REROUTE  cloud, "10/14 JM, RFI 012"
    drawn:  =========================  1 in CW
    built:  =========+         +======
                     |  BEAM   |
                     +=========+
                     8 in lower under beam

 B. MOVED DEVICE  cloud, "10/15 JM, RFI 014"
    FD-2:   x drawn (struck)      o built
            |<----- 18 in E ----->|

 C. ADDED DIMENSION  cloud, "10/15 JM"
    grid 3 |<--- 6'-4" --->| 4 in sleeve, CL
    grid A  ... 2'-10" N to sleeve CL

A, the reroute. The 1 in cold water line was drawn running straight along grid B. In the field a beam sat 4 in lower than the structural drawings showed, so after RFI 012 the line dropped 8 in to pass under it and came back up. The redline strikes the drawn segment with a single line (so the original stays readable), draws the built route in red, notes the 8 in drop, and clouds the area. Inside or beside the cloud: date, initials, "RFI 012." Two more notes belong here, because they are what the next tech needs: the dip is now a low point in the line, so if a drain valve was added there, mark it; and if not, write "low point, no drain."

B, the moved device. Floor drain FD-2 was moved 18 in east to clear a footing, per RFI 014. The drawn symbol is struck, the drain drawn at its built location, and a dimension from the old to the new location added inside the cloud. That relative dimension is not enough on its own, because the drawn location was never dimensioned either. So the redline also carries the built center from two grid lines, 9'-2" east of grid 3 and 4'-6" north of grid A, which is the pair of numbers someone looking for that drain will actually use.

C, the added dimension. A 4 in sleeve was cast into the slab for future work, not shown on the drawing at all. Concealed in concrete, it will be found again only from the record. It gets two dimensions to its center line, each from a grid line: 6'-4" east of grid 3 and 2'-10" north of grid A, plus its size and what it is for if known. The cloud and date mark it as a field addition.

Note the order on Wednesday: FD-2's position and the sleeve were measured and photographed with a tape in frame before the slab pour, not after. A sleeve dimensioned after the pour is a dimension to a guess.

What must be dimensioned from a fixed point

A dimension is only as permanent as the thing it is measured from. Use, in this order of preference:

• Grid lines (through the column centers), because every discipline's drawings share them. See related: How to Find Your Place by Column Grid and Key Plan.
• Structural column centers or faces, stating which.
• Exterior walls and structural walls, to a stated face (finished, or face of stud, or face of block).
• Finished floor, for heights and depths.

Never dimension from a partition that a future tenant may remove, from equipment, from a fixture, or from another pipe. Those move or disappear, and the dimension dies with them.

What needs a fixed-point dimension at minimum:

• Anything concealed or buried: under-slab piping, sleeves, in-slab conduit, buried lines outside. Two horizontal dimensions plus a depth (below finished floor, or below finished grade).
• Anything relocated from the drawn position, like FD-2, because the drawing's position was approximate even before it moved.
• Valves, cleanouts, junction boxes and dampers above hard ceilings, so someone can find the access without opening the wrong section.
• Any change in elevation, like the 8 in dip, because elevations are invisible in plan.

The routine that keeps the set current

1. One field set is the record set. It lives in a known place on site, dated on the cover, and nobody takes it home. Personal copies are for reading; only the record set gets redlines. What breaks if you skip it: three partial sets, each right about different things, and nobody sure which to transfer.
2. Mark the same day, before you leave. The crew lead spends ten minutes at the end of each shift on what changed today. A change marked the same day is measured; one marked a week later is remembered. What breaks if you skip it: the dimension becomes "about there."
3. Before anything is covered, mark and photograph it. Before the slab pour, before the drywall, before the ceiling tile goes back. Inspections often coincide with these moments, which makes a good trigger. What breaks if you skip it: a concealed item recorded from memory after concealment.
4. Cloud, date, initial, cite. Every change in a cloud, every cloud with a date, the initials of the person who marked it, and the RFI or instruction number if there is one. What breaks if you skip it: a redline nobody can trace to a reason or a person when the engineer asks about it.
5. Strike with one line, never erase or white out. The record has to show what was drawn and what was built. What breaks if you skip it: the designer cannot see what changed and has to compare against another set.
6. Weekly, the office or the GC reviews the set. A quick review catches a missing dimension while the work is still open. Many GCs check the record set with each pay application. What breaks if you skip it: missing redlines are found at closeout, when the slab is a year old.
7. Mark revisions when new sheets arrive. When a revised sheet replaces one in the set, transfer every outstanding redline to it before the old sheet comes out, or keep the old sheet with the redlines and mark it superseded. What breaks if you skip it: a revision silently erases two weeks of record. See related: How to Confirm the Truck Set Is Current.

Where redlines go wrong

• A change marked without a dimension. A red line across a sheet says the route changed, not where it went. Every built position that differs from the drawing gets a number.
• "Field verify" written on the redline. That phrase belongs on design drawings; on a record it means the person who could have measured did not.
• Marking only the big changes. A crew that redlines reroutes and not moved cleanouts produces a record that is right where it does not matter much and wrong where a future tech will dig.
• A redline with no authority. If a change has no RFI or instruction, stop and get one before the work is concealed, then mark it.

How to check your record set

Pick three changes at random from the last week and ask whether someone who never saw the job could, from the set alone, walk to each item, find it within a few inches, and know why it is where it is. Then check that every cloud carries a date and initials, and that every concealed item carries two fixed-point dimensions and a depth. If the sleeve from the example could be found again from the set by a core-drilling crew five years from now, the set is doing its job.

References

• Division 01 of the project specifications, record documents section (MasterFormat 01 78 39 where used), for required format and color conventions
• See related: As-Builts and What Happens When Nobody Updates Them
• See related: How to Mark Up a Drawing for the Next Tech
• See related: How to Assemble a Closeout Package
• See related: The Paper That Changes a Job: RFI to Change Order