Curb and Gutter Grade Documentation for Road Construction

Curb and gutter grade documentation is a control point between subgrade and paving on road construction projects. A curb flowline that is out of grade creates drainage problems — ponding at high spots, excessive flow at sag points — and may require removal and replacement before the road can be paved. Documentation before and after the pour is what proves the work was done to grade.

Published May 28, 2026·8 min read

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Quick Answer

What documentation is required for curb and gutter grade on a DOT road project?

DOT curb and gutter grade documentation requires three records: (1) a pre-pour subbase elevation survey at the curb line on a 25-ft grid, confirming the subbase is within ±0.05 ft of the design curb subgrade elevation before forms are set; (2) a post-pour flowline elevation survey at 25-ft intervals and at all PC/PT points, sag points, and grade breaks, with deviations compared to the design profile and shown in a deviation table; and (3) a back-of-curb or top-of-curb elevation check at the same stations as the flowline survey, confirming curb height is within tolerance. State DOTs typically require the flowline deviation report to be submitted to the resident engineer before paving begins. Acceptable tolerance is typically ±0.04 ft for the flowline and ±0.25 inch for curb height.

±0.04 ft (most state DOTs)

Flowline elevation tolerance

±1/4 inch from design curb height

Curb height tolerance

25 ft standard; 10 ft at curves and sags

Survey station interval

Pre-Pour Subbase Survey at the Curb Line

The subbase elevation at the curb line determines whether the poured curb will achieve the design height and flowline. If the subbase is high at any point, the curb will be under-height at that point — and the flowline will be correspondingly high, causing water to pond at that location instead of flowing to the inlet.

Pre-pour survey procedure:

Calculate the design subbase elevation at each 25-ft station: design flowline elevation minus design curb depth (typically 7 inches for standard Type B curb and gutter).
Shoot the subbase at each station with a total station or GPS rover.
Compare measured to design. Flag stations where the subbase is more than 0.03 ft above design — these will produce a short curb and high flowline.
Correct flagged areas by cutting down or replacing the subbase material before the form crew begins work.
Document the corrected survey before allowing the form to be set.

Post-Pour Flowline Survey Requirements

The post-pour flowline survey is the QC record that the inspector signs off on before paving can begin. The flowline is the inside bottom of the gutter pan — it must drain continuously toward each inlet without high spots or flat spots that would allow standing water.

Location Type	Survey Interval	Why Closer Spacing
Tangent sections	25 ft	Standard interval for straight grades
Horizontal curves	10 ft	Cross slope and flowline vary through curve
Sag vertical curves	10 ft	Critical to catch flat spots at low point
Curb returns (driveway aprons)	At each edge and center	Match point must drain to road, not pond
Inlet locations	5 ft each side of inlet	Confirm grade breaks drain to inlet
PC and PT of horizontal curves	At PC and PT	Transition from tangent to curve grade

Acceptable Deviations and Corrective Action

When flowline shots exceed the tolerance, the options are limited and none of them are cheap:

Within ±0.04 ft: Typically acceptable without corrective action. Document the deviation and obtain inspector sign-off.
+0.04 to +0.10 ft (flowline too high): May be correctable by grinding the gutter pan. Confirm with the inspector that grinding is an acceptable repair before proceeding. Document grinding location and final elevation after grinding.
Greater than +0.10 ft (flowline significantly high): Removal and replacement of the out-of-tolerance section is typically required. Calculate the station limits of removal and obtain the inspector's agreement before saw-cutting.
Negative deviation (flowline low): Low flowline creates a channel that can collect debris. Minor deviations (up to -0.06 ft) may be accepted by the inspector as not affecting drainage function. Document and note in the record.

Documentation Package for Inspector Sign-Off

The documentation package submitted to the resident engineer or inspector for curb and gutter sign-off typically includes:

Flowline elevation deviation table — station, design elevation, measured elevation, deviation, and pass/fail for each survey station
Curb height deviation table at the same stations
Photographs of any corrective actions taken (grinding, replacement sections)
Post-correction survey results for any corrected areas
Inspector sign-off form with date, project, station limits, and inspector signature

Keep the signed curb and gutter QC record as part of the project documentation package. This record is your evidence that the curb was accepted before paving — if paving elevation issues arise later, the curb acceptance record proves the problem originated after your work was signed off.

Document Curb Grade Before Paving Begins

Sitemark captures flowline shots, deviation tables, and corrective action records in the field — assembled into a sign-off package before the paving crew arrives. Start free.